Empirical model for stress ratio effect on fatigue delamination growth rate in composite laminates
An empirical model is proposed for the stress ratio effect on the fatigue delamination growth rate in composite laminates under single-mode loading, intending to provide a simple and accurate description tool in engineering application. The model is based on heuristic considerations of damage accumulation ahead of the crack. Linear cumulative assumption is used for damage estimation. Comparison of the prediction based on the proposed model with the test results for different carbon, glass, and alumina fibre-reinforced composites at several stress ratios shows reasonable agreement.
Glass fibre strength distribution determined by common experimental methods
The tensile strength of brittle fibres is routinely described by the Weibull distribution. The parameters of the distribution can be obtained from tests on single fibres and fibre bundles or from model composite tests. However, there is growing evidence that the distribution parameters obtained by different experimental techniques differ systematically. In order to investigate the possible causes of such discrepancies, single-fibre tension, fibre bundle, and single-fibre fragmentation tests are employed in this study to obtain strength distribution of commercial E-glass fibres. The results reveal parameter dependence on the approach used to extract the distribution parameters from experimen…
Fibre fragment distribution in a single-fibre composite tension test
Abstract Single fibre fragmentation tests are performed for brittle fibres with Weibull strength distribution and different surface treatments. The fragmentation process is modelled and closed-form expressions for break spacing distribution are obtained. The model accounts for the effect of finite fibre length on the initial fragmentation as well as for break interaction on the advanced fragmentation stage. It is assumed that the exclusion zone due to fibre–matrix interface failure and stress recovery in the fibre is linearly dependent on the applied load. This assumption is validated experimentally. The derived theoretical average fragment length dependence on applied load is used to deter…
Model of delamination propagation in brittle-matrix composites under cyclic loading
A model of interlaminar fatigue crack growth based on damage accumulation ahead of the crack is proposed. Linear cumulative assumption is used for damage estimation, and a quadratic failure criterion is applied for complex interlaminar loading. Model parameters are determined from mode I and mode II fatigue tests, and used to predict mixed-mode delamination propagation rate. Comparison of theoretical prediction with mixed-mode test results for different brittle graphite FRP at several mode- and load ratios show reasonable agreement.