جستجوی مقالات مرتبط با کلیدواژه "indenter geometry" در نشریات گروه "مکانیک"

In this paper, the effects of the adding of carbon nanotubes on quasi-static punch shear behavior of glass/epoxy laminated composites under penetration of three different indenters has been investigated experimentally. The hybrid laminate nanocomposites have 12 layers is manufactured by Hand lay-up method. Fibers have a plain-weave configuration with density of 200 g/m2, while the epoxy resin system is made of diglycidyl ether of bisphenol A resin (DGEBA), Epon 828, with Epikure F-205 as the curing agent. The multi-walled carbon nanotubes (MWCNTs) modified with hydroxide (-COOH) are dispersed into the epoxy system in a 0% and 1% ratio in weight with respect to the matrix. In order to study of influence of the nose shape, three different indenters, flat, conical and ogival, were used. Moreover, the tensile test was performed on the nanomatrix and the hybrid laminate nanocomposite samples. The tensile test indicated that the addition of nanotubes on the tensile properties of resin were seen a significant increase, but no significant changes were observed in the tensile properties of the hybrid laminate nanocomposites. Results of the quasi-static punch shear test show that the highest contact force is exhibited by flat indenter, while the highest absorbed energy is shown by conical indenter. Totally, the adding of carbon nanotubes reduces the contact force and absorbed energy.

This paper, experimentally evaluates the effects of indenter geometry on quasi-static perforation process of laminated woven glass epoxy composites. Low loading rate tests were performed, using six indenters with blunt, hemispherical, conical (cone angle of 37˚ and 90˚) and ogival (caliber radius head of 1.5 and 2.5) nose shapes. Composite behaviors like energy absorption, contact force, failure mechanisms and friction force were investigated for different indenter shapes. Hand lay-up method has been used to manufacture composite targets with 18 layers of 2D woven glass fibers of 45% fiber volume fraction. The epoxy system is made of epon 828 resin with jeffamine D400 as the curing agent. The results show that the load displacement curve is divided to five areas. Some of these areas may have higher or lower magnitude, depending on indenter nose shape. The highest contact force is exhibited by unsharpened indenter. The lowest contact force and so the best performance is seen in ogival (CRH=2.5) indenter. Comparing absorbed energies shows that for an identical dent depth, the amount of absorbed energy is major for unsharpened indenters. The 37˚ conical indenter needs the highest energy for perforation, which is 2.6 times more than blunt indenter’s.