Energy Absorption Mechanisms in Unidirectional Composites Subjected to Dynamic Loading Events
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This report documents the numerical modeling that was conducted to study the failure modes in dynamically loaded, unidirectional UD fibrous composites. The purpose of this research was to determine how to increase energy absorption capacities during severe dynamic loading events. Energy absorption mechanisms are generally composed of elastic, inelastic, kinetic, frictional, acoustic, thermal, and dissipative sources. In this study, the inelastic energy absorption mechanisms associated with damage at the interfacial and constituent levels were numerically characterized through four admissible failure modes fiber breakage, matrix shearing, fibermatrix debonding, and fibermatrix delamination. Finite element models were developed for cross-ply UD composites constructed of ultrahigh molecular weight polyethylene UHMWPE fibers separately reinforced with compliant Kraton-D polymer and rigid epoxy matrix materials. The energy absorption capacities of these damage mechanisms were contrasted for three different dynamic loading cases including blast, shock, and ballistic impact. The results suggest that the energy loss due to cohesive failure modes is significant for each loading case and, therefore, must be included to ensure model robustness. Fiber breakage and matrix shearing, however although not significant in blast and shock events must also be included in ballistic impact cases. Fiber breakage during ballistic impact was the dominant energy absorption mechanism followed by matrix shearing. As is shown for a given perforating ballistic impact case, this study revealed that the epoxy-reinforced laminate captured 4.22 more kinetic energy of the projectile than did the Kraton-reinforced laminate.
- Laminates and Composite Materials