High temperature translaminar fracture of woven-ply thermoplastic laminates in tension and in compression

The translaminar fracture behavior of three composite laminates, based on thermoplastic matrix PEEK reinforced by a woven carbon fibers obtained by consolidation process, has been studied by means of Compact Tension (CT) and Compact Compression (CC) tests. An orthotropic laminate and two quasi-isotropic laminates, have been tested at room temperature (RT) and at 150 °C (i.e. for a temperature slightly higher than the glass transition temperature Tg), with the purpose of evaluation the influence of the stacking sequence and the temperature on the damage mechanisms. The CT type tests show that the temperature influence on the overall mechanical response remains low. In contrast, the CC type tests show a decrease in the mechanical resistance and an augmentation in the global ductile behavior. By means of the 2D Digital Image Correlation and the implementation of a algorithm based on the sigma indicator (confidence interval in the area of interest), the crack propagation was measured during loading, then the G-R curves have been obtained from the compliance method. In tension, there is an increase in the translaminar fracture toughness with the laminate thickness and a slight improvement in this one due to the influence of temperature. In compression, the temperature strongly decreases the translaminar fracture toughness.