Abstract

This work concerns the stochastic mechanics and reliability of composite laminates. The reliability of notched composite laminates is evaluated based on the average stress over a certain characteristic distance from the notch edge and the strength of the corresponding un-notched laminate. In the present work the perturbation in the radius of the hole is modeled using a hypotrochoid variation and further, the location of the hole centre is modeled using a Gaussian random variable. In order to achieve a design with a required reliability and safety, (i) the stress analysis of the notched laminate has to be conducted based on a stochastic approach, (ii) the strength distribution and its probabilistic parameters have to be determined based on a number of tests, and (iii) the reliability analysis has to be conducted. Two-dimensional stochastic finite element analyses of notched symmetric cross-ply [0/90] 4 s and angle-ply [02/±45] 2 s composite laminates are conducted. A comprehensive experimental investigation is carried out to determine the strength values of the laminates subjected to tensile load. Average stress criterion is used to predict the characteristic length values of the laminates. The distributions of the strength and characteristic length of laminates with symmetric cross-ply [0/90] 4 s configuration are determined by testing 25 samples of notched and 25 samples of un-notched laminates. In a similar manner, tests on angle-ply laminate [02/±45] 2 s are conducted. Stochastic simulation is performed on the laminates by subjecting them to uniaxial, biaxial, shear and bending loads. Probabilistic moments of the stress parameters that are of interest are found out for the so-called controlled hole and uncontrolled hole laminates. The reliability indices for the two laminate configurations are calculated by combining the stochastic finite element analysis and the test results.