Influence of temperature and impact energy on low velocity impact damage severity in CFRP

This study focuses on the effect of temperature and impact energy on the damage in CFRP under low velocity impact. Quasi-isotropic laminates with a thickness of 4.1 mm were impacted with energies between 8 and 21J at temperatures ranging between 20 and 80°C. The resulting damage was assessed using ultrasonic C-scans, radiography and confocal microscopy. The residual strength was evaluated utilizing compressive tests at 20°C. It was found that delamination size is decreasing with increasing temperature. However, severe fibre failure on the impacted side occurs at elevated temperatures. This increases the visual damage detectability on the impacted side heavily while decreasing it on the opposite side. Nevertheless, the residual compressive strength is mainly dependent on the delamination area. Different impact energies can have the same effect on the residual strength, when impacted at different temperatures. As a result, visual damage severity does not correlate with the residual compressive strength.