Impact of moisture and temperature on the flexural properties of 3D-printed carbon fiber-reinforced polyamide composites

Abstract

This study examines the flexural properties of 3D-printed composites reinforced with short and continuous carbon fibers in a polyamide (PA) matrix before and after conditioning at 22°C/90% relative humidity. Flexural tests were performed on as-printed “dry” and conditioned “wet” samples at temperatures of 22–50°C. The materials tested were Onyx (PA with short carbon fiber reinforcement), Onyx + cCF (Onyx reinforced with continuous carbon fibers), and ULTEM 9085 (polyetherimide blend), a moisture and temperature resistant thermoplastic. Results showed that Onyx and Onyx + cCF were significantly affected by both moisture and temperature. At room temperature, Onyx dry exhibited 18% and 15% greater flexural modulus and strength, respectively, than Onyx wet, but the properties of Onyx dry decreased more rapidly than Onyx wet with increasing temperature, leading to a 68% and 29% greater flexural modulus and strength, respectively, for Onyx wet at 50°C. Onyx + cCF absorbed the greatest amount of moisture, leading to the greatest rate of decrease in flexural modulus and strength with increasing temperature. These results demonstrate the need to more thoroughly characterize the effects of moisture and temperature on the mechanical properties of 3D printed PA composites to understand their performance in applications requiring environmental exposure.