Investigation on the Tensile Properties of Knitted Fabric Reinforced Composites made from GF-PP Commingled Yarn Preforms with Different Loop Densities

The influence of the loop density of rib 1: 1 fabric preform made from GF-PP commingled yarn on the tensile properties of the composites is investigated. Six samples of rib 1: 1 fabric preform with different loop densities are studied. It has been found that the tensile strength of composites show an increase followed by a light decrease as the loop density of the rib 1: 1 fabric preform increases, while the fracture strain just presented a contrary variation tendency. Fiber strength efficiency (FSE) is introduced to explain this phenomenon. Also, the inherent characteristic of loop structure, the homogeneity of fiber-matrix distribution in composites, and the continuousness of the reinforcement are taken into consideration to explain this.