Strain Rate Effect On The Compressive Behavior Of 3-D Braided Composites

The mechanical properties of 4-step 3-D braided composites at high strain rates are important in evaluating the responses of this kind of composites at dynamic and impulsive loading. However, there are no references concerned with this topic so far.The E-glass filament tows were used in manufacturing of 3-D braided preform with 4-step lxl technique. Two kinds of braided preforms, namely 8x4 array and 8x6 array of rectangular cross-section, were braided. And the resin transfer molding technique (RTM) was used to fabricate 4-step 3-D braided E-glass/epoxy composites.The in-plane and out-of-plane compressive properties of E-glass/epoxy 4-step 3-D braided composites at strain rates from 300/s to 3500/s were tested with split Hopkinson pressure bar (SHPB). The compressive properties at quasi-static strain rate (0.001/s) were also tested on New MTS 810 and compared with those in high strain rates. The stress strain curves are rate sensitive in both directions, and compressive stiffness and compressive deformation are also sensitive to the strain rate. A higher strain rate sensitivity of compressive stiffness was found between quasi-static and high strain. The compressive stiffness is linearly increased with the strain rate. At in-plane direction, the compressive deformation mode was observed to have transitions from axial-compression deformation to shear deformation at increasing strain rates, while only the compressive deformation was found at out-of-plane direction. The maximum compression stress andcorresponding strain have not regular tendency as the increasing of strain rate.