Overstress accommodation in notched woven-ply thermoplastic laminates at high-temperature: Numerical modeling and validation by Digital Image Correlation
Abstract
An experimental and numerical study has been conducted on woven-ply PPS-based laminates subjected to static loadings at temperatures higher than the material’s Tg. The fiber – or matrix-dominated mechanical responses of laminates with respectively quasi-isotropic or angle-ply stacking sequences have been investigated in order to emphasize the significant contribution of TP-matrix to the accommodation of overstresses near the hole as temperature increases. Even though the matrix behavior becomes highly ductile, the degree of retention of mechanical properties is quite high, and the hole factor is virtually unchanged as temperature increases in Q-I laminates. In order to understand how matrix ductility is instrumental in reducing the notch-sensitivity (−34%) of A-P laminates, a temperature-dependent and rate-independent plasticity model has been implemented into a finite element code, and validated by a Digital Image Correlation technique. The proposed model shows that the enhanced ductility of C/PPS at T > Tg significantly contributes to the accommodation of overstresses in notched laminates through an extensive plastic deformation along the ±45° fibers, resulting in a clipping of the overstrain peak. When it comes to design TP-based laminates at temperatures around or higher than Tg, the elastic–plastic numerical tool presented in this work can be useful for stress engineers willing to predict the effect of ductility on overstresses accommodation, and to calculate the decrease in notched laminates strength.