AMMTIAC Quarterly, Vol. 6, No.1 - Advanced Materials ...

V5N1 2010Past IssuesWe welcome submissions related to materials, manufacturing,and testing. If you would like to contribute,please e-mail ammtiac@alionscience.com.V5N3 2010V5N2 2010V5N1Feature Article: Low Pressure Cold SprayConductive Coating – A Case StudyTechSolution 15: A Definitive Guide toAccelerated Testing3rd Article: Properties and Applications ofRhenium and Its AlloysV5N2Feature Article: Automating Aircraft Inspections: Time andCost Saving Measures for the Inspection of Large AreaAircraft SurfacesTechSolution 16: Selecting a Nondestructive TestingMethod, Part VII: Acoustic Emission Testing3rd Article: New Technical Resource for Scientistsand Engineers: Handbook on Visual TestingV5N4 2010V5N3Feature Article: Manufacturing ReadinessLevelsTechSolution 17: Toolkit for DoD Manufacturing Engineers3rd Article: Joint Defense Manufacturing Technology PanelV5N4Feature Article: US Army Builds Degradation Resistant BridgesTechSolution 18: Polymer Matrix Composite Manufacturing Induced Defects3rd Article: NDE for the Process Control of PMC FabricationSpecial thanks to Stephanie Knoeller for her excellent work as the primary Editor on this issue.In Memoriam: Sadly, David J. Brumbaugh, a long time AMMTIAC staff member and friend passed away in April. His professionalcontributions were many, his knowledge expansive, and his friendship irreplaceable. He is missed by all of us here and many in thelarger DoD community.Editor-in-ChiefBenjamin D. CraigPublication DesignCynthia LongCopy EditorPerry OnderdonkInformation ProcessingCaron DibertInquiry ServicesOwen R. ConniffProduct SalesGina NashThe AMMTIAC Quarterly is published by the Advanced Materials, Manufacturing, and Testing InformationAnalysis Center (AMMTIAC). AMMTIAC is a DoD-sponsored Information Analysis Center, administrativelymanaged by the Defense Technical Information Center (DTIC). Policy oversight is provided by the Office of theSecretary of Defense, Director of Defense Research and Engineering (DDR&E). The AMMTIAC Quarterly isdistributed to more than 18,000 materials, manufacturing, and testing professionals around the world.Inquiries about AMMTIAC capabilities, products, and services may be addressed to:Micheal J. MorganDirector, AMMTIACP H O N E : 937.431.9322 x103E M A I L : a m m t i a c @ a l i o n s c i e n c e . c o mU R L : h t t p : //a m m t i a c . a l i o n s c i e n c e . c o mWe welcome your input! To submit your related articles, photos, notices, or ideas for future issues, please contact:AMMTIACATTN: MR. BENJAMIN D. CRAIG201 Mill StreetRome, New York 13440P H O N E : 315 . 3 3 9 . 713 6F A X : 315 . 3 3 9 . 7107E M A I L : a m m t i a c @ a l i o n s c i e n c e . c o m

Tia H. Benson-TolleGregory A. SchoeppnerAir Force Research LaboratoryWright-Patterson Air Force Base, OHINTRODUCTIONAdvanced materials are foundational to the capabilities of our militaryplatforms and national defense. For decades the developmentand exploitation of materials technologies has enabled the nation’scompetitive advantage in weapon systems. From the air superiorityof the F/A-22 and the strategic capability of the B-2, to situationalawareness and networking provided by our orbiting satellites, toadvanced marine systems and innovative ground systems for today’ssoldiers – all can tie system level performance benefits to the use ofadvanced materials, such as lightweight metals, polymers, ceramics,and composites. Yet today the DoD enterprise that discovers, develops,and transitions materials for exploitation by weapons platformsis at a crossroads.The practices and processes for material qualification and transitionthat have been established by the military and industrial basethrough the 20th century were developed under a very differentenvironment than what is expected for the future. The materialsthat are being developed today and those envisioned for the futurewill not be served by the historic qualification and transitionprocesses of past programs due to the changing defense acquisitionmodel. The defense materials community and associated stakeholdersmust work together to evolve current practices if they are toeffectively exploit new emerging material concepts for nationaldefense initiatives.Recently, experts gathered to discuss and address these challengingmaterials transition issues. This article summarizes thebackground to the changing materials transition paradigm, futurechallenges, stressors on current practices, recommendations forgoing forward, and some best industry practices.CURRENT ACQUISITION ENVIRONMENTThe material transition paradigm that has been used in priordecades with multiple platform development programs and numerousinsertion opportunities is not feasible in the current acquisitionenvironment. The current environment has a relatively low numberof platform acquisition programs and provides limited opportunitiesto gain fielded experience with new materials. Furthermore, thetime it currently takes to field most defense systems is quite longand stifles transition. The current DoD acquisition process is on theorder of a decade, which risks technology obsolescence by the timethe system is fielded.Defense acquisition programs are increasingly trending towardconcurrent development and production, a strategy that involvessignificant risk. One risk mitigation approach is to use materials thathave been utilized on previous platforms to reduce cost and schedule.If this is indeed a trend in the management of risk in weapon systemacquisition, it may be expected that future DoD major acquisitionprograms will favor previously used materials resulting in limitedopportunities to transition new materials. A limited ability to transitionnew materials to new weapon systems will impact not only futuredefense capabilities, but will ultimately have detrimental effects onmaterials research, development, and workforce education. Moreover,PershConferenceThe Persh Conference construct was developed as a new discussion forum for in-depth investigation and discussion toaddress issues of common interest and relevance to the DoD materials and process community. It was initiated by theDefense Science and Technology Reliance 21 Materials and Processes Panel in recognition that direct communicationbetween the diverse stakeholders in defense materials through a constructed format can provide rapid assessments ofevolving issues that this community faces that does not exist in traditional forums. To encourage open and rapidexchange on the diverse and timely ideas and stimulate a broader discussion on key issues, strategic investment, andpolicy options, Persh Conferences are by invitation only with no published proceedings. Diverse stakeholders arebrought together around a single topic, with perspectives ranging from technology to policy and from research to application.The format of the conferences is very interactive and is composed of talks to provide context and interactivepanel discussions to explore and probe issues and opportunities. The results of each Persh Conference are analyzed, andassessments and recommendations developed and submitted to the DoD and shared with the participants. The forumis unique in that it provides a holistic look at a topical subject in a national security context and enables identificationof where the materials and processes community should focus its efforts and energy in research and otherwise.The Defense Science and Technology Reliance 21 Community of Interest provides materials technologies, processesand related research and technology products as well as the scientific and engineering expertise needed to maintainand enhance US defense capability. Its goals are to strengthen science and technology planning by improving integrationof investments with a DoD-wide strategic view and enhancing coordination between the science and technologycommunities within DoD.The AMMTIAC Quarterly, Volume 6, Number 1 3 http://ammtiac.alionscience.com

