Flexural and fracture behavior of natural fiber knitted fabric reinforced composites

Decreasing natural resources and increasing environmental destructions dispatch researchers to find more ecological solutions in material industry. Natural fibers have recently become an interesting topic as an alternative reinforcement material for fiber reinforced polymer composites for researchers. In this study; the effect of knitting density, natural fiber type, crack length, and fabric direction (wale or course) on the fracture strength and fracture toughness of laminated composites reinforced with natural fiber knitted fabric were investigated. For this aim, plain fabrics made of 50/50 bamboo/cotton, 50/50 viscose/cotton, and 50/50 modal/cotton blended yarns were knitted with three different knitting density. After that; bamboo/epoxy, viscose/epoxy, and modal/epoxy laminated composites were produced by using hand lay-up method. Quasi-static three-point bending tests have been carried out on the single-edge notched bending composite specimens, which have a crack in wale or course directions. Fractured surfaces investigated through the Scanning Electron Microscopy describing different failure mechanisms are also reported. Test results showed that fabric which knitted in cellulosic fibers, reinforced composites, had higher flexural strength and fracture toughness in the wale direction. It has also been observed that the knitting density and crack geometry affect the crack propagation behavior. POLYM. COMPOS., 40:217–228, 2019. © 2017 Society of Plastics Engineers. © 2017 Society of Plastics Engineer