HYPERELASTIC AND HYPOELASTIC MODELS FOR THE MESOSCOPIC ANALYSES OF COMPOSITE REINFORCEMENT DEFORMATION DURING FORMING

摘要

Hyperelastic and hypoelastic constitutive law are proposed to describe the mechanical behaviour of fibre bