Deformation and fracture of a uniaxially reinforced composite material

The effects of fiber spacing on the mechanical response and fracture proper ties of a composite made of an epoxy resin and optical glass fibers have be en investigated. Two specimen types were tested: a notched specimen reinfor ced with one layer of equally spaced fibers (monolayer) under remote tensil e longitudinal loads and a specimen reinforced with several layers of equal ly spaced fibers (multilayer) in a compact-tension (CT) configuration. The experimental results indicate that in the monolayer specimens, the macrosco pic stress at the onset of non-linearity, sigma(c)(i) and fiber spacing, la mbda(x)., are related in the form sigma(c)(i) = K1 root lambda(x)(k(1) is a constant). The linear portion of the stress/strain curves scale with the r atio root lambda(x)/root B (B is the specimen width). In the multilayer spe cimens, an effective stress at the onset of non-linearity, sigma(A)(i), dep ends on the fiber spacing along the ligament direction, lambda(x),,, accord ing to sigma(A)(i) = sigma(Ao) + kappa(2)/root lambda(x) and (kappa(2) are sigma(Ao) constants). Approximating the layers of fibers with strips of eff ective material, two-dimensional simulations for an effective stress at cra ck initiation on the CT specimen are carried out by using a boundary-elemen t linear-elastic model. The results of the simulations support the trend of the experimental data. (C) 1999 Elsevier Science Ltd. All rights reserved.