Experimental and virtual analysis of draping effect and of their impact on the structural mechanical behaviour of composite components

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The mass of load-carrying structural components can be considerably reduced by using high-performance fibre reinforced plastics. This material class, however, is not yet well-established for safety-relevant medium- and high-volume applications, since the real material behaviour is not sufficiently predictable. One reason is the considerable discrepancy between the real material behaviour, which is significantly influenced by process control, and the idealising assumptions of the available models for structural simulation. Depending on the complexity of the geometry of the component, the fibre architecture is very inhomogeneous and includes varying fibre orientations, varying fibre volume contents and local draping effects like overlaps, gaps and undulations. Only if those draping effects are diagnosed by experiments and are suitably considered in structural simulation, it will be possible to reliably construct complexly shaped composite components.Hence, objectives of the project are the development of methods to precisely detect draping effects in unidirectionally reinforced composites, the formulation of material models to describe the material impact of those draping effects, and the development of a continuous virtual process chain. Using the example of unidirectional non-crimped carbon fibre/epoxy resin composites, the draping effects arising from the preforming process will be specifically considered for construction. Firstly, experimental investigations are conducted to examine how discontinuities develop during draping and how they affect the properties of the composite. Based on that, the impact of those imperfections on the structural mechanical behaviour is investigated and quantified, partly by means of in-situ computer tomography. In order to consider draping effects in the frame of a CAE chain, they need to be detected by draping simulation. Therefore, draping simulations are conducted and experimentally validated using the example of a generic demonstrator component. For structural mechanical analysis of draping effects, simulation models at meso level will be developed and validated to discretely represent the fibre architecture of the non-crimped fabric including all relevant draping effects. Based on both the experimental investigations and the numerical studies at meso level, homogenised material models at macro level will be developed. These macro mechanical models shall describe the deformation and damage behaviour of the inhomogeneous material with sufficient accuracy, including draping effects. The final objective of the project is to properly represent the identified draping effects as well as their structural mechanical impact within a completed CAE chain. Such a continuous process and structural simulation chain promises great advantages for the design of composite components with non-crimp fabrics and, consequently, also an improved exploitation of the lightweight potential of high-performance composite materials.