it could potentially cause the advancement of certain classes of materialsto become stagnant.CHALLENGES THAT IMPEDE MATERIALS TRANSITIONSeveral challenges may prevent the exploitation of high performancematerials to create weapon capabilities across various platforms.There is a large body of anecdotal evidence and consensus withinthe materials research and development communities that demonstrateshow the current methods of transitioning materials are lessthan desirable. Convening experts from various stakeholdersthrough the Reliance 21 meetings and the Persh Conference (seesidebar) has led to the identification of many of the barriers to materialstransition. Some of these challenges are discussed in the followingparagraphs.Scaling of MaterialsOne challenge occurs when scale-up effects from simple materialproperty testing coupons to larger panels or components are notwell understood. For example, early material performance of anadvanced metallic alloy for a particular application was measuredfrom simple coupon samples. These tests showed that the materialmet all of the targeted requirements for the application, whichresulted in additional testing and investment in the material. Oncethe material processing and manufacturing were scaled up to largerpanels, testing of the larger panels revealed that the material nolonger met the performance requirements. Failure of the material tomeet requirements at the larger scale was due to residual stresses thatwere insignificant and went largely unnoticed in the initial couponspecimens but were significant in the larger panels. A common reasonfor material transition failure is not necessarily insufficientcoupon data, but failure to properly account for scale-up in themanufacturing processes.Point De signMaterials qualification for cross-platform use typically focuses on asingle type of application. For instance, the suitability of a materialfor use in airframe structures is tested in a limited range of environmentsand has different qualification tests than for an aircraft engineapplication. Under past and current practices the average number ofqualification tests for a single application range from 1000 to 3000specimens and requires from 1 to 3 years for completion. To qualifya material for multiple types of applications becomes increasinglydifficult and costly. The research and development community doesnot typically have the resources to mature technology to the pointthat the material can be qualified and transitioned to a program.A result of the push for more rapid transition has been the strategyto qualify materials to a point design – that is, the testing is limitedto only address a specific component design, set of loads, andenvironment. This practice reduces the time and cost of inserting amaterial. However, materials qualified to a point design are notreadily translatable to other applications because the reduced testingeliminates the possibility of direct transition to other applications.Weapon System Life and Materials AvailabilityThe requirements creep seen over a weapon system’s life representsa challenge to materials qualification and is unique to the defensecommunity. Many weapon systems have service lives spanning severaldecades that can include multiple service life extension efforts.After a material is successfully transitioned to a major platform, longservice lives often necessitate repair or removal and replacement ofaging or damaged materials and components. Material obsolescencethat may involve changes to constituents, environmental lawchanges necessitating a change to the material or how it is processedand second source qualifications are among the reasons for materialsto undergo costly re-qualification numerous times throughoutthe life of the platform.Alignment of Material Developer and Material IntegratorRequirementsThe alignment of the material maturation timeline with the materialselection phase of the acquisition timeline is a major factor in successfulmaterial transition. Case studies have shown that materials can besuccessfully qualified when the material developer has early visibilityinto well defined material requirements and needs, the product is welldeveloped for the application, and the material development andqualification are fully resourced with a strong customer pull. Materialdevelopment and qualification are slow or unsuccessful when therequirements are poorly articulated, there is a late definition or changein requirements, or there is a lack of a clear value proposition. Late orpoor definition requirements can lead to incapable material for theapplication that can significantly slow or impede qualification andultimately jeopardize program execution. The current lack of synchronizationbetween material development and application opportunitiesmay become a greater challenge as DoD weapon development cyclesadapt to the current highly-dynamic threat space and finds needs fordiverse, tailored and low production-number weapons. The materialsupplier must have a clear understanding of the customer’s qualificationtesting requirements that may be application specific and differentfor each customer. Finally, qualification efforts can be hamperedby second-source qualification efforts as well as changes in requirements,in needs or in schedule.Risk Reduction MethodsCurrent empirical qualification approaches are widely seen as costlyand time consuming, and some consider them antiquated processesthat penalizes materials insertion. Although improvements to thequalification process are seen as long overdue and much needed, itis the responsibility of the certification community to manage risk,and any alternative approaches to statistically-based materials databaseswill be required to be risk neutral.Five factors (prerequisites) responsible for reducing the risk fortransition (see sidebar) have been identified for successful applicationof advanced structural material systems (see Figure 1). Theprerequisites for successful transition are: stabilized materials andI. StabilizedMaterialsandProcessesAccept/ FacilityProcess reject assessmentscale-up criteriaProcessdevelopmentMaterialscreeningFive Factors for Technology TransitionII. Producibility: Manufacturing Scale-UpMaterialdevelopmentStructuralIntegrity• Repairability• Maintainability• ReliabilityManufacturingmethodsdevelopment• Analysis• StructuraltestingEvaluation ofproduvibilityAllowables• Element• SubcomponentCannot just focushere; have to lookat the entire pictureIII. CharacterizedMechanicalProperties(start of EMD)V. SupportabilityIV. Predictability ofStructural PerformanceFigure 1. Factors in Past Successful Structural Materials TransitionThe AMMTIAC Quarterly, Volume 6, Number 1 4 http://ammtiac.alionscience.com

processes, demonstrated producibility and mature supply chain,characterized mechanical properties, predictability of structural performance,and demonstrated supportability including repairability.These factors, as desirable as they are, may not be achievable forfuture materials applications due to cost or time constraints in thesame manner as they have been in the past.When system and platform manufacturers are in competition formajor defense acquisition programs, they are willing to consider theinsertion of higher risk technologies for competitive performanceand cost advantages. However, after program award, manufacturerstypically become more risk averse and technologies used in theTechnology Development phase that have not sufficiently maturedor are determined to be too high risk may not make it into theEngineering & Manufacturing Develop phase of the program.Knowledge and Experience BaseThere is a strong sense that the community needs to better capturethe materials development, qualification and transition experience ofall stakeholders, down to the experiences of individual people.Today’s practice of transferring experienceand knowledge often relies onnon-formal collegial or mentor-toapprenticerelationships that may bead hoc and non-archival in nature.Today there exists no formal nationalfocus on providing education in criticaltopics such as materials design (versusa materials selection process) andin computational tool integrationacross disciplines. Such training wouldprovide for a more robust knowledgetransfer. Anecdotal evidence suggeststhat several elements are critical for successful transition of materials:people and their education, transfer of knowledge, trust and comfortwith new materials and processes, and the ability to communicate.Computational ToolsA common theme identified by researchers, material suppliers, systemsintegrators, and acquisition and warfighter stakeholders is the need toshorten the time for the materials development cycle without increasingthe risk associated with inserting a new material. Material testinghas been identified as one aspect of the materials development cyclethat can potentially reduce development time and cost. However, thereis recognition that the certification community has historically managedrisk in part through the empirical, statistically-based materialallowables process. Therefore, processes to reduce testing requirementsthat employ critical strategic testing with predictive models must be• Early involvement of acquisition program essential• Small program window for transition opportunityTiming• Need acceptable TRL& MRL at need date• Less mature technologyis higher risk, notlikely to be on criticalprogram pathEarly Requirements DefinitionTechnology MaturationRiskFigure 2. Technology Transition – Managing Risk, Payoff,and TimingPerformance/Cost