The Best of Both Worlds: Hybrid Ship Hulls Use Composites & Steel

To InstronUniversity of MaineE-glassbeamSteelbeamUniversity of California–Los AngelesFigure 6. Development of Joint Concepts, and Understanding Failure Mechanisms.SteelLarge Scale TestingFigure 5 shows the large, built-up composite-to-steel joints,which will be tested soon. In addition, a proposed half-scale hullmay be tested in the future to gain more confidence in the analysisof large scale composite/steel joints under complex sea loadand UNDEX conditions.FRP AdherentBasic Research on Compositeto Steel JointsThe wide application of compositesin future ships and submarines (e.g.composite topside, composite mast,composite sail, hybrid hulls etc.), hasopened a new field of research injoints. Several studies are underway tounderstand the behavior of compositeto steel joints. These investigationscover three areas: development of joiningmechanisms, understanding failurebehavior under cyclic and dynamicloads, and development of computationaltools for joint analysis. Figure 6hightlights several studies for developmentand analysis of various joiningmechanisms: bolting, adhesive joining,composite fasteners, and compliancematching methods.Figure 7 shows some of the theoriesand experiments related to dynamicfailure and friction laws that should beconsidered in the failure analysis ofthese large joints. It is imperative thatfriction not be ignored along the entire circumference of a hull(or length of ship topside) after failure of the fasteners and theinitiation of interfacial cracks.Figure 8, shows some of the analysis and computational techniquesunder development to allow the designer to predict failureof interfaces under cyclic fatigue and dynamic loading. TheyinsertUniversity of California–San DiegoLehigh UniversityCalifornia Institute of TechnologySteelHarvard UniversityBrown UniversityBrown UniversityFigure 7. Theoretical and Experimental Methods for Understanding and Measuring Friction at Interfaces of Composite/Steel Joints.The AMPTIAC Quarterly, Volume 7, Number 3 59

Mathematical formulas,rules, weight ...IMPACT LOADINGAutomatic learning toolsGlobal ScaleComponent ScaleMaterial ScaleRensselaer Polytechnic InstituteUniversity of California–San DiegoFigure 8. Development of Analytical Methods for Analysis of Hybrid Ships.cover the use of neural networks and expert systems, as well as thedevelopment of multi-scale computational methods (covering thescale from interface details to the full scale structure.)APPLICATION OF HYBRID HULLThe hybrid hull concept was conceived to enable the use of compositesin the structure of large combatants. The emerging needfor fast craft in the Navy however, brought about a new possibilityfor hybrid construction. Fast craft require high fatigueresistance and the use of low density materials like aluminum orcomposites. Where many aluminum alloys suffer from poorfatigue performance, composites can be made to possess excellentfatigue resistance, but may lack the stiffness for some of the hullforms of the proposed fast ships. Figure 9 shows some conceptsof hybrid construction envisioned for fast ships.Application of Hybrid HullPentamaranTheater Support VesselTrimaranCatamaranTheater Logistics VesselSurface Effect ShipFast Patrol BoatFigure 9. Concepts of Hybrid Construction in Fast Craft.60The AMPTIAC Quarterly, Volume 7, Number 3