Characterisation of textile composites under combined three dimensional load conditions

Abstract

Anisotropic textile composites show nonlinear deformation and complex failure behaviour. In particular three-dimensional reinforced textile composites are characterised by an orthotropic material behaviour. To improve the erformance of Non Crimp Fabrics (NCF) for lightweight structures the material and failure behaviour has to be analysed especially for regions dominated by three-dimensional stress distributions e. g. load introduction areas. Especially for the numerical analyses of thick laminates with significant stresses in thickness direction finite p-Volume-Elements based on hierarchical shape functions are developed and applied to selected structures. With focus on the material behaviour under combined load conditions an experimental procedure was designed. Aiming at the determination of throughthickness material properties a modified Arcan test device was developed that also enables evaluation of strength properties under combined tension and shear loads in material thickness direction of a moderately thick specimen plate. These advantageous small material thickness allows a tufting in thickness direction. By this process a three-dimensional fibre reinforced composite structure is provided that enables higher delamination strength compared to two-dimensional reinforced textile materials. Therefore the modified Arcan test device provides high potential to characterise influences of three-dimensional reinforcements within textile laminates. Furthermore combined test results are derived characterising material behaviour under combined interlaminar-shear and through-thickness tension load conditions. These tests require different specimen geometries for different combined and uncombined load conditions. Preliminary experimental and numerical studies show the optimisation of specimen geometry due to generate well defined stress states for an untufted NCF material. The experimentally determined material parameters serve as basis for a material model to describe the behaviour of three-dimensional reinforced laminates. Numerical simulations of the conducted experiments and structural analyses of a thick double holed plate demonstrate applicability of the material model and its implementation in the developed p-Volume-Element.