Simultaneous influence of strain rate and moisture on the anisotropic mechanical behavior of direct compounded compression molded PA6/Glass LFTs

Abstract

Fibre-reinforced polymer composites are an increasingly critical long-term solution for lightweighting the transportation sector, therefore, a comprehensive understanding of their mechanical behavior under varying environmental conditions and loading rates is critical. This study investigated the tensile properties and behavior of a direct-compounded compression-molded Polyamide6 (PA6)/glass long fibre thermoplastic (LFT-D) material, specifically examining the influence of moisture content and intermediate tensile loading rates, up to 150 s−1. This range is of significance to the transportation industry and is highly desirable for engineering design since data in the current literature is limited. Dried and undried samples were also examined at four distinct material orientations: 0°, +45°, ˗45°, and 90°. The results confirmed that moisture presence significantly altered the mechanical properties of PA6/Glass LFT material under quasi-static loading rates; in contrast, its effects were negligible under dynamic loadings. Notably, the material exhibited significant strain rate sensitivity within the range of 0.0001 s−1 to 150 s−1. In the 0° material direction, with higher fibre orientation distribution, the undried materials demonstrated a substantial increase of 93% in Young's modulus and 172% in ultimate tensile strength while the complementary dried samples displayed increases of 76% and 97%, respectively. Tensile strength reached 293.8 MPa and 276.7 MPa for undried and dried samples, respectively, in this particular material direction. However, the strain at failure remained consistent at approximately 4% for undried samples and 3% for dried samples, resulting in an increase in tensile toughness by 292% (up to 6.9 MPa) for undried samples and 114% (up to 4.7 MPa) for dried samples.