Compressive failure mechanisms of fibre metal laminates with 2/1 and 3/2 configurations after low-velocity impact

The residual compressive strength after low-velocity impact (LVI) serves as a pivotal metric for assessing the damage tolerance of composite structures. This paper aims to elucidate the compressive failure mechanisms of glass fibre/aluminium fibre metal laminates (FMLs) that have incurred initial LVI damage, meanwhile illustrating the effects of fibre orientation, impact energy and laminate configuration on the compressive failure behaviours of FMLs. Initially, specific impact damage was prefabricated and examined in FMLs with 2/1 and 3/2 configurations. Quasi-static compression tests were then conducted to analyse the global force versus displacement responses and local strain evolution of FMLs during compressive loading. Furthermore, visual inspection, ultrasonic C-scan, and CT-scan were employed to explain the damage morphologies and failure mechanisms of FMLs. Finally, the comparative analysis of the compression after impact (CAI) strengths was conducted for different FMLs. The results demonstrate that fibre orientation, impact energy and laminate configuration significantly affect the compressive mechanical responses and damage morphologies of FMLs. Moreover, FMLs experience a 40-61 % decrease in compressive strength after LVI within the energy range from 35 J to 65 J. Additionally, the 3/2 configuration is a more advantageous laminate design than the 2/1 configuration in terms of specific CAI strength and residual strength ratio. This research contributes novel insights into the impact damage tolerance of FMLs, which hold promise as load-bearing structural materials in aeronautic applications.