High temperature shear strength of T650-35 / HFPE-II-52 polyimide matrix unidirectional composite

The shear strength of a 4-ply unidirectional composite laminate consisting of carbon fibers (T650-35) and a polyimide matrix (HFPE-II-52) was measured over a temperature range of 25 to 315C. The tests were performed using a Iosipescu test sample, modified to provide a more uniform shear stress distribution across the gauge section and loaded with an Arcan type test fixture. The test specimen design is based on the results of an extensive finite element study. Shear strength tests were performed on dry, 50% RH and 100% RH moisture saturated samples. Results of the experiment show that shear strength decreases from approximately 120 MPa at 25C to 60 MPa at 315C and that moisture saturated samples have a 5-10 MPa lower shear strength than dry samples.