Transient-dynamic crush testing of carbon composite material at close-to-cryogenic temperatures

This paper deals with quasi-static and transient-dynamic crush testing of carbon composite material at close-to-cryogenic temperatures. Self-supported crush specimens of trapezoidal shape were fabricated from Cycom 6k HTA 5 HS carbon fabric material infiltrated with HexFlow RTM6 resin. Crush tests were performed at the temperatures T 1 ≈ 20°C, T 2 = −55°C, and T 3 = −170°C, as well as at loading rates of 20 mm/min and 2 m/s. A new test setup was used that enabled precise temperature control at close-to-cryogenic conditions in particular for high strain-rate testing. The steady-state crush stress (SSCS) and mass-specific energy absorption (SEA) are determined and compared for varying loading rates and temperatures. Main objective of this study is to obtain a first insight in trends for transient-dynamic crush performance at low temperatures which is why only two tests per configuration were performed. The test results indicate SSCS and SEA reduction for increasing loading rate and decreasing temperature. Strain-rate dependency showed twice the SSCS and SEA reduction at low temperatures compared to room temperature. Concerning the crash-relevant dynamic loading, the SSCS and SEA values are reduced by −15% from T1 ≈ 20°C to T2 = −55°C while the reduction is −19% from T1 ≈ 20°C to T3 = −170°C. Summarized, compared to quasi-static test data at room temperature, the total reduction for crush loading at −170°C and 2 m/s is −28% for SSCS and SEA. As a novel aspect, this result was experimentally determined under precisely controlled close-to-cryogenic temperatures during high-speed testing.