Characterization and modelling of the behaviour of advanced woven composite material

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The current aerospace industry seeks and asks for new innovative materials to be used for primary aircraft components. Because of their structural performance and light weight, composite materials are now increasingly being used in primary aircraft structures. However, conventional laminated composites only have in-plane oriented fibers making them vulnerable to delamination against impact loads. Therefore, interest for using three-dimensional (3-D) woven composites for aircraft applications is rising. Indeed 3-D woven composites offer higher delamination resistance and damage tolerance because of yarns woven in the through-thickness-direction. However, to support their growing use and applications, a better knowledge of their mechanical properties and behaviour until rupture is required. The applicant's research group has recently begun conducting experimental and numerical studies on the mechanical behavior of a 3D interlock woven composite subjected to impact loading. A preliminary model based on a continuum damage mechanics (CDM) approach has been proposed. It uses three damage variables (in the weft, warp and in-plane shear directions) and take into account inelastic strains in the weft and in-plane shear directions. However, the model currently doesn't take into account coupling between the different damage variables and between the inelastic strains. The main objectives of the research proposal are therefore to improve the constitutive laws and develop reliable and robust numerical tools to predict the mechanical behaviour of 3D woven composites. Laboratory experiments will be conducted to determine coupling effects. Improved damage evolution laws will be proposed as well as a new plasticity development law. Additional impact tests will be performed at different energy levels to validate the model. Next, a realistic representative unit cell will be modelled. A progressive damage will be implemented and the finite-element software Abaqus will be used to test virtually the 3D composite and predict its mechanical behaviour. The results of the virtual tests will allow determining theoretically the parameters and variables used in the constitutive equations, plasticity and damage laws of the macroscopic CDM model. Finally, fatigue tests will be conducted to gain a better understanding of fatigue induced damage and failure modes. The developed numerical tools will allow simulating the structure behavior as a function of the 3D-woven architecture used for the composite reinforcement. The simulations will allow to reduce design cycle and minimize the number of components to be tested. The research results will have the potential to lead to numerous applications in the automotive and aeronautical areas.