High strain rate behavior of 4-step 3D braided composites under compressive failure
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The out-of-plane and in-plane compressive failure behavior of 4-step 3D braided composite materials was investigated at quasi-static and high strain rates. The out-of-plane and in-plane direction compressive tests at high strain rates from 800/s to 3,500/s were tested with the split Hopkinson pressure bar (SHPB) technique. The quasi-static compressive tests were conducted on a MTS 810.23 tester and compared with those at high strain rates. The comparisons indicate that the failure stress, failure strain and compressive stiffness both for out-of-plane and in-plane loading directions are rate sensitive. For example, the failure stress, failure strain and stiffness are 55.19 MPa, 6.70% and 1.35 GPa respectively as opposed to 145.00 MPa, 1.21% and 13.50 GPa respectively for strain rate of 2,500 s−1 under in-plane compression. The 3D braided composites have higher values of failure stress and strain for out-of-plane than for in-plane compression at the same strain rate; however, the in-plane compression stiffness is higher than that of out-of-plane compression at high strain rates. The compressive failure mode of 3D braided composites in the out-of-plane direction is mainly shear failure at various strain rates, while for the in-plane direction it is mainly cracking of matrix.
KeywordsHigh Strain Rate Failure Strain Compressive Failure Braided Composite Compressive Stiffness
The authors of this paper gratefully acknowledge the supports of the Chinese National Science Foundation (NSFC 19902016) and the Natural Science Foundation of Shanghai Municipality (04ZR14009). The author of Bohong Gu, also acknowledges the helps from Mr. Alexi Rakow, Ph.D. Candidate of Structures and Composites Laboratory, Stanford University for revising English of the paper when the author is a visiting scholar at this laboratory. Furthermore, authors gratefully appreciate the constructive opinions of anonymous reviewers which lead to the further analysis of compression damage mechanism under different strain rates.