TEMPERATURE-DEPENDENCE OF IMPACT FRACTURE ENERGIES OF SHORT GLASS FIBER-EPOXY AND UNSATURATED POLYESTER COMPOSITES

The temperature dependence of the impact fracture energies of composites reinforced with random‐planar orientation of short fibers was studied theoretically and experimentally. The theoretical values of the impact fracture energy of these composites is described by the sum of the fracture energy of the matrix and the fibers and the energy necessary to pull out the fibers on the crack surface, taking into consideration the temperature dependence of the critical fiber length and the breaking probability of fibers. The impact fracture energies were studied experimentally for epoxy and unsaturated polyester resins reinforced with random‐planar orientation of short glass fibers. The theoretical values of the impact fracture energy were in good agreement with the experimental values. It was found that in any composite, the impact fracture energy of the fibers in a composite mainly contributes to the impact fracture energy of the composite at room temperature. At higher temperatures, fiber pull‐out energy is more significant. Copyright © 1979 John Wiley & Sons, Inc.