Tensile behavior of angle ply carbon reinforced PPS laminates under severe thermal aggressions: Homogeneous and heterogeneous temperature conditions

This study explores the effects of critical temperature conditions on carbon fiber-reinforced Poly Phenylene Sulfide (PPS) laminates, focusing on the coupling between thermal and mechanical behaviors. The thermo-mechanical behavior of angle-ply laminates is examined under both homogeneous (thermal decomposition and deformation/damage) and heterogeneous (fire) conditions following three primary objectives: (i) Investigate the impact of temperature distribution on the formation of porosities within the composite, considering their significance in thermal transfer and stress concentration-(ii) Evaluate the changes in residual mechanical behavior and properties under tension due to thermally-induced damage-(iii) Improve the understanding of the interactions between severe thermal exposures and the mechanical behavior. X-ray tomographic analyses and tensile tests were conducted to achieve these goals. Porosities resulting from thermal damage are identified as a key factor affecting the structural integrity of C/PPS laminates for high-temperature applications. Mechanical testing reveals that the porosity content significantly reduces the tensile properties (axial stiffness and strength). Under homogeneous temperature conditions, the decrease in the tensile properties is significant up to T-onset (465 degrees C) from which both the axial strength and stiffness dramatically decrease by -75 and -50%, respectively. As exposed to a kerosene flame during 60 s, corresponding to an aggression of 115 kW/m(2) on one face of the laminates, the retention of the residual tensile properties remains good (-12% and -22% in stiffness and strength respectively), despite the dramatic decomposition of the polymer matrix. This can be explained from the stress redistribution from the exposed to the back face, and from the role of thermal insulator played by porosities. Highlights<br /> Carbon fibers/PPS laminates were subjected to severe thermal aggressions<br /> The formation of thermally-induced porosities is studied<br /> A homogeneous aggression significantly decrease the tensile properties (-75%)<br /> Once the PPS matrix is severely decomposed, the load transfer is not possible<br /> After a 60 s flame exposure, the retention of tensile properties is good (-20%)