Fracture mechanics of hybrid composites with ductile matrix and brittle fibers: Influence of temperature and constraint effect

The fracture behavior of hybrid carbon and glass fiber woven-ply reinforced polyether ether ketone thermoplastic quasi-isotropic laminates is investigated. Single-edge-notch bending and single-edge-notch tensile tests were conducted at room temperature and at a temperature higher than the glass transition temperature ( T _g ) to study the influence of both the constraint effect and the temperature on the strain energy release rate in laminates with ductile polyether ether ketone matrix and brittle fibers. As failure is primarily driven by fibers breakage in tension (single-edge-notch tensile test) and in tension/compression (single-edge-notch bending), it turns out that a temperature increase has very little influence on the mode I critical translaminar fracture toughness K _Ic though the ductility of polyether ether ketone matrix is exacerbated at T > T _g . It also appears that the constraint effect has very little influence on K _Ic as single-edge-notch tensile test and single-edge-notch bending specimens have virtually the same mean value (about 45MPa. [Formula: see text]). Single-edge-notch bending specimens being characterized by a gradual failure, the G-R curves were derived from the computation of the compliance loss and the corresponding gradual crack growth in agreement with the ASTM standard E1820. From the evolution of the G-R curves at high temperature, the highly ductile behavior of the polyether ether ketone matrix at T > T _g provides a good intrinsic toughness to the material, and the bridging of translaminar crack by the glass fibers at the outer surfaces of laminates contribute to a moderate increase in its extrinsic toughness.