ROIPayoff• Potential acceptanceof higher risk withhigh payoff revolutionarytechnologies• Risk aversion to lowpayoff evolutionarytechnologiesdeveloped, matured and validated to provide a level of confidence atleast as good as the existing empirically-based processes. Currently, thelack of high fidelity and high confidence predictive models is a significantbarrier to implementing these processes.Stakeholders have identified the growing need to bringenhanced computational capabilities into the materials developmentcycle. Utilization of computational methods is sought notonly to guide and reduce the material testing needed to fully characterizematerial performance, but also to help guide the design ofnew materials. Additionally, material suppliers can potentially usematured computational tools for initial material screening and thedevelopment of a business case early in the material developmentcycle for a given material’s application. Articulation of the returnon investment (ROI) or business case for using a material is criticalfor material trade studies in the early phase of DoD acquisitionprograms. Some of the current challenges hampering the expandeduse of computational tools are computer code run times, lack ofintegration of various tools and codes, and the fact that the use ofcommercial codes typically requires specialized expertise and training.Microstructure models andprocess modeling require specializedknowledge. Challenges hamperingexpanded use of computational toolsin materials development and transitionalso reside in current curricula,which do not yet broadlyemphasize computational tools inmaterials science and engineering.EMERGING TRENDS AND BESTPRACTICESSome successful practices in facilitatingthe transition of new materials from many perspectives rangingfrom material suppliers to systems integrators have been collectedand articulated by those with recent experience in the process. Manyfactors have been identified across stakeholders as critical to rapidqualification. These include communication amongst all stakeholders,early visibility into system requirements for the material supplier,well developed testing protocols, understanding of design driversby all parties, and OEM teaming with material developers andsuppliers. Early involvement of the acquisition program office isessential as risk management, not technology insertion, is paramountto a major acquisition program. A material’s capabilitiesmust link to requirements and it has been shown that technologypull has been more effective than technology push in getting newmaterials onto DoD platforms. Identification of the application firstto guide material development is often more successful than tryingRisk as a Factorin TransitionWhen deciding what technologies to insert into weapon systems and platforms, technology integrators must weighthe interdependence of timing (technology maturity level), payoff (ROI), and risk. For today’s DoD acquisitionprograms, most new materials must be considered in the Materiel Solution Design Phase prior to Milestone A orthey are viewed as being too late to impact a program. However introducing a new material into a program beforeit is at an acceptable technology readiness level (TRL) and manufacturing readiness level (MRL) makes it difficultto assess the business case and ROI making it high risk. New materials are viewed as having lower ROIs than is initiallyprojected early on in their development phase because selection decisions must be made early when qualityinformation is limited. Less mature technology is higher risk to the program and is not likely to be on a criticalprogram path unless there is a compelling high payoff in performance or ROI. There is a potential for acceptinghigher risk for enabling revolutionary materials, but there is risk aversion to new evolutionary materials that are lowpayoff in terms of cost and performance. Figure 2 summarizes some of the interactions of timing, payoff and risk.The AMMTIAC Quarterly, Volume 6, Number 1 5 http://ammtiac.alionscience.com

to find a home for a newly developed material.Collaborative relationships between material suppliers and theintegrators have been a key to addressing causes for the slow adoptionof new materials. Some successful practices include establishinga roadmap working group to coordinate materials development andstructures development roadmaps. These provide early visibility intorequirements and early identification of technology need dates forplanning the material and supply chain maturation. Such a relationshipserves to develop a collaborative testing approach for standardmethods and minimizes testing issues. When materials suppliershave a clear understanding of the customer’s material and testingrequirements, there is a greater chance that the material will ultimatelymeet the customer’s needs. Beyond specific platform materialdevelopment, the integrator must inform the material suppliercommunity of future material needs well in advance to ensure thatthe supply base is actively working on technologies to meet theneeds of the next-generation platforms.The aforementioned best practices have been used over the pastdecade within the DoD materials community. However, in light ofthe changing nature of the DD landscape and its loss of stature asbeing the nation’s driver for material technology, innovation may befound by working with non-traditional, forward leaning companiesfor materials development and transition. Best practices from othersectors and markets such as automotive and pharmaceuticals onapproaches for technology transition may offer useful insights intoprocesses that can be exploited to improve DoD technology transition.New materials such as nanocomposites are being successfullytransitioned into some markets, and emerging materials such asactive materials are being developed and considered within severalindustries. Several factors that enhance successful implementationacross these other market sectors have been identified. These includedclose communication between all parties involved in productdevelopment, the use of processes for prioritizations and review ofprogress, and recognition of the role of identifying and nurturingnew technologies to remain competitive. Within for-profit companies,it is critically important to transition new technology into marketableproducts to retain a competitive advantage.Innovative processes and methodical approaches are often used inindustry to focus research, and quickly mature promising research. Yetit is acknowledged that such approaches can both enable and hindermaterials development and transition. Business managers value theseapproaches since they allow for the assignment of a value to R&D andthe tracking of R&D, but some assert that innovation suffers undersuch systems. In some cases, research is only funded if it can be identifiedhow the technology will be utilized in a product. Some factorsthat influence the business case include the timing of the technologyinvestment, the development and insertion cost, the availability andquality of the material, and the supplier’s knowledge of the integrator’sneeds. Definition and articulation of the business case for thedevelopment of new materials is important and in some cases there isa reluctance to be first to use a technology knowing that once a precedenthas been established to use the technology, it is easier to integrateinto a product. Some companies choose to rely upon external collaborationsfor basic research rather than performing it themselves.Research and development are more likely to be successful if multi -disciplinary product teams are established early in the design cycle toguide product development. Today many are increasingly recognizingthe importance of learning from other market activities, research, andneeds. In addition, there is a growing awareness of the necessity toleverage across communities, recognizing that innovation comes frommultiple sources, and not just from internal resources. A cultural shiftaway from the mentality of ‘not invented here’ and a reliance on leverageappear to be emerging and increasingly valued.A PATH FORWARDSeveral recommendations for improving material transition resultedfrom the Persh conference. These are explained in the followingparagraphs.It is recommended that the Defense Science Board and otherappropriate organizations are engaged to study various approachesto qualifying materials for diverse markets and recommend an alternativemethod for the DoD of the future. Specifically, variousindustries should be assessed to identify best practices. Previousmaterial qualification processes should be built upon and updatedbased on current geo-political, economic, defense, and technologyfactors. The need and role of government supported