Statistical Approach to Delamination Onset Prediction

摘要

Weibull statistical scaling of strength as a function of volume was used to predict free edge delamination onset in AS4/3501-6 laminates. Besides the Weibull integral method, Critical Weibull Volume (CWV) method was applied allowing one to identify the location of the failure onset, which in all cases occurred at the midsurface. The distribution of the transverse strength as a function of volume, which is required in the present method, is obtained in a separate set of testing involving 90° specimens. Thus the onset of delamination prediction is performed without the use of any empirical parameters, such as characteristic and/or average length. The delamination onset loads were predicted for a family of [θ/-θ/θ/-θ/θ0]_s laminates for θ=15,20,25 and 40, which were experimentally studied in [1]. B-spline analysis method was used for 3-D stress prediction to calculate the transverse normal stress distribution used for delamination onset prediction. It was shown that the delamination onset loads for θ=15 laminates, which were predicted based only on mechanical stresses contributions were up to 30% higher than that by taking into account the thermal residual stresses. The predicted probability of delamination onset at a given load was very close to that obtained experimentally in [1] for all laminates when the thermal residual stress was taken into account.