Numerical and Experimental Investigation of Impact Behaviour of GFRP Composites
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Composites are more susceptible to impact damage than metals. While a metal structure can dissipate impact energy by yielding (plasticity), composites dissipate energy by developing damage, mainly matrix cracking, delamination and some fibre failure. Initially, the damage is often small and difficult to detect, but it can grow during service leading to severe reduction of the structural stiffness and strength. Flat panels made by vacuum assisted resin infusion and filament wound pipes were tested and modelled. These are typical commercial glass fibre composites as used in the marine and offshore industry. The influence of the clustering effect and bending stiffness on the impact behaviour was investigated. The main emphasis was put on modelling impact with a full three-dimensional Abaqus finite element model, allowing simulation of a failure mechanisms while using relatively easily available material data. An innovative test method to obtain energy release rate data for filament wound tubes was developed. Modelling intralaminar damage was done by a userdefined VUMAT subroutine based on the combined use of the Hashin failure criterion for fibre failure and the Puck criterion for matrix cracks. Interlaminar damage was modelled by cohesive elements based on the bi-linear traction separation law. The residual strength after impact was experimentally evaluated. Compression after impact tests (CAI) were used for flat panels and implosion tests for cylindrical structures. Impact forces could be predicted with 5% accuracy. The shape of damage was well described by the model while the size was typically slightly over-predicted by 10% -15%.