Effect of Reinforcement Alignment to the Properties of Polymer Matrix Composite

Numerous applications have been proposed and demonstrated for producing align-fiber
composite. However, none had stated a right procedure to align the fiber to optimize the
properties of polymer matrix composite (PMC) such as its strength and water absorption
property. Therefore, the aim of this study is to determine the best alignment of
reinforcement material in order to optimize the properties of PMC in its application. In
this study, woven roving fiberglass was used as the fiber and unsaturated polyester resin
as its matrix material. Hand lay-up process was used to fabricate the laminated
composite. The specimens were divided into four major categories with different
alignment and thickness of fiber and matrix which were 5 layers bidirectional, 5 layers
multidirectional, 7 layers bidirectional, and 7 layers multidirectional. Tensile test
showed that bidirectional alignment was better in term of mechanical properties
compared to multidirectional alignment. The 5 layers bidirectional have a higher tensile
strength compared to 5 layers multidirectional. While 7 layers bidirectional have a
higher tensile strength compared to 7 layers multidirectional. The modulus of elasticity
of bidirectional alignment was higher than multidirectional alignment. Bidirectional
alignment was better because the external tensile load was equally distributed on all the
fibers and transmitted along the axis of the fibers. Whereas in case of multidirectional
alignment, fiber axes was non-parallel to load axis, resulting in off axis pulling of fibers
and increased stress concentration causing the earlier failure of laminates. Water
absorption test showed that multidirectional alignment absorbs more quantity of water
compared to bidirectional alignment. Therefore, multidirectional alignment was not
suitable for underwater application such as boat, canoe and yacht. It can be concluded
that, the properties of PMC depending on the alignment of reinforcement material.