Effects of high strain rate compression on the mechanical properties of a uniweave AS4/3501-6 composite laminate with through-thickness stitching

Abstract

Polymer matrix composites offer excellent mechanical properties such as high specific strength and stiffness, making them attractive for applications in several naval, aerospace, automotive, and recreational-sports structural components. Although many composite materials are selected for applications where high strain rate loading is probable, little is known of their response to shock loading. Material properties can vary significantly with strain rate. Therefore, the use of static properties in the analysis and design of structures which undergo dynamic loading may unfortunately lead to very conservative, overweight designs or lead to designs which fail prematurely and unexpectedly. The use of dynamic material properties ensures that designs are optimized for structural integrity and weight efficiency when subjected to dynamic loading. In this study, a Split Hopkinson Pressure Bar is used to obtain high-strain-rate, compressive mechanical properties of a uniweave AS4/3501-6 composite laminate with and without reinforcement stitching in the through-thickness. Due to geometry restrictions on the test specimens, stitched specimens contain only a single, through-thickness stitch. Therefore, while this study may not give insight to the macroscopic benefits of reinforcement stitching, it does give insight to stitching effects local to the stitched area. For both in-plane and out-of-plane directions, the compressive mechanical properties of yield stress, yield strain, ultimate strength, ultimate strain, and modulus of elasticity are determined for strain rates varying from 234 sec1 to 1216 sec1.