Multi-Scale Modelling of the Nonlinear Deformation and Damage Behavior of Fiber Reinforced Composites


Composite materials are formed by a combination of two or more materials to achieve properties that are superior to those of its constituents. They consist mainly of unidirectional fibers or textile fabrics which are embedded in a matrix material. Due to their weight saving capabilities, they have become increasingly important for the automotive and aerospace industry. Depending on the application, there are a variety of fibre/matrix combinations. Besides the anisotropic structure, the stress-strain response of these materials can be highly nonlinear for fibres that behave as an elastoplastic material. Modelling such a material requires the consideration of different length scales in order to capture the intrinsic microstructure of the composite material in the structure computation on the macro-level. To accomplish this, the aim is to develop an anisotropic continuum phenomenological material model which takes into account the microscopic response of the individual constituents.

The model is to be developed in three steps. The first step deals with setting up a finite element model of a repeating unit cell (RUC) of a unidirectional composite material with random fibre distribution. The fibres and the matrix are to be assigned an isotropic elastoplastic material model. Next, the yield surface of the RUC has to be determined through virtual experiments. From the identified yield surface, a phenomenological material model has to be developed. The second step deals with setting up an RUC of a plain weave composite. The tows of the plain weave RUC are to be assigned the developed material model for the unidirectional composite RUC and the matrix an isotropic material model. The yield surface of the plain weave RUC has to be identified as done in the case of the unidirectional composite RUC. Subsequently, a second material model has to be developed to capture the identified yield surface. The final step deals with an extension of the model to finite strain.