Lightweight carbon nanotube surface thermal shielding for carbon fiber/bismaleimide composites

Abstract

Carbon fiber reinforced polymers (CFRP) are becoming increasingly used in aerospace applications which require lightweight and stability at high temperatures. This paper discusses a systematic design of a carbon nanotube/phenolic thermal protection layer (TPL) with heat shield functionality while maintaining designed mechanical strength compared to traditional CFRP composites. These TPLs were integrated onto the surface of carbon fiber/bismaleimide composites to act as a heat shield for hybrid composites. A bonding layer of ultra-thin unidirectional carbon fiber was introduced between the TPLs and CFRP to improve the constituent interface. Hybrid composites with different TPL volume fractions were produced. The TPLs resulted in a 17% decrease of the through-thickness thermal conductivity for hybrid composites. A flame torch test was used to evaluate the thermal shield effectiveness, and the hybrid composites showed a noticeable increase in residual flexural strength and modulus when compared to the control samples under a heat flux of 20 W/cm2. The retention of the strength and modulus of the hybrid composites after burning was 39% and 70% of the initial value, respectively, as compared to 11% and 21% of the CFRP control. This paper also discusses the effects of TPLs’ coefficient of thermal expansion and protection mechanisms.