Temperature effect on the low-velocity impact characteristics of glass laminated aluminium reinforced epoxy panels

Abstract

Applications of fibre metal laminates (FML) in aircraft structures involve in-service temperatures higher than 30°C up to well above 100°C. Such high temperatures could affect the FML performance. Hence, there is a need to investigate temperature effect towards the low-velocity impact response of FMLs. The purpose of this study was to evaluate the influence of increased temperature from 30 to 110°C towards the impact response of FMLs. Experimental trials were conducted at 30, 70 and 110°C to extract temperature-dependent properties of glass fibre reinforced polymer (GFRP) composite and interlaminar delamination of GFRP laminated aluminium. The experimental results obtained from the quasi-static tests at 30, 70 and 110°C and low-velocity impact tests at various impact energies were used to validate the numerical models. Explicit nonlinear code LS-DYNA was subsequently employed to develop the finite element (FE) model of the FMLs. Johnson-Cook model, Chang-Chang failure criteria and cohesive zone models were applied to simulate aluminium, GFRP and delamination, respectively. The Mode-I and Mode-II delamination and quasi-static perforation of FMLs at elevated temperatures were modelled and validated. After which, combined analysis of impact energy levels and temperatures were carried out by employing the FE quarter model. A modified property degradation model was also utilised to obtain properties at 50 and 70°C effectively with a single fitting parameter. Using the validated FE model, parametric studies were carried out to investigate the effects of varying geometrical parameters at elevated temperature. The results indicated that an increase in temperature significantly affects the low-velocity impact response and impact resistance of FMLs. Increase in temperature degrades the GFRP and GFRP/aluminium interface by a larger degree as compared to aluminium. The degradation of FMLs is progressive such that it is less significant from 30 to 70°C and more severe from 70 to 110°C. Hence, the FE modelling methodology proposed herein provides the means to simulate, predict and analyse the impact of FMLs with consideration of temperature effects. This research contributes towards the advancement of FMLs and composites for applications under high temperatures. The FE method provides a coherent and reliable way to simulate and analyse FML impact performance under different temperature conditions.