Investigation of behaviors of glass/epoxy laminate composites reinforced with carbon nanotubes under quasi-static punch shear loading

Abstract

In this paper, in addition to investigation of the effects of adding of nanotubes on the tensile properties of epoxy matrix and glass/epoxy laminate composite, the effects of adding of nanotubes and the effect of indenter shape on quasi-static punch shear properties of glass/epoxy laminate are experimentally studied. Laminate nanocomposites have 12 layers of plain weave glass fibers which are made by hand lay-up method. Resin is composed of a two-component epoxy; Epon 828 as the base and Epikure F-205 as the curing agent. Multi-walled carbon nanotubes modified by hydroxid (–COOH) are used with 0%, 0.5% and 1% ratio in weight with respect to the matrix. In quasi-static punch shear tests, three indenters (flat, conical and ogival) are utilized. Tensile test results for nanomatrix show that the most changes are obtained on 0.5 wt.% specimen, in which the ultimate strength and strain energy are increased 22% and 17% respect to the neat sample, respectively. No distinct change was observed in tensile behavior of the hybrid composite samples by the addition of carbon nanotubes. Punch shear test results show that addition of carbon nanotubes reduces the contact force and the absorbed energy in ogival and conical indenters. In presence of nanotube particles, the maximum decreasing in the contact force and the absorbed energy happens in conical nose indenter with 23% and 26% decrease, respectively. Comparison of different indenters shows that in the neat samples, the maximum and minimum contact force belongs to the flat nose indenter (2.45 kN) and the ogival nose indenter (0.75 kN), respectively, while the maximum and minimum absorbed energy belongs to the conical nose indenter (13.5 J) and the flat nose indenter (10 J), respectively. Moreover, change of indenter geometry changes the failure mechanism, so that the failure of flat indenter is plugging and failure of sharp indenter is petaling.