initiativesshould be addressed to facilitate a seamless technology transformationfrom inception to implementation. For instance, these couldinclude initiatives that promote more integrated collaborationbetween systems manufactures and material suppliers (e.g., todemonstrate breakthrough improvements as a result of having suppliersfully engaged from the onset), or initiatives that are open tonew innovations, including rule and process changes to exploitadvanced concepts to the fullest extent. Finally, the Defense ScienceBoard or Institute for Defense Analysis should be engaged to performa study and recommend the optimum role of governmentS&T in shaping future qualification/certification processes.Another recommendation is to establish an OSD 6.3 ProgramElement that addresses scale up and transition of materials technology.The appropriate funding level would need to be determined. OSDshould also be chartered to perform an industrial base assessment todetermine how to best posture industry to rapidly exploit and transitionnew materials and processes for improved weapons capabilities.Recommendations of how to better incorporate materials knowledge,including modeling, into the education system should bedeveloped by bringing together various entities, such as the NationalMaterials and Manufacturing Board (NMMB) of the NationalAcademies; government science, technology, engineering, and math(STEM) education groups; and a round table of material-centrictechnical societies (such as MRS, SAMPE, and ASM). This shouldfocus on future-leaning needs such as the incorporation of probabilisticconcepts, computational methods, and materials design (asopposed to materials selection). Furthermore, the DoD should evaluateforums that can be used to actively integrate all stakeholders formore efficient communication and to build on best practices.Finally, a DoD-centric computational materials study should beperformed with an objective look at roles and payoffs of computationalmaterials science and engineering (CMSE) and integratedcomputational materials engineering (ICME) in the developmentand transition of materials in today’s geo-political and economiclandscape for defense applications. Several general CMSE studieshave been performed in the past, and therefore this should benchmarktools circa 2011 and look to define capabilities that canimpact materials transition today as well as foundational researchrequired for envisioned future needs.To comment on this article, email: ammtiac@alionscience.comThe AMMTIAC Quarterly, Volume 6, Number 1 6 http://ammtiac.alionscience.com

techsolutions 19Joseph A. ReedBrady McNaughtonArchitectural Testing, Inc.York, PABlast Resistant Fenestration Design & TestingINTRODUCTIONBlast resistance remains a top priority for high-risk government,defense, and financial buildings. Windows, doors, and skylightsare, in most instances, the points of vulnerability when consideringa structure’s ability to withstand explosive forces and protect itsoccupants. It is critical that these components be designed to theappropriate standard and thoroughly tested to validate their infieldperformance. In fact, many government agencies, privatebuilding owners, consultants, and engineering firms mandate thattheir building components be tested and subsequently rated basedupon their ability to mitigate the effects of blast events as well asthreats from ballistic and forced entry attack. This article summarizesthe characteristics and effects of blast waves, and discusses thehardware, software, and methodology that allows their simulationwithin a test environment.BACKGROUNDDuring any blast-type event, building occupants can be injured orkilled by: direct exposure to blast loadings (pressure or shock waves),the impact of fragments and debris, impact with surroundings wheneither a structural element or the person is impelled by the blastwave, or structural collapse.Of these, limiting the impact of debris is particularly importantin the case of fenestration (windows, doors, and skylights).Statistics show that approximately 80 percent of the injuries resultingfrom blast events are caused by airborne shards of glass frombroken windows. These glass shards can fly inward at speeds greaterthan 200 feet per second (136 mph).Blast CharacteristicsWhen an explosion occurs, there is a near instantaneous heating andsubsequent expansion of the surrounding air, which results in theformation of a shock wave. The shock wave travels away from thesource in a radial fashion at supersonic speeds, while also decreasingrapidly in magnitude. This decrease in magnitude is modeled usingthe inverse cube of the distance from the explosion site.The archetypal blast waveform features a positive phase that ischaracterized by a virtually instantaneous rise to the peak overpressureand rapid exponential decay until it reaches a value of zero. Atthis point, air backfills the vacuum that is created as the blast wavepasses. This is termed the negative pressure phase.The peak pressure of the blast, which is dependent on the chargeweight, and the time over which the initial pressure wave decays to zerotogether define the impulse energy delivered. While peak pressure isapplied instantaneously, the delivered energy or impulse is cumulative.For most architectural design purposes, the blast impulse orblast loading waveform may be simplified and assumed to be of atriangular shape with the peak overpressure decaying linearly toambient pressure in a time known as the positive phase duration.In this case, the impulse is simply the area of a triangle as shown inFigure 1. The impulse is calculated using Equation 1, where I is theimpulse in (psi-ms), P is the peak pressure (psi), and t d is the durationtime in (ms).I = (½) t d • P Equation 1A more precise characterization may be obtained using a softwarepackage that implements the standard Kingery-Bulmash air blastequations used in most Department of Defense (DoD) technicalmanuals. Alternatively, tables of pre-determined shock parametersmay be used to estimate blast pressure and impulse.When a shock wave encounters a structure, it may be reflected.The reflection causes a pressure load on the structure that also hasa peak pressure and impulse. In general, the reflection is a functionof the angle of incidence. For the portions of the structure that areperpendicular to the shock wave propagation (zero angle of incidence),the reflected pressure is maximum and greater than thatof the original shock wave. For portions of the structure that areparallel to the shock wave propagation (90° angle of incidence),the reflected pressure is approximately equal to the free field pressureof the explosion. As the shock wave traverses, highly dampedpressure oscillations occur as the pressure returns to its ambientvalue. This results in a negative phase pressure in both the free fieldand reflected pressures. It is the reflected pressure and impulse thatthe designer must consider when evaluating a structure or itsfenestration. Figure 2 illustrates the interaction between a shockwave and a building.Since a shock wave is characterized by both magnitude and time, itis a dynamic load. Accordingly, the fenestration element will have adynamic response which is dependent on both the strength and stiffnessof the product. Common fenestration materials have differentphysical and mechanical properties; thus, their dynamic response canbe substantially different between two shock waves of identical peakPressure (psi)(+ psi)AmbientAtmosphericPressure(- psi)Typical Blast WaveIncident (Side-on) OverpressurePeak Overpressure (P)Measured in psiImpulse (I )Measured in psi•msPositive PhaseDuration (t d )Time (ms)Negative PhaseDurationFigure 1. Blast wave diagram (courtesy of AmericanArchitectural Manufacturers Association (AAMA))The AMMTIAC Quarterly, Volume 6, Number 1 7 http://ammtiac.alionscience.com

