Influence of temperature degradation on the low velocity impact behavior of hybrid thermoplastic PEEK laminates

Abstract

To evaluate the severity of thermal degradation on the impact response of carbon (C) and glass (G) fibers reinforced PolyEther Ether Ketone (PEEK) laminates, low velocity impact tests were conducted at a temperature higher than the glass transition temperature Tg (150°C) and after exposure to a kerosene flame (5-10-15′). The first important effect resulting from temperature increase was a reduction of the impact energy required to induce BVID (Barely Visible Impact Damage). The second effect was that matrix ductility (enhanced at T>Tg) contributes to significantly modify the permanent indentation. Not surprisingly, the plastic and viscoplastic deformation mechanisms being ruled by the PEEK matrix behavior at high temperature, the permanent indentation increases by almost 40% for all impact energies. Contrary to the external damage represented by permanent indentation, temperature has a tremendous influence on the internal damage as there was virtually no delamination in the CG/PEEK laminates impacted at Room Temperature (RT) and 150°C. At last, impact tests conducted on specimens exposed to a kerosene flame implied that the impact bearing capabilities of CG/PEEK laminates dramatically decreased after a 5′ exposure and became even critical after 10′ as perforation was observed. For 40 J impacts, the permanent indentation was multiplied by 3–9 with respect to the as-received specimens.