Effect of Reinforcement Alignment on the Properties of Polymer Matrix Composite

Abstract

Numerous applications have been proposed and demonstrated for aligned-fiber composites. However, none had stated a correct procedure for aligning the fibers to optimize the properties of the polymer matrix composite (PMC), such as its strength and water absorption properties. Therefore, the aim of this study is to determine the best alignment of reinforcement material in order to optimize the properties of PMC. Woven roving fiberglass was used as the fiber and unsaturated polyester resin as its matrix material. A hand lay-up process was used to fabricate the laminated composite. The specimens were divided into four major categories with different alignments and thicknesses of fiber and matrix, which were five-layer bidirectional, five-layer multidirectional, seven-layer bidirectional, and seven-layer multidirectional. Tensile tests showed that bidirectional alignment offered better mechanical properties compared with the multidirectional alignment. The five-layer bidirectional arrangement has a higher tensile strength compared with five-layer multidirectional arrangement. The seven-layer bidirectional arrangement has higher tensile strength compared with the seven-layer multidirectional arrangement. The modulus of elasticity of the bidirectional alignment was higher than that of the multidirectional alignment. Bidirectional alignment was better because the external tensile load was distributed equally on all the fibers and transmitted along the axes of the fibers. Whereas in the case of multidirectional alignment, the fiber axes were non-parallel to the load axis, resulting in off-axis pulling on the fibers and increased stress concentration, which caused earlier failure of the laminates. Water absorption tests showed that the multidirectional alignment absorbs a greater quantity of water compared with the bidirectional alignment. Therefore, the multidirectional alignment was shown unsuitable for underwater applications, such as boats, canoes, and yachts. It can be concluded that the properties of PMC depend on the alignment of the reinforcement material.