techsolutions 19AMMTIACA D V A N C E D M A T E R I A L S , M A N U F A C T U R I N G A N D T E S T I N GPPrI = (1/2)Pr•t dstrength. Estimating a total system response by aggregating theseindividual analyses often results in a very conservative design.Physical testing of the complete assembly to the actual design loadsprovides a more realistic validation of the assembly.P oINITIALEVENTFREE-FIELDDECAYt dNEGATIVE PHASEPerformance StandardsTo ensure that components are manufactured and buildings aredesigned to meet the challenges of blast resistance, standards havebeen developed. The two most widely used glazing performancestandards and hazard-classification schemes are published by theGeneral Services Administration (GSA) and the DoD.t oREFLECTEDPRESSURE, PrFigure 2. Shock wave interaction with a building.pressure, but different impulses. If the period of the shock wave isclosely matched to the natural period of the component, there may bean amplification of the component response analogous to resonance.Therefore, it is important to evaluate the product at precisely the specifiedshock wave conditions and for the exact construction intendedfor the project.DESIGNING BLAST RESISTANT FENESTRATIONTo mitigate the hazards posed by flying glass fragments, windowsystem designs should be balanced, meaning that the glazing*,frames, and anchorage are able to survive a blast loading. In general,if one part of the system fails, the entire system will fail. Similarly, ifthe system has a higher capacity than the supporting wall, when thewall fails the entire window system may be blown into the facility.The basic criteria for the design of blast-resistant or blast mitigatingfenestration systems are that the glass should remain intact andin the frame, broken but not blown out; the frame must stayattached to the wall; and the wall must remain intact to hold theframe. Protective glazing measures would also be appropriate forbuildings that are located near high risk targets, even though thebuildings themselves are not considered a target.To predict the behavior of glass under a blast load damagemodels should be developed for windows, and the glazing hazardlevels determined. These models can be used to predict the outcomeof various blast loads. Engineers prepare these models usingsoftware such as WinGard † , Winlac ‡ , and HazL § , developed byUS Government agencies. The developed damage models are in theform of resistance-deflection functions, describing how glassdeflects and breaks under pressure and how the glass shards areprojected once released from the windows. Pressure-impulse (P-I)diagrams, derived from the resistance-deflection functions, help torapidly analyze windows under a range of loads.Once the damage functions are set, the applied blast load for eachwindow is plotted on the P-I diagram and the resulting damage levelis recorded. A graphic of the damage levels for existing windowshelps to visualize the high hazard areas, and the potential for personnelinjury. Such analyses, however, are typically done on a componentbasis only and to different design methodologies. That is, theglazing is analyzed for fragmentation potential with simplifiedtheoretical boundary conditions; frame members are analyzed fordeflection and stress without considering the structural integrity ofthe glazing; and connections and anchors are analyzed for ultimateGeneral Services AdministrationThe GSA first published its Security Criteria, which includes criteriafor mitigating risk from window glass fragments, in 1997. TheInteragency Security Committee (ISC) later adapted these criteriafor at-risk facilities of all federal agencies, except those under DoDjurisdiction. The GSA also developed GSA-TS01-2003, StandardTest Method for Glazing and Glazing Systems Subject to DynamicOverpressure Loadings to provide guidelines for testing using actualexplosive charges or simulated blasts.The GSA documents define five performance conditions thatindicate whether and how far glass shards penetrate into a roomwhen the window and wall segment are subjected to a blast of specifiedpeak pressure and impulse. The performance conditions arenumerically defined on a scale from 1 (“safe” – the glass does notbreak and there is no visible damage to the glazing or frame) through5 (“low” – the glass fails catastrophically, projecting fragments morethan 10 feet from the window to impact a vertical surface [wall ortest “witness panel”] more than two feet above the floor).Department of DefenseIn parallel with the GSA/ISC efforts, the DoD has developed standardsof its own known as Unified Facilities Criteria (UFC). Themost applicable is UFC 4-010-01, entitled Minimum AntiterrorismStandards for Buildings. More stringent than those required by theGSA/ISC Security Criteria, this criteria defines its own levels ofprotection or hazard ratings and, in the architectural category,includes minimum requirements for windows, skylights, and doorsin new and retrofitted buildings.UFC 4-010-01 defines five Levels of Protection based on likelihoodand degree of building collapse and personnel injury due toflying glass fragments. These levels of protection are establishedonce the standoff distance is determined and are similar to, butdescribed differently from the performance conditions and protectionlevels cited in the GSA standard. The levels of protection aresummarized in Table 2.1, page 2-7 of UFC 4-010-01.To minimize the hazards caused by flying glass fragments, UFC 4-010-01 prescribes specific provisions for new and replacement glazingand window frames, noting that “window and door designs must treatglazing, frames, connections, and the structural components to whichthey are attached as an integrated system.”PERFORMANCE CERTIFICATION AND TESTINGUFC 4-010-01 states that it is acceptable to dynamically test windowand skylight systems to determine their performance as equivalent toor better than their applicable hazard rating. This may be done as analternative to the prescriptive provisions of the standard. Such testingincludes the entire window or skylight system and connections, andis conducted in accordance with ASTM F 1642 -04, Standard TestThe AMMTIAC Quarterly, Volume 6, Number 1 8 http://ammtiac.alionscience.com

techsolutions 19AMMTIACA D V A N C E D M A T E R I A L S , M A N U F A C T U R I N G A N D T E S T I N GTable 1. Arena test advantages and disadvantages.AdvantagesDisadvantages• Most accurately reproduces the blast waveform • High cost• Several products can be tested simultaneously • Area required must be quite large with long standoff distances, and be isolated from the public• Few specimen size limitations• Requires multiple test chambers (witness rooms) and instrumentation if multiple tests areconducted with one blast• Long set-up time for initial and repeat test runs• Subject to weather variationsSOD 100 ft (30 m)SOD 50 ft (15 m)Figure 3. Arena test set-up. Diagram courtesy of AmericanArchitectural Manufacturers Association.Method for Glazing and Window Systems Subject to Airblast Loadings.Testing reveals problems such as inadequate fasteners, excessiveframe deflection, or brittle failure. Testing and the subsequentanalysis is a useful tool for designers, architects, consultants, andmanufacturers since it aids in the development of improved productsthat better mitigate the glass fragmentation hazards.To conduct the tests necessary to qualify a fenestration system, afully glazed and assembled mock-up must be prepared usingapproved shop drawings. Since the method of installation for ablast mitigating product is as important as the product itself, itmust also be evaluated during the testing. Therefore, the mock-upmust accurately represent the project in every detail, includingglazing, hardware, operation, installation and the type, number,arrangement, and orientation of the anchoring fasteners. Tests maybe conducted in an open air arena with live explosives or using ashock tube.Arena TestThe arena test is an open-air test in which a test subject is installedin a support structure and exposed to an actual explosion. For arenatests, the characteristics of the blast wave (peak pressure andimpulse) are determined from handbooks or with computer software.These characteristics are then used to select an appropriateexplosive weight based upon the available standoff distance (SOD)at the arena test facility. Figure 3 shows an example test set-up. Theadvantages and disadvantages of the arena test are summarized inTable 1.Shock Tube TestThe shock tube test uses a pressure vessel charged by air or nitrogento test a sample. The key components are illustrated in Figure 4.The driver is a pressure vessel with an adjustable volume that isclosed by membranes in the initiator flange. When the membranesburst, the rapid release of pressure creates a shock wave that is tunedby the expansion duct, cone, and shells to replicate the reflectedpressure profile generated by the specimen.For a particular charge weight and standoff, the characteristics ofthe blast wave (peak pressure and impulse) are determined fromthe same handbooks or computer software used in arena testing.The test engineer uses the parameters to set the shock tube drivervolume, driver pressure, and shell configurations such that theyreplicate the blast wave. Shock tube configurations for various peakpressures and impulses are established by developing performancecurves when the shock tube is commissioned. The advantages anddisadvantages of the shock tube test are presented in Table 2.Some shock tubes have data capture capabilities that includehigh-speed, high-resolution color digital video up to 5,000 framesper second and data collection rates up to 10,000,000 samples perchannel per second. If equipped with a reusable test frame, fast testset-up and repeat testing are enabled. In addition, tests can be rerunwith varied parameters simply “dialed in,” allowing repeatedtesting of specimens in rapid succession, typically ten tests per day,under a spectrum of conditions. Thus, shock tubes are well suitedfor balanced design validation by progressively increasing load onone window to establish glass break before frame failure.Once the tests are completed, post-blast engineering analysis ofblast parameters and shatter patterns determines the level of blastprotection rating provided by a product.DriverExpansion DuctShellsWitness ChamberInitiator FlangeFigure 4. The key elements of a shock tube.ConeSpecimen FrameThe AMMTIAC Quarterly, Volume 6, Number 1 9 http://ammtiac.alionscience.com

