| We present a method for evaluating the damage in and failure of fiber reinforced composite materials. The method is based on dissipated energy and has three major components: (i) a relationship between the strain in the material and the magnitude of the dissipated energy density, (ii) a model that relates the dissipated energy density to matrix damage and fiber failure inside the material, and, accordingly, reduces the elastic properties of the material, and (iii) a nonlinear finite element code for calculating the strain at each point in the material taking into account the degradation of the stiffness as damage occurs. The method provides the parameters of interest, namely, the regions of matrix damage and fiber failure, the load-displacement curve, the failure load, and the failure displacement. Tensile, shear, and four point bend tests were performed with S-glass/epoxy solid coupons as well as with coupons containing a central hole. The load-displacement curves, failure loads, and failure displacements were measured and compared to the results computed by the method. The data and the results of the method are in good agreement. |
