Durability study of thermoplastic pultruded composites based on polyamide

• Long-term hygrothermal durability of pultruded GFRPA and BFRPA composites was assessed. • Basalt fiber composites showed superior retention of flexural and ILSS values. • Moisture absorption followed Fickian behavior, with temperature dependence. • Alkaline exposure caused significant mechanical degradation, especially in GFRPA. • BFRPA composites demonstrated enhanced chemical resistance and dimensional stability. This study investigates the long-term durability of polyamide (PA) based pultruded thermoplastic composites reinforced with basalt and glass fibers. Composite profiles were manufactured by pultrusion and subjected to hydrothermal aging in distilled water and in alkaline solutions for up to 120 days at temperatures of 20°C and 40°C. Mechanical properties were evaluated by way of flexural strength and interlaminar shear strength (ILSS) testing. Moisture absorption was evaluated using a Fickian model. Initial testing revealed superior mechanical performance of basalt fiber reinforced polyamide (BFRPA) composite, with flexural strength and ILSS values reaching 518 MPa and 40.2 MPa, respectively, compared to 385 MPa and 28.3 MPa for glass fiber reinforced polyamide (GFRPA). Following extended immersion in alkaline solution at 40°C, the flexural strength of BFRPA was maintained at 164 MPa, corresponding to nearly 32 % of its original value (518 MPa), while that of GFRPA declined to 136 MPa, equivalent to about 35 % of its initial 385 MPa. Basalt fiber reinforced polyamide composite absorbed water faster but retained less moisture at equilibrium, likely due to its porous structure and presence of stable oxides improving its chemical resistance in adverse environments. These results demonstrate superior durability of basalt fiber reinforced polyamide composites in chemically aggressive environments and attest to their suitability for long-term structural applications in marine, civil, and industrial sectors.