techsolutions 19AMMTIACA D V A N C E D M A T E R I A L S , M A N U F A C T U R I N G A N D T E S T I N GTable 2. Shock tube test advantages and disadvantages.Advantages Disadvantages• Lower cost when compared to the • Limitations on peak pressurearena test• Indoor environment permits control • Limitations on specimen sizeand reproducibility of test conditions• No weather delays• Rapid “test-adjust-retest” capabilityassists design efforts• Unique test parameters can beeasily dialed inBLAST CERTIFICATIONOnce the test results and analyses are completed, blast-resistant fenestrationproducts may be third-party certified by programs thatinclude laboratory testing, validation of the manufacturer’s qualityassurance program, and plant inspections.Certification can take either a “product-specific" path by testingat an ISO 17025-accredited laboratory according to UFC,GSA or other accepted performance standards, or a “project specific"path by testing to confirm compliance with individualproject specifications and approved shop drawings. Either pathrequires continued, demonstrated compliance with ICC-ES AC10quality control documentation requirements at the manufacturingplant and verification. Each certified product and actual installationmust comply with the referenced standards, as confirmedduring periodic on-site audits of manufacturing plants and installationsites.CONCLUSIONWhile comprehensive protection against the range of possiblethreats may be cost prohibitive, an appropriate level of protectionintended to lessen the risk of mass casualties resulting from blasttypeevents can be provided for all personnel at a reasonable cost.Testing and rating of the ability of blast-resistant fenestration productsto meet current standards, while not a guarantee of absolute safety,is the best way to maximize protection while optimizing buildingenclosure design to meet all building and site functional requirements.In general, the lower cost and fast turnaround of shock tubetesting is likely to result in more products being tested and verifiedfor blast-resistant performance than if arena testing alone is used.NOTES* Window glazing is the glass portion of the window assembly.† Window Glazing Analysis Response Design. This software was the first available forthe prediction of glass hazards and has become a national standard used by manyagencies. A state-of-the-art method to analyze and predict the behavior of windowglass under blast loads, this program calculates and graphically displays the responseof window systems subjected to blast loads. WinGARD is available for download atwww.oca.gsa.gov.‡ Window Lite Analysis Code. Versions 4.0 and later are derivative versions of theWinGARD GSA code adapted to meet the unique requirements of the USDepartment of State.§ Window Fragment Hazard Level Analysis. This program calculates the glazingresponse to a blast loading and provides a debris transport model for predicting fragmenttrajectory. It allows modeling of monolithic glass or plastic windows, laminatedwindows, insulated glass units and windows retrofitted with anti-shatter film.HazL is available for download from https://pdc.usace.army.mil/software/hazl/.GENERAL REFERENCESStandards and Test MethodsUnited States General Services Administration, “Standard Test Method for Glazingand Glazing Systems Subject to Dynamic Overpressure Loadings,” GSA TS01-2003,1 January 2003, http://www.gsa.gov/graphics/pbs/Standards_GSATestingStandard.pdf, accessed 20 January 2011.United States Department of Defense, “Unified Facilities Criteria (UFC): DoDMinimum Antiterrorism Standards for Buildings,” UFC 4-010-01, January 22,2007, http://www.protectiveglazing.org/resources/UFC4-0100122%20Jan%202007.pdf, accessed 20 January 2011.United States Department of Defense, “Unified Facilities Criteria (UFC): DoDMinimum Antiterrorism Standoff Distances for Buildings (FOUO),” UFC 4-010-02, 19 January 2007.Headquarters, Department of the Army, “Physical Security,” Field Manual FM 3-19.30, 8 January 2001.United States Department of Defense, “Unified Facilities Criteria (UFC): GeneralBuilding Requirements,” UFC 1-200-01, 16 August 2010.American Architectural Manufacturers Association, “Voluntary Guide Specificationfor Blast Hazard Mitigation for Fenestration Systems,” AAMA 510-06, 2006.ASTM International, “Standard Practice for Determining Load Resistance of Glassin Buildings,” ASTM E1300-04e1.ASTM International, “Standard Test Method for Glazing and Glazing SystemsSubject to Airblast Loadings,” ASTM F1642-04, 2010.ASTM International, “Standard Practice for Specifying an Equivalent 3-SecondDuration Design Loading for Blast Resistant Glazing Fabricated with LaminatedGlass,” ASTM F2248-03.International Council Code – Evaluation Service, “Acceptance Criteria for QualityDocumentation,” ICC ES-AC10, www.icc-es.org.International Organization for Standardization, “Glass in Building – Explosion-Resistant Security Glazing – Test and Classification for Arena Air-Blast Loading,”ISO 16933, 2007.International Organization for Standardization, “Glass in Building – Explosion-Resistant Security Glazing – Test and Classification by Shock-Tube Loading,”ISO16934, 2007.Published ArticlesRemennikov, A.M., “A Review of Methods for Predicting Bomb Blast Effects onBuildings,” 2003, http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1360&context=engpapers, accessed 21 January 2011.Swisdak, M.M., Jr., “Simplified Kingery Airblast Calculations,” Indian HeadDivision/Naval Surface Warfare Center, August 1994, http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA526744&Location=U2&doc=GetTRDoc.pdf,accessed January 21, 2011.Joseph A. Reed, PE, is Director for Engineering and Product Testing at ATI. Mr. Reed holds a Master of Science in Civil Engineering from Lehigh Universityand is the inventor or co-inventor on 14 international patents. He has active engineering experience since 1988 and joined Architectural Testing, Inc. in 2002,where he is now responsible for structural analysis of building envelope components and cladding constructions relating to building code compliance and projectrequirements. He guides the preparation of test routines and analyzes results for wind and blast load performance of window, storefront and curtainwall installationsdesigns and conducts structural analysis of fenestration assemblies and components.Brady W. McNaughton, P.E., Manager of the Security Research Center, has been involved in security related testing and engineering since he joined theArchitectural Testing team in 2006. He oversees all blast, ballistic resistance, forced entry resistance and fire testing performed in the Security Research Center.Brady is a member of several professional organizations and currently has Professional Engineering licenses in two states.The AMMTIAC Quarterly, Volume 6, Number 1 10 http://ammtiac.alionscience.com

