On the mixed mode I/II/III inter-laminar fracture toughness of cotton/epoxy laminated composites

Nowadays, natural fiber reinforced laminated composites have been extensively used in order to fabricate the various structures. In this paper, a woven cotton/epoxy laminated composites system was considered. The main purpose of this investigation is to measure a full range of mixed mode I/II/III Inter-laminar facture toughness (IFT), critical strain energy release rate (CSERR) and the mechanical properties of this material. Hence, in addition to tensile, flexural and in-plane shear tests, a series of delamination tests consisting of pure modes, mixed modes I/II, I/III and II/III were carried out. The fracture tests were conducted using a modified Arcan fixture and an out-of-plane fixture. The experimental results showed that the delamination responses of cotton/epoxy system are deeply dependent on the loading conditions. It was also found that the Inter-laminar fracture toughness and CSERR under pure mode I and mixed mode II/III loading conditions have the lowest and greatest values among the delamination modes, respectively. It was also conducted that in comparison with the woven carbon/epoxy and glass/epoxy systems, the modes I, II and III CSERR of cotton/epoxy is remarkable.