Damage evolution in laminates with manufacturing defects

Sammanfattning: In this thesis, experimental investigations and theoretical studies on the stochastic matrix cracking evolution under static loading in composite laminates with manufacturing defects are presented. The presented work demonstrates a methodology that accounts for the statistically distributed defects in damage mechanics models for the assessment of the integrity of composites and for the structural design of composites.The experimental study deals with the mechanisms of the stochastic process for the multiplication of cracks in laminates. The defects introduced by the manufacturing processes are found to have significant effect on the matrix cracking evolution. Influenced by the distributed defects, the initiation and multiplication of cracks evolve in a stochastic way.Based on the experimental investigations, a statistical model for the matrix cracking evolution is developed. Simulations based on the model yield accurate predictions compared to the experimental data. The parameters of the assumed Weibull distribution of the static strength are estimated from the experimental crack density data. The estimated Weibull distribution provides an efficient basis to characterize the manufacturing quality of composite laminates. Compared to deterministic approaches, this approach provides comprehensive information on the strength property of composite laminates.