Tensile properties of novel carbon/glass hybrid thermoplastic composite rods under static and fatigue loading

Abstract

Novel carbon/glass hybrid thermoplastic composite rods have been developed consisting of a PAN-based carbon fiber, an E-glass fiber, and a thermoplastic matrix. Three types of hybrid rods with different carbon/glass ratios were then fabricated. The surface and cross-sectional morphologies of the hybrid rods were observed using a digital microscope. Additionally, the volume fractions of carbon/glass fibers, matrix, and void were determined by specific gravity measurements and thermogravimetric analyzes. The glass fibers in the hybrid rods display a braided structure of the 2/2 twill weave. The braid angle (defined as the orientation angle of the interlacing yarns with respect to the longitudinal axis of the rod) ranged from 22.3° to 35.2°. The various volume fractions were in the ranges of 24.6-46.2% for the carbon fiber, 23.2-39.8% for the glass fiber, 23.4-25.5% for the matrix, and 7.3-10.2% for the voids. The tensile properties and fracture behavior of the hybrid rods under static and fatigue loading were also investigated. For the static tests, the stress applied to the specimen was nearly linearly proportional to the strain until the failure of all-hybrid rods. The tensile modulus, strength, and failure strain of the hybrid rods were measured in the ranges of 65-91GPa, 1.42-1.84 GPa, and 2.1-2.2%, respectively. The tensile modulus and strength increased as the volume fraction of the carbon fiber increased. However, the failure strain decreased as the volume fraction of the carbon fiber increased. For fatigue tests, the maximum applied stress-number of cycles to failure (S-N) curves for all-hybrid rods were obtained from 0.1 of the stress ratio (minimum/maximum stress) and 10 Hz of the loading frequency. The fatigue strength at 107 cycles for all-hybrid rods was less than 30% of ultimate breaking stress. The fatigue performance of the hybrid rods was significantly lower than that of conventional carbon fiber reinforced polymer matrix composites and steel rods. The voids in the hybrid rods affected the fatigue tensile properties.