Study of the fracture behaviour in hybrid fibers reinforced thermoplastic laminates: Influence of temperature and initial notch orientation

The present work was aimed at investigating the failure of quasi-isotropic fibers reinforced thermoplastic laminates solicited at different testing temperatures. Single-edge-notch bending (SENB) tests were conducted at room temperature (RT) and at a temperature higher than the glass transition temperature (Tg) to investigate the influence of failure mode (depending on initial notch orientation) as well as matrix ductility and toughness (depending on testing temperature) on: (1) damage mechanisms - (2) critical translaminar fracture toughness Gc and (3) G-R curves evolution. The mixed mode fracture toughness GI+II,c is dramatically lower than the mode I fracture toughness GIc, with -52% and -67% decreases, at RT and 150 degrees C respectively. In 45 degrees notched specimens, most of the fracture energy (about 80%) stems from the mode I failure. Though they are not prominent on fracture, the failure mechanisms associated with mode II are instrumental in limiting the contribution of mode I on fracture behavior. Finally, though a temperature increase has very little influence on GIc, it significantly reduces the value of GI+II,c (-32%). This change primarily results from the formation of plastic-kink bands in compression that are promoted by both the ductility of the polyether ether ketone (PEEK) matrix at T > Tg and the mixed-mode failure.