Efecto de la humedad ambiental en la resistencia y plasticidad de un compuesto de poliamida 6/66 reforzada con fibra de carbono corta fabricado por impresión 3D

Resumen

This study investigates the effect of ambient humidity on the mechanical behavior of a polyamide 6/66 (PA6/66) composite reinforced with short carbon fibers (CF) and fabricated by fused deposition modeling (FDM). The hygroscopic nature of polyamide promotes water absorption, altering the stiffness and ductility of the material. To evaluate this effect, specimens were conditioned for 48 h under: dry state (0% RH), exposure to 50% RH, 95% RH, and immersion in water. Tensile (ASTM D638) and flexural (ASTM D790) tests revealed a progressive reduction in mechanical properties with increasing moisture content. Tensile strength decreased by up to 60%, and flexural strength by up to 70% compared to the dry condition, while the elastic modulus and flexural modulus dropped from 1085 to 320 MPa and from 1409 to 320 MPa, respectively. Conversely, strain at break and fracture energy increased, indicating a more ductile behavior. The absorbed water acts as a plasticizer, disrupting hydrogen bonds between amide groups and reducing intermolecular cohesive energy. Nevertheless, the presence of short carbon fibers partially mitigates this deterioration by restricting chain mobility and maintaining a relatively high residual modulus. It is concluded that ambient humidity induces a balance between loss of stiffness and gain in toughness, a phenomenon of particular relevance for the design of structural and prosthetic components exposed to variable hygrothermal environments.