The Effect of Fibre Orientation on the Density and Tensile Properties of Basalt Fibre/Epoxy Composites

The mechanical behaviour of fibre-reinforced epoxy composites is strongly influenced by the orientation of reinforcing fibres within the epoxy matrix. Understanding the relationship between fibre orientation, void formation, density, and mechanical properties in fibre-reinforced polymer (FRP) composites is crucial for optimizing their performance. Basalt fibres, known for their superior properties, were integrated into epoxy resin to create composite materials with varied fibre orientations via the hand lay-up method. The composites were fabricated into oneply ((0/90) and (±45)), two-plies (0/90)(±45)) and three-plies ((0/90)(±45)(0/90) and (±45)(0/90)(±45). The addition of basalt fibres increased the composite density, owing to the inherently denser nature of basalt compared to epoxy. When the number of basalt fibre plies is increased to two and three, the density of the composites decreases due to the presence of voids and the trapping of air between the layers of fibres during the process of layering and impregnation. One-ply composites with (0/90) orientation exhibited higher tensile strength and Young's modulus due to fibre alignment with the loading axis, enhancing load resistance. Conversely, (±45) orientation resulted in higher tensile strain, promoting deformation and load distribution in shear. Tensile strength and Young's modulus of two plies of basalt fibre composites lie between those of one-ply composites with (0/90) and (±45) orientations since the (0/90) fibres efficiently resist the applied load along their aligned directions, while the (±45) fibres aid in distributing and absorbing the load in shear, which enhances overall tensile strength and modulus compared to one-ply (±45) composites. In the case of three-plies composites, the composites with two plies oriented in (0,90) demonstrated higher tensile strength and Young's modulus when compared to those with two plies of fibres oriented in (±45).