Influence of Fiber Orientation on the Tensile Performance of Neat and Halloysite Nanotube-Modified Glass Fiber-Reinforced Epoxy Laminates

Abstract

Fiber orientation plays a fundamental role in governing the load transfer efficiency and failure behavior of fiber-reinforced polymer composites, while nanoscale reinforcement offers an effective strategy for tailoring their mechanical response. In this study, the influence of fiber orientation on the tensile performance of neat and halloysite nanotube (HNT)-modified glass fiber-reinforced epoxy (GFRE) laminates was investigated. Bidirectional plain-woven E-glass/epoxy laminates were fabricated, and tensile specimens were machined at orientations of 0°, 15°, 30°, and 45°, with the orientation angle defined relative to a principal yarn direction of the woven reinforcement. The tensile response was evaluated in terms of ultimate tensile strength, elastic modulus, failure strain, and modulus of toughness. The results revealed that fiber orientation influenced the tensile response, with tensile strength decreasing from 136.80 MPa at 0° to 49.67 MPa at 45° for neat laminates. HNT modification increased the tensile strength by 20.13%, 22.77%, and 6.70% at fiber orientations of 0°, 15°, and 30°, respectively, whereas a 6.72% reduction was observed at 45°. The elastic modulus exhibited the greatest enhancement at 0°, increasing by 66.32%, while progressive reductions were observed with increasing off-axis orientation following HNT modification. The failure strain decreased by 20.27% at 0° but increased by 8.48% at 15°, while minor changes occurred at 30° and 45°. The modulus of toughness exhibited its greatest HNT-induced improvement at 15°, increasing by 22.06%, while slight reductions occurred at 0° and 30° and a more pronounced reduction at 45°.