Stiffness loss of laminates with aligned intralaminar cracks Part II. Comparisons

Abstract

The effective models (h₀, l₀) and (h₀, l) [7] describing reduction of the in-plane effective moduli of the [0°_m /90°_n]_s cross-ply composites cracked in the internal layer and subjected to in-plane boundary forces are applied to the description of the degradation of the effective Young, Kirchhoff and Poisson moduli of the [0° /90°]_s and [0° /90₃]_s glass/epoxy and [0° /90₂]_s graphite/epoxy laminates. lt is shown that the graphs of E₁(c_d) (c_d represents crack density) lie slightly above the Hashin's curves, while G₁₂(c_d) predictions coincide with the curves of Hashin. Evaluation of the off-diagonal terms, i.e. ν₁₂(c_d), ν₁₂ (c_d) are incorporated in the algorithm. In all comparisons with the experimental results of Groves, Ogin, Highsmith and Reifsnider the predictions of E₁(c_d) according to the model (h₀, l) provide lower bounds, slightly better than the bounds of Hashin. Some predictions of the model (h₀, l) are proved to be similar to McCartney's "generalized-plane-strain" results.