Edward W. TokarskyMark L. RobinDuPont Co., Chemicals and Fluoroproducts BusinessWilmington, DelawareINTRODUCTIONHalon fire extinguishants are clean, meaning that they can suppressfires without causing additional damage as a result of their use.Although halon is an excellent extinguishant its production hasbeen banned for most applications due to its contributions to ozonedepletion. For decades, researchers have been working to develop anequally well performing replacement with limited success. Thispaper reviews the development of halon, its characteristics, the alternativesthat have been developed, and the reasons that these alternativesare inadequate.HISTORICAL BACKGROUNDThe history of fire extinguishants goes back in antiquity to atleast the time when a caveman lost control of a bonfire whileroasting his most recent hunting success. Water was likely thefirst extinguishant. It worked well and no one was particularlyconcerned about the mess created in dousing the fire. Water continuedas the principleextinguishant into moderntimes, being usedextensively in well knownhistorical events such asthe Great Chicago Fire of1871. The focus wasplaced on putting out thefire as quickly as possibleto save lives; extinguishantdamage was accepted as a necessary evil.Water and dry chemical based systems (e.g., bicarbonates) havecontinued to evolve into highly engineered and effective 21st centuryoptions, but still can create significant damage in the course ofapplication. In addition to facility or equipment replacement costs,downtime and critical continuity-of-use considerations often havevery high value, especially in modern DoD systems.HALON DEVELOPMENTThrough the early and mid-20th century, questions were raised asto whether it was possible to suppress fires without creatingimmense damage during the extinguishing process. Extinguishingagents such as carbon tetrachloride (CCl 4 ), bromomethane(CH 3 Br), and bromochloromethane (CH 2 BrCl) were developedin the early 1900s and found to provide the desired clean extinguishmentcharacteristics. Although widely employed in militaryIn the halon nomenclature, thefirst digit represents the numberof carbon atoms in the molecule,the second the number of fluorineatoms, the third chlorine, fourthbromine, and the last iodine.and civilian applications during this period, these agents werefound to be highly toxic.As expensive, complex, and mission critical electrical devicesentered military service, especially during WWII, the need for anextinguishing agent that was both clean and of low toxicity intensified.Consequently, the USArmy funded an extensiveresearch project at PurdueUniversity, beginning inSeptember 1947, to searchfor low toxicity, high efficiency,and clean fire suppression agents.[1] Following an extensiveanalysis of over 65 candidates, Purdue identified a class ofcompounds, now known as halons or HALogenated hydro -carbONS that provided efficient and clean extinguishment, whilealso being low in toxicity. Following additional investigation,halons 1301 (CF 3 Br) and 1211 (CF 2 BrCl) emerged as significantcommercial successes. The relevant physical properties for thesetwo compounds are compared in Table 1.Civilian and military fire suppression systems that used halonswere widely specified and installed into the 1980s. The elevated safepersonnel exposure concentration and gaseous nature of Halon1301 led to its finding principle use in total flooding applicationswhere a specific concentration of extinguishing agent is employedto completely fill (“totally flood”) an enclosure, and provide extin-Table 1. Comparison of Halon 1211 and 1301.Halon 1211 Halon 1301Primary Applications Handheld and Total Flooding SystemsAreaWheeled ExtinguishersChemical Formula CBrClF 2 CBrF 3Molecular Weight 165.4 148.9Boiling point, °C -3.4 -57.7Extinguishing Concentration, 4.1 3.5% in air for heptaneCardiac sensitization 0.5 5NOAEL*, % in airCardiac sensitization 1 7.5LOAEL † , % in airOzone Depletion 4 16Potential (ODP)Atmospheric Lifetime, yrs 15 65The AMMTIAC Quarterly, Volume 6, Number 1 11 http://ammtiac.alionscience.com

Table 2. Historical halon applications within the military.ApplicationHalonComputer Centers 1301 & 1211Command Centers 1301Research Facilities 1301Aircraft Engine Nacelles 1301 & 1211Aircraft APU 1301 & 1211Aircraft Dry Bay 1301Aircraft Cargo Bay 1301Armored Vehicles: Engine Compartment 1301 & 1211Armored Vehicles: Crew Compartment 1301Armored Vehicles: Portable Extinguisher 1301 &1211Airfield Flightline & Crash Rescue Vehicle 1211Naval Vessels: Machinery & Engine Space 1301Naval Vessels: Electrical Compartment 1301Naval Vessels: Flammable Liquid Storeroom 1301guishment of a fire occurring anywhere within the protected enclosure.Halon 1211 became preferred for streaming applicationswhere the agent is directed as a stream towards a fire using portableextinguishers or localized fixed systems.The wide adoption of the halons was based on the fact that theyoffered a unique combination of properties that could not be foundin any other compounds. Halons are clean agents that do not leaveany residue or require extensive cleanup following their use. Theyare also highly effective fire suppressants, chemically and physicallystable, have acceptable toxicity, and were relatively low in cost. Thisunique combination of properties makes the halons ideal agents forthe protection of expensive, sensitive, and mission-critical assets.Halons found widespread use in an array of military applications,including the protection of computer and command centers,research test facilities, and an amalgam of land, sea, and air-basedmilitary equipment. Table 2 lists a selection of military applicationsthat have employed halons.A HALON ACHILLES HEEL IS DISCOVEREDIn 1974, the work of Rowland and Molina called attention to thesignificant effect that chlorine and bromine containing compoundsreleased into the atmosphere have on stratospheric ozone levels.[2]This included the halons. Production of new halon was subsequentlyeliminated in developed countries beginning in January of 1994under the Copenhagen amendments to the 1987 MontrealProtocol. In addition, the United States’ passage of the Clean AirAct of 1990 led to the development of the Significant NewAlternatives Policy (SNAP) Program, which evaluates and regulatessubstitutes for ozone-depleting chemicals (ODSs). Under thisprogram the EPA is authorized to identify and publish lists ofacceptable and unacceptable substitutes for ODSs. The SNAPprogram specifically lists fire suppression and explosion protectionas a category for review.THE HALON TRANSITION ERASignificant efforts have been made to find clean agent replacementsfor halon extinguishants. Even though numerous substitutes havebeen commercialized, halons often provide unparalleled overallperformance. For this reason, they are still specified in some criticaldefense and civilian applications. Currently, however, there are nofacilities, worldwide, that produce halons for fire extinguishingapplications. As a result, supplies are obtained from stockpiles orrecycled from decommissioned systems.The ideal halon replacement would be clean, leaving no residue,and have a high fire extinguishing efficiency for Class A, B and Cfires, low chemical reactivity, and long term storage stability. Itshould also be non-corrosive to metals, have a high material compatibility(metals, plastics, elastomers), low toxicity, and be environmentallyacceptable (no contribution to ozone depletion or climatechange). To date, no halon replacement has been developed whichsatisfies all of these requirements.Table 3 lists the commercially available clean agent options forthe halons. For purposes of discussion and comparison they arearranged into four groups: inert gases, hydrofluorocarbons (HFCs),hydrochlorofluorocarbons (HCFCs), and perfluoroketones (PFKs).INERT GASESThe inert gas agents listed in Table 3 extinguish fires by reducing theatmospheric oxygen content from 21% to between 12 and 15%. Atthese levels, most ordinary combustibles will not burn. Care mustbe taken, however, since asphyxiation signs begin below 12%, withoxygen levels below 10% being extremely dangerous. Inert gasagents are clean since no corrosive residues form following extinguishment.They are also electrically non-conductive, chemicallynon-reactive, have low toxicity, and do not contribute to ozonedepletion or climate change.The inert gas agents cannot be compressed to liquids and, as aresult, can only be stored as high pressure gases. Thus, inert gasextinguishing systems require the use of high pressure storage cylin-Table 3. Clean agent options for halon replacement.Chemical Class Designation Chemical Formula Applications Trade NameInert Gases IG-541 N 2 (52%) + Ar (40%) + CO 2 (8%) Total flooding Inergen ®‡IG-55 N 2 (50%) + Ar (50%) Total flooding Argonite §IG-01 Ar Total flooding Argotec |IG-100 N 2 Total flooding N-100 #Hydrofluorocarbons (HFCs) HFC-227ea CF 3 CHFCF 3 Total flooding, Streaming FM-200 ®**HFC-125 CF 3 CF 2 H Total flooding FE-25 ††HFC-23 CF 3 H Total flooding FE-13 ††HFC-236fa CF 3 CH 2 CF 3 Streaming FE-36 ††Hydrochlorofluorocarbons (HCFCs) HCFC Blend B CF 3 CHCl 2 + CF 4 + Ar Streaming Halotron ®‡‡ IPerfluoroketones FK-5-1-12 CF 3 CF 2 C(O)CF(CF 3 ) 2 Total flooding Novec §§ 1230The AMMTIAC Quarterly, Volume 6, Number 1 12 http://ammtiac.alionscience.com

