OS-C501

Recommendations

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Offshore Standard DNV-OS-C501, November 2013 Sec.5 Materials – sandwich structures – Page 92 7.2.3 The influence of such additives or fillers on the basic mechanical properties shall be evaluated. 7.3 Fire resistance 7.3.1 Fire resistance describes the remaining strength of a composite structure under a fire. 7.3.2 As a first estimate of fire resistance, the temperature-dependent properties as described in [5.2] can be used. 7.3.3 The temperature within a sandwich component can be calculated by means of appropriate models. 7.3.4 If chemical reactions can occur within the sandwich component, their influence on the temperature distribution shall be considered. 7.3.5 Through thickness properties and core properties shall be carefully evaluated, especially in the region of joints. Guidance note: A panel with stiffeners may loose most of its stiffness if the stiffeners delaminate from the panel due to the fire. 7.4 Insulation ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 7.4.1 The properties of the insulation with respect to fire reaction and fire resistance shall be evaluated. 7.4.2 Special consideration shall be given to the joints of the insulation and the method the insulation is attached to the component. Attachment points and joints may create hot spots in the component. 7.4.3 All large scale testing shall be done with jointed insulation and the same attachments as used in the real application. 7.5 Properties after the fire 7.5.1 A fire is usually seen as an accidental load case and properties after the fire shall be evaluated for each individual case. 7.5.2 If the temperature has locally exceeded the Tg of the component it is very likely that permanent damage has been made to the component in that area. 7.5.3 If the temperature remained locally under Tg damage may be introduced due to overloads from other parts of the structure. 8 Qualification of material properties 8.1 Introduction 8.1.1 All material properties needed to describe the performance of a component shall be documented. 8.1.2 As a general principal, material properties should be obtained form test results of laminates that represent the laminates of the component as closely as possible. 8.1.3 Material properties may be documented by the following methods: — direct measurements — qualification against representative data — qualification against manufacturers data — qualification against data from the open literature — qualification by component testing. 8.1.4 Each individual material property may be qualified by any of the different methods. 8.1.5 Which data can be used for qualification depends mainly on two aspects: — were the data obtained form laminates that are similar to the laminates used in the component — were the data obtained from reputable sources. 8.2 General test requirements 8.2.1 All relevant information about the material tested, the test method, and the test conditions shall accompany test results. The information requested in [1.2] shall be provided. 8.2.2 Static test results shall be reported as mean, standard deviation, coefficient of variation, and number of test specimens. The characteristic values of static tests shall be calculated as described in Sec.4 [2.4]. DET NORSKE VERITAS AS
Offshore Standard DNV-OS-C501, November 2013 Sec.5 Materials – sandwich structures – Page 93 8.2.3 Long-term test results shall be reported as mean regression curve, standard deviation with respect to time or cycles, number of test specimen, range of test time or number of cycles. Test points shall be spread out relatively evenly over the logarithmic test period. The characteristic values of long-term tests shall be calculated as described in Sec.4 [3.11]. 8.3 Selection of material qualification method 8.3.1 The test results shall apply to the core and adhesive used in the component to be designed and built. Test results are only applicable if the test core and adhesive and the sandwich structures are similar enough that the test results are valid or conservative for the actual component. 8.3.2 If a core material is the same as an already tested material no further testing is required. The same core material means: — same basic material type, e.g. balsa, honeycomb, PVC foam core — same core manufacturer, same trade name — no change with respect to cell structure, processing method, raw materials used. 8.3.3 If a core material is similar to an already tested material qualification against a representative material may be carried out. Requirements for similarity are given in [8.6], requirements for representative data are given in [8.5]. 8.3.4 Direct measurements as described in [8.4] shall be carried out if [8.3.2] or [8.3.3] cannot be applied. 8.3.5 Any change of adhesive requires re-qualification of the properties related to the adhesive performance as described in [8.6]. 8.4 Direct measurement 8.4.1 The various properties of a composite may be measured directly for a particular material. Data will be valid for that particular material that was tested. The material shall be characterised as required in section [1.2]. 8.4.2 The test methods described in App.D should be preferred. 8.5 Representative data 8.5.1 If a sufficient number of direct measurements is available, data may be used to establish a set of representative data for a material property. To be considered representative, data should be based on at least 15 measurements per property. Other materials can be compared against the representative data as described in [8.6]. 8.5.2 Representative data are most useful if they can be used for a fairly wide range of materials. This will also allow to pool data of different properties that were obtained from slightly different materials. Requirements for to the individual materials that can be put into one group of representative data are given in Table 5-10. Table 5-10 Requirements for individual material to be part of representative data Constituent core material(s): Generic core type (e.g. foam, honeycomb, balsa etc.) Core trade name Type of core (e.g. linear foam) Type/ characteristics of microstructure Core manufacturer Batch number Glass transition temperature Constituent adhesive material(s): Generic adhesive type (e.g. epoxy, polyester) Specific adhesive type trade name Specific adhesive type batch number Catalyst Accelerator Fillers (trade name and batch number) Additives (trade name and batch number) Requirements to group measurements from different sandwich cores Same for all tests Same for all tests Same for all tests Same for all tests Same for all tests Not relevant Lowest from all tests Same for all tests Same trade name* Not relevant Same trade name* Same trade name* Same trade name* Same trade name* DET NORSKE VERITAS AS
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OS-C501

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