Review of delamination predictive methods for low speed impact of composite laminates

Predicting the damage tolerance of laminated composite aircraft components subjected to low velocity impact events, such as runway debris or hail, is providing a significant challenge to the current methods. This paper reviews the current damage mechanics and fracture methods for predicting delamination under impact available in the literature. Many damage mechanics models are available, some providing good delamination predictions. The linear elastic fracture mechanics method has been used extensively where the shape of the delamination front can be predicted and a suitably shaped mesh can be provided. However, as impact events produce irregular shaped delamination fronts, this method requires an adaptive mesh approach that is not yet available in any of the major analysis codes. The cohesive fracture model solves some of the limitation of the linear elastic fracture mechanics method, however a definitive study of its abilities has yet to be found in the literature. The delamination threshold load method is an extremely simple method and provides surprisingly good results. The review concludes that additional development of current techniques is required before a definitive predictive delamination method will be available.