Residual Strength prediction of the Carbon/Epoxy plates under Low-Velocity Impact

In this study, the residual strength of the carbon/epoxy composite plates exposed to the thermal cycles and subjected to low-velocity impact was evaluated using an experimental procedure. Composite plates with a layup of [45/02/-45/902]s and thickness of 2.9 mm under three impact energy levels of 10J, 15J, and 20J and exposed to 200 thermal cycles in the range of -30 to 65° C went under low-velocity impact and compression after impact tests. In performing impact tests, a drop weight test device was used to investigate the behavior of damaged composites, force-time, force-displacement, and energy-time curves at all test temperatures were analyzed. Finally, the effect of temperature and associated damages at different levels of impact was evaluated using radiographic analysis and optical microscopy. Applying 200 thermal cycles in the temperature range of -30 to 65 ° C caused small cracks in the matrix and reduced the energy absorption of the samples. The highest drop in compressive strength is related to the highest impact energy, 20 J, which has a 31.12% decrease in strength. The thermal cycle at different impact energy levels of 10J, 15J, and 20J has led to an increase in the stiffness and compressive strength of the composite specimens. Finally, material parameters of the semi-empirical Caprino model to estimate the residual compressive strength of the carbon/epoxy plates under low-velocity impact and thermal cycles are obtained.