Dynamic behaviour of precracked bimaterial structures applicable to wind propellers

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The proposal is motivated by the dynamic fracture process evaluation in layered composite materials (LCM) and structures, especially for bi-material structures. The intended analysis has application in engineering design and monitoring of knowledge based systems made of LCM (for instance thin coating on turbines and wind propellers), satisfying the increasing demand for high strength, high toughness, and questions connected with critical length of interface delamination, energetic conditions for change of a direction of a crack, critical mechanical loading for a full degradation of a structure, corrosion-resistance and wear-resistance properties and finally for lower failure rates during manufacturing and service processes. The main aim of the project is to develop and validate an analytical model proposed by the applicants Ivanova, Becker et al, (2010) for solving the dynamic interface cohesive behaviour and the delamination in a bi-material structure. The elastic-brittle interface behaviour has been already considered. In order to complete the problem, these investigations have to be continued and directed to cohesive interface behaviour and respective delamination. The application of the results obtained to turbines and wind propellers is one of the goals of the proposal. The analytical solution method is based on the modified dynamic Shear Lag method chosen to find the debond length along the interface and to predict the load-carrying capacity of a bi-material structure as a part of wind propellers. The Shear Lag method is very effective because of its simplicity (1D model). Its successful application in the static case has been proven by Ivanova et al (2009). Simulation studies will be proceeded in order to evaluate such important effects as: geometry of the bi-material structures, elastic and cohesive behaviour of the interface, frequency and amplitude influence of the external loading on debond length, as well as safety zones for the structure.