EXPERIMENTAL AND NUMERICAL-STUDIES IN MODEL COMPOSITES .2. NUMERICAL RESULTS

A numerical approach using the boundary element method for strength an d toughness of a composite with long aligned fibers is reported. The t hree-dimensional problem is reduced to a two-dimensional one by substi tuting the rows of fibers with layers of appropriate width and elastic constants. The configuration examined in this work is a compact tensi on specimen similar to that used in the experimental studies (Part I, [1]). The experimental results on strength and apparent fracture tough ness are compared with the numerical results. For the particular geome try and fiber spacing, the numerical simulations are in good agreement with the experimental findings, i.e. the composite's strength sigma(A ), scales with the fiber spacing lambda, in the form of sigma(A)=kappa /root lambda. Using the numerical formalism a number of different geom etries was examined. The simulations suggested that if the external sp ecimen characteristics remain the same and the fiber spacing in the di rection of crack advance is changed, then the strength of the composit e specimen can be expressed sigma(A)=sigma(Ao)+kappa/root lambda(x). I f the fiber spacing varies in both directions simultaneously, for a ce rtain range of lambda, it can be considered that the composite's stren gth sigma(A), is proportional to 1/root lambda.