Estimation of residual flexural strength of unidirectional GFRP composite laminates under repeated impact load

The aim of this study is to investigate the effect of low-velocity multiple impacts at ambient (35C) and elevated temperature (65C and 85C) on unidirectional glass fiber reinforced plastic (GFRP) composites. Low-velocity repeated impact tests were conducted using a falling weight tower at a constant velocity of 1.5 m/s. The dominant parameters such as energy, contact force, and deflection were recorded during multiple impacts. The residual strength of laminates following repeated impact was evaluated by conducting three-point bending tests with acoustic emission (AE) real time monitoring. The temperature was revealed to play a key role in the impact response of composite materials, especially due to the progressive softening of the epoxy matrix. The nature and extent of damage during multiple impacts at ambient and elevated temperatures was investigated using real time AE monitoring: this analysis indicated delamination as a predominant failure mode, whose extent and criticality depended on temperature and number of impact events.