Experimental Investigation on the Structural Integrity of High‐Performance Thermo‐Plastic Polymer Composites Exposed to Cryogenic Environments

ABSTRACT This research highlights the evaluation of high‐performance thermo‐plastic polymer composites for cryogenic applications. In this investigation, the composite is made by poly ether‐ether‐ ketone (PEEK) with various fibers such as para‐aramid fiber, E‐Glass, and carbon (T‐300). The surface of each fiber and PEEK film modified using low‐pressure nitrogen plasma treatment. These three fiber composites were fabricated using compression molding techniques at 380°C and 2 bars of pressure, with a holding time of 1 h. These fabricated composites were tested without and with cryogenic exposure (5 days exposure of liquid nitrogen, LN 2 ) to evaluate the mechanical characteristics. The para‐aramid fiber composite loses only about 10% and 3% of its ultimate tensile strength and modules of toughness when exposed to non‐exposure and cryogenic conditions, respectively. Compared to other fiber composites, the para‐aramid fiber composite has a very low modulus toughness degradation under cryogenic exposure. The composites were characterized by various analytical methods, including the scanning electron microscopy (SEM), X‐ray diffraction (XRD), limited oxygen index (LOI), and thermal conductivity. The limiting oxygen index (LOI) of para‐aramid fiber composite demonstrates good fire resistance potential. X‐ray diffraction (X‐RD) analysis reveals that the plasma‐treated para‐aramid fiber composite has a more crystalline molecular structure compared to the untreated para‐aramid fiber composite. Differential scanning calorimetry analysis (DSC) and Thermogravimetric analysis (TGA) of a para‐aramid fiber were performed to evaluate the optimal processing temperature for the fabrication process, the reaction type (endothermic reaction), and to the Glass transition temperature (T g ) for the composite, respectively.