Effect of hygrothermal condition on compression after impact strength of CFRP laminates

This study investigated the combined effects of water absorption and thermal environment on compression after impact (CAI) characteristics of CFRP laminates. Specimens were immersed in 71 °C water for over 10,000 h to quantify the ratio of water absorption in the CFRP laminates. Numerical simulation based on Fick’s law was conducted to predict moisture diffusion using the measured orthotropic diffusivities. Compression tests after drop-weight impact tests were carried out at various temperatures, i.e. −54 °C, 22 °C, 82 °C, 121 °C, 149 °C, 177 °C. Delamination area and the number of transverse cracks of the wet specimen were smaller than those of dry specimens. Smaller delamination area of the wet specimens provides higher CAI strength than the dry specimens at mid-high temperatures of 22 °C, 82 °C and 121 °C. The CAI strength of the wet CFRP decreased slightly at 149 °C and significantly at 177 °C because the glass transition temperature deteriorates seriously due to the water absorption. The failure mode changes at high temperature, i.e. impact induced delamination is not the trigger of the failure but buckling induced crippling causes final failure at 177 °C.