The goal of the project is to develop an efficient method for prediction and analyzing accurately and realistically dynamic fracture of sandwich materials with damaged skin-to-core interface under real-life dynamic working conditions. To achieve this aim the following items are suggested to be realized within the project:
- Elaborating a model of sandwich panels, which involves dynamic crack propagation taking into account material anisotropy of the constitutive material layers, contact/separation conditions and friction effects within the debonded region and taking into account of inertial effects around the crack tip stress field;
- Developing techniques for determining micro-scale interfacial fracture parameters such as dynamic interfacial strength and interfacial toughness via fracture testing of the skin-to-core sandwich interface;
- Implementing the developed mathematical model and obtained fracture data into the finite element model to carry out finite element simulations for examining mechanical behavior and fracture of sandwich panels in dynamic environment.
A combination of analytical, numerical and experimental techniques focused on dynamically loaded sandwich structures is the methodology to fulfill the project objectives. In this regard, the following research techniques are involved:
- Analytical and semi-analytical approaches based on the asymptotic stress field in a bi-material interface within the two-dimensional elasto-dynamic crack model is applied for a better understanding of failure mechanisms in the skin-to-core interface of two-dimensional sandwich panels;
- A finite element formulation based on a variational statement is used for modelling a three-dimensional elasto- and viscoelastic-dynamic problem in sandwich panels taking into account dynamic crack propagation. Herewith large displacements, material anisotropy, material rate dependence, contact/separation conditions and friction between crack edges and appropriate mixed-mode fracture criteria for crack onset and growth are going to be implemented into the standard Galerkin formulation;
- Experimental testing sandwich specimens in mode I, II, and mixed-mode I/II dynamic loading is performed to create fracture failure envelopes for these modes to use them in FE simulations of debonded sandwich panels;
- A finite element modelling idealized sandwich structures such as beams, plates and shells containing a damaged skin-to-core interface under dynamic loading is carried out using the ABAQUS code to simulate their overall dynamic response and dynamic fracture;
- A comparative analyzing dynamic fracture of sandwich panels simulated by ABAQUS models and observed with the ARAMIS system for real sandwich models is fulfilled to estimate the efficiency and accuracy of the proposed prediction method.