Damage development in stitch bonded GFRP composite plates under low velocity impact: Experimental and numerical results

Damage development due to impact needs to be understood to evaluate the consequences of impact on composite structures. This study concentrates on modelling and measuring damage development due to low velocity impact on thick industrial composites made from glass fibre epoxy by vacuum-assisted resin infusion. Cross-plied laminates were tested with different impact energy and different number of interfaces (clustering). Results were compared to a 3D finite element analysis. Interfaces and their damage development were modelled with cohesive elements. Intra ply properties were modelled by progressive failure analysis. Many elements and large memory use were needed to obtain sufficient modelling accuracy. However, all input parameters of the model were based on widely available and independently obtained material properties. Impact force and time to initiate damage and maximum force were measured and related to impact energy and clustering. Damage development was monitored optically in the translucent material for all test cases. The results show that the numerical model using only simple and independently measured material data was able to predict the impact behaviour for the different energies and different stacking sequences. </jats:p

Numerical and experimental investigation of impact on filament wound glass reinforced epoxy pipe

Impact on glass fibre reinforced (GFRE) pipes, produced by filament winding, was experimentally and numerically tested. The influence of ring stiffness and impact energy on the residual structural strength was evaluated by testing resistance against implosion due to external hydrostatic pressure. An advanced 3-D finite element (FE) model, based on the combined use of interlaminar and intralaminar damage models, was used for simulating impact events. Puck and Hashin failure theories were used to evaluate the intralaminar damages (fibre failure and matrix cracks). Cohesive theory, by mean of cohesive elements, was used for modelling delamination onset and propagation. Material data for the models were based on commonly measured ply properties. The numerical simulations were able to accurately predict the impact forces and damage development of the experimental impact events. Pipes with high ring stiffness have high resistance to external pressure, but they were found to develop more impact damage and have subsequently less resistance to external pressure when damaged.</jats:p