Comparative Assessment of Finite Element Modelling Strategies for Low-Velocity Impact of Thin GFRP Laminates

The primary objective of this study is to assess how different finite element modelling strategies influence the prediction of global impact response, internal damage evolution, and computational efficiency in thin glass fibre-reinforced polymer (GFRP) laminates subjected to low-velocity impact (LVI). A detailed reference model incorporating progressive intralaminar damage, cohesive-zone-based interlaminar delamination, and explicit representation of the experimental boundary condition was first established. Alternative boundary conditions, interface, and laminate representations were subsequently evaluated using nodal constraints, tiebreak contact formulations, thick-shell elements, and an equivalent single-layer formulation. Boundary idealisation was found to introduce localised peripheral delamination under low-energy impacts, while its influence on absorbed energy decreased with increasing impact energy, falling below 1.2% at 30 J. Replacing cohesive interfaces with tiebreak contact reduced computational cost by approximately 70% while preserving the overall impact response at lower impact energies, although the predicted damage morphology diverged when extensive delamination and perforation developed. Thick-shell and equivalent single-layer formulations further reduced model complexity but showed increasing limitations once progressive damage governed the response. The results demonstrate that similar global impact responses may be obtained from models with substantially different internal damage predictions, highlighting the need to select modelling strategies according to the response quantity of interest.