基于红外热成像的编织复合材料低速冲击和冲击后压缩试验研究

The damage and failure mechanism of two-dimensional triaxially braided composite (2DTBC) under low-velocity impact and compression after impact (CAI) was experimentally investigated through tests with various impact energies (5, 10, 20 and 30 J). The low-velocity impact specimens were prepared according to the ASTM D7136 standard and tested using the Instron drop tower 9250HV with a hemispherical punch, and CAI tests were carried out on an Aowei PLD-250 fatigue machine following the ASTM D7137 standard. An infrared thermal imaging camera was employed to monitor the temperature distribution of the specimens during the low-velocity impact and CAI tests. Delamination damage of impacted specimens was characterized by an ICS-Ⅱ ultrasonic C-scanner. The relationship between impact energy and residual compression strength of 2DTBC after impact load was compared and analyzed. The evolution of the temperature field and its sensitivity against impact energy were discussed based on the infrared image data. Regarding the CAI tests, the global strain field was measured using the digital image correlation (DIC). Combining the thermal and deformation fields, and the optical failure images, the compression failure behavior of 2DTBC after impact of different energies were systematically investigated, validating the feasibility of infrared thermal imaging technology on characterizing the damage and failure behavior of braided composites. The experimental results show that the temperature field contours in low-velocity impact and CAI tests of braided composites are significantly correlated with braided architecture. The magnitude of temperature rise during the low-velocity impact test increases rapidly with the increase of impact energy, while the magnitude of temperature rise during the CAI test decreases with the increase of impact energy. Moreover, the maximum temperature rise is about 56.2 ºC in the 30 J low-velocity impact test. The delamination area is found to increase with the increase of impact energy, and the residual compression strength after impact decreases with the increase of impact energy. The residual compression strengths ratios are 90.9%, 82.2%, 73.8% and 65.8% for specimens after 5, 10, 20 and 30 J impacts, respectively. Through this study, we demonstrate that infrared thermal imaging camera can clearly capture the temperature rise phenomenon of composite specimens, which is caused by the releasing of fracture energy at the failure instant. More notably, the temperature contour can better reflect the damage location and failure characteristics than the global strain field.