Table 4. Clean agent comparisons to Halon 1301.Desirable Feature Halon 1301 Inert Gases HFC’s HCFCs PFKsHigh weight efficiency + + + + + + +Gas at ambient temperature + + + +Low chemical reactivity + + + + + + + + + + +Low potential metallic corrosion + + + +Electrically non-conducting + + + + +Low Toxicity + + + + + + + +Lack of metabolism + + + + + + + + + +Low agent cost + + + + + + + +Low system cost + + + + + + + +Low number of agent cylinders + + + +Low storage volume + + + +Low system footprint + + + +Low cylinder pressure rating + + + +Low manifold pressure rating + + + +Low positive/negative pressures during discharge + + +Slow stratification + + + + + + + + +Zero ozone depletion potential + + +Zero global warming potential +VOC exempt (no contribution to smog) + + + +ders and high pressure piping, which leads to increased system costs.In addition, these systems require larger numbers of cylinders andconsequently require more storage space when compared to theother clean agents, further increasing the cost of these systems.HALOGENATED CLEAN AGENTSHydrofluorocarbons (HFCs) were initially developed, nearly 20years ago, as environmentally friendly refrigerants since they do notcontain bromine or chlorine atoms in their molecular structure –the two elements that contribute to stratospheric ozone depletion.Some HFCs also proved to be clean, safe, and effective fire extinguishants.The HFC clean agents are gases at room temperature andextinguish fire predominantly via heat absorption. In other words,they remove heat from the fire until it can no longer be sustained,and is extinguished. HFC agents are clean, electrically non-conductive,and characterized by low chemical reactivity, low toxicity, andminimal environmental impact. The HFC clean agents can bestored as liquefied compressed gases, requiring fewer cylinders andstorage space than the inert gas agents. Additionally, their use doesnot require high pressure cylinders or piping.HYDROCHLOROFLUOROCARBONS & PERFLUOROKETONESHydrochlorofluorocarbons (HCFCs) are similar to the HFCs inmost properties, but are characterized by a non-zero ODP; thus,HCFCs are slated for eventual phaseout under the provisions ofthe Montreal Protocol. The perfluoroketone agent differs fromthe halons, inert gases, HFCs and HCFCs in that it is characterizedby relatively high chemical reactivity and is a liquid at roomtemperature.A summary comparing the qualitative differences between theextinguishant classes relative to Halon 1301 is found in Table 4. Themost significant feature illustrated by this table is that each class ofextinguishant has strengths and weaknesses. Selection must be basedon the criteria listed at the beginning of this discussion along withdetailed knowledge of the specific project requirements.Table 4 shows that the HFCs, followed by the inert gases, providethe best overall combination of the properties desired in aTable 5. Agent quantities required to protect a 100 m 3 enclosure.Agent Class A Hazard Class B HazardVol % Wt., Kg Vol% Wt., KgIG-541 40.0 72.4 43.9 81.9HFC-227ea 7.0 54.8 8.7 69.4Table 6. Clean agents in military applications.ApplicationAgentComputer centersHFC-227ea, IG-541Command centersHFC-227ea, IG-541Research facilitiesHFC-227ea, IG-541Aircraft engine nacellesHFC-125Aircraft APUHFC-125Aircraft dry bayInert gas generating systemsArmored vehicles: engine compartmentHFC-227eaArmored vehicles: crew compartment HFC-227ea/sodium bicarbonateAirfield flight line & crash rescue vehicle HCFC Blend BNaval vessels: machinery & engine space HFC-227eaNaval vessels: electrical compartmentHFC-227eaNaval vessels: flammable liquid storeroom HFC-227eahalon replacement. In fact, the most widely employed halonreplacements for military applications are FM-200 ® (HFC-227ea)and Inergen ® (N 2 /Ar/CO 2 ). Table 5 compares the mass and volumepercent requirements for FM-200 ® and Inergen ® . Class A Hazardsinclude ordinary combustible materials such as wood, cloth, paper,rubber, and many plastics. Class B hazards include flammable liquidsgreases, oils, solvents, and flammable gases. Military applicationscurrently employing clean agent halon replacements are listedin Table 6 and shown in Figure 1.CONCLUSIONSignificant advances have been made in identifying replacementproducts for Halons 1211 and 1301. To date, no alternative hasbeen developed that satisfies the requirements of an ideal halonThe AMMTIAC Quarterly, Volume 6, Number 1 13 http://ammtiac.alionscience.com

Stryker: Crew compartment (HFC-227ea)USS Ronald Reagan (CNV-76): Engine room (HFC-227ea)F-22 Raptor: Engine Nacelle (HFC-125)V-22 Osprey: Engine Nacelle (HFC-125) and Dry bay (InertGas)USCG Patrol Boats: Engine Room (HFC-227ea)Figure 1. DoD systems utilizing clean extinguishants.USMC AAAV: Crew Bay (HFC-227ea)Command and Communication Centers, Research Facilities:HFC-227ea, IG-541replacement. Accordingly, all of the current commercial optionscome with trade-offs; HFCs provide the best overall combination ofdesired properties, followed by the inert gas agents. This necessitatesa thorough understanding of system requirements and of the extinguishant’sperformance envelope and hardware design. Althoughresearch efforts continue in an attempt to identify viable halonreplacements, the attainment of a molecule that possesses all of thedesired properties of the ideal halon may not be achievable. Thus,agent selection will continue to be application-specific, requiringconsideration of the performance, safety, and environmental characteristicsof the different clean agents.NOTES & REFERENCES*NOAEL is the volume concentration at which there are no observedadverse effects under test conditions.†LOAEL is the lowest observable adverse level concentration.‡Inergen is a registered trademark of Ansul, which is a registered trademarkof Tyco Fire Suppression and Building Products.§Argonite is a registered trademark of Ginge-Kerr Danmark A/SCorporation.|| Argotec is a registered trademark of Minimax GmbH Corporation.#NN-100 is a trademark of Koatsu Co. Ltd.**FM-200 is a registered trademark of E. I. Du Pont De Nemours andCompany Corporation.††FE-25, FE-13, and FE-36 are trademarks of E. I. du Pont de Nemoursand Company.‡‡Halotron is a registered trademark of American Pacific Corporation.§§Novec is a registered trademark of the 3M Company Corporation.[1] “Final Report on Fire Extinguishing Agents for the Period September 1,1947 to June 30, 1950,” Purdue Research Foundation, Lafayette, IN, 1950.[2] Molina, M.J., and F.S. Rowland, “Stratospheric Sink for Chloro -fluoromethanes: Chlorine Atom Catalyzed Destruction of Ozone,” Nature,Vol. 249, 1974.[3] Robin, M.L., “The Role of HFCs in Global Fire Protection,” DuPontPublication K-22197, 2009.Edward W. Tokarsky, Ph.D., has been with DuPont for over 31 years and is currently a Senior Technical Consultant in the Chemicals andFluoroproducts business. During his career he has been involved with technical and marketing developments in Kevlar ® , Nomex ® , Teflon ® , andmost recently, specialty fluorochemicals for fire extinguishants. In his current assignment, Dr. Tokarsky is responsible for DuPont’s line of clean agentfire extinguishants.Mark L. Robin, Ph.D., is a Senior Technical Services Consultant for DuPont whom has over 20 years of experience in the fire suppression industry.He has been extensively involved in the development, testing, and approval of halon alternatives; participates on numerous fire suppressionrelated technical committees; and is the recipient of a US EPA Stratospheric Ozone Protection Individual Award, presented for his efforts in thedevelopment of halon replacements and international standards regulating their use.The AMMTIAC Quarterly, Volume 6, Number 1 14 http://ammtiac.alionscience.com

AMMTIAC DirectoryTECHNICAL MANAGER/CORDr. Khershed CooperNaval Research LaboratoryCode 63544555 Overlook Ave, SWWashington, DC 20375202.767.0181Email: cooper@anvil.nrl.navy.milDEFENSE TECHNICAL INFORMATION CENTER(DTIC) POCGlenda Smith, DTIC-I8725 John J. Kingman Road, Ste 0944Ft. Belvoir, VA 22060-6218703.767.9127, Fax: 703.767.9174Email: gsmith@dtic.milAMMTIAC DIRECTORMicheal J. Morgan201 Mill StreetRome, NY 13440-6916937.431.9322 x103, Fax: 315.339.7107Email: mmorgan@alionscience.comAMMTIAC DEPUTY DIRECTORChristian E. Grethlein, P.E.201 Mill StreetRome, NY 13440-6916315.339.7009, Fax: 315.339.7107Email: cgrethlein@alionscience.comMATERIALS TECHNICAL DIRECTORJeffrey D. Guthrie201 Mill StreetRome, NY 13440-6916315.339.7058, Fax: 315.339.7107Email: jguthrie@alionscience.comCONTRACTS FACILITATORJudy E. Tallarino201 Mill StreetRome, NY 13440-6916315.339.7092, Fax: 315.339.7107Email: jtallarino@alionscience.comMANUFACTURING TECHNICAL DIRECTORChristian E. Grethlein, P.E.201 Mill StreetRome, NY 13440-6916315.339.7009, Fax: 315.339.7107Email: cgrethlein@alionscience.comTECHNICAL INQUIRY SERVICES MANAGEROwen R. Conniff201 Mill StreetRome, NY 13440-6916315.339.7026, Fax: 315.339.7107Email: oconniff@alionscience.comNON-DESTRUCTIVE EVALUATIONAND TESTING TECHNICAL DIRECTORDavid S. Forsyth9063 Bee Caves RoadAustin, TX 78733-6201512.263.2101 x223, Fax: 512.263.3530Email: dforsyth@tri-austin.comFor a listing of upcoming materials, manufacturing & testing related events, please visit our website:http://ammtiac.alionscience.com/calendar