Effects of Pre-stretching on the Tensile Properties of Knitted Glass Fiber Fabric Reinforced Polypropylene Composite

摘要

Weft knitted glass fiber(GF)fabric reinforced polypropylene(PP)composite sheets were fabricated by hot pressing of stacked rib 1:1 knitted fabric preform layers.The knitted preforms were made from GF/PP commingled yarn containing 50 vol%(approx=73 wt%)GF.Before hot pressing,the preforms were stretched in the wale direction at various ratios.The tensile properties of the pre-stretched GF-PP composites were studied.It was found that there is a critical value of pre-stretch ratio as far as tensile stiffness and tensile strength are Concerned.On increasing the pre-stretch ratio within the range of this critical value,both tensile stiffness and tensile strength increase.If the pre-stretch ratio goes beyond this critical value and continues to increase,both tensile stiffness and tensile strength display a tendency of slight decrease because of the break of more glass fibers.The failure strain of the composites decreases with the increase of the pre-stretch ratio because of the decrease of the stretchability of the knitted reinforcements.