A three-dimensional progressive damage FE model for GFRP composites under monotonic loading

An anisotropic non-linear 3-D progressive damage constitutive model for composite materials under monotonic loading (both tension and compression) was presented. It was implemented in a 3-D solid finite element of a commercial FEA code. Material non-linearity was taken into account, based on experimental data at the ply level. Puck's failure theory for general 3-D stress state was also implemented for the determination of the failure onset of each ply along with new, simple stiffness degradation rules for the simulation of the mechanical behaviour of the damaged ply, including a very limited number of fitting parameters. The parameters were derived by comparing the simulation results against experimental data of [±45]S and 60° off-axis uni-directional coupons in tension. The model was validated by comparing its results to experimental data of glass/epoxy continuous fibre reinforced composite laminates of various lay-ups under axial, static, tensile and compressive loading. The effect of the FE mesh and the load increment was investigated. It was proven that 6 layers of FE per UD ply across the thickness direction were enough to capture the 3-D stress state effects in all cases. The FE model width was proven to have an important influence on the predictions. The failure modes predicted by the FE analysis were also compared against photos of failed specimens. The results of the MD laminates simulated were very good and the failure modes predicted were in good agreement with the damage observed on the failed coupons.