Influence of a hydrogen/oxygen flame on the fire-behaviour and the tensile properties of hybrid Carbon Glass fibers reinforced PEEK composite laminates

This study investigates the residual tensile behaviour of hybrid Carbon Glass fibers reinforced thermoplastic PEEK laminates after they were exposed for 5 min to a hydrogen/oxygen flame. This flame results in a severe thermal aggression characterized by a wall temperature ranging from 900 to 1270 degrees C and with different heat fluxes (from 200 to 800 kW/m(2)). The thermally-induced damages were examined by means of microscopic observations and micro CT analyses. The results show that the mass loss linearly depends on the measured heat flux for a 5 min exposure. Depending on the fire testing conditions, the mechanical properties in tension (stiffness and strength) are totally degraded after exposure to the highest heat fluxes (600 and 800 kW/m(2)) but the retention of the tensile properties is moderate (about -35 to -60% decrease in strength and stiffness, respectively) after exposure to a 200 kW/m(2) heat flux. The residual tensile properties of CG/PEEK laminates follow master curves representing the correlations between the mass loss and the changes in the tensile properties regardless the heat flux. These master curves provide a relevant design rule for composite parts to be used under critical service conditions (H-2/O-2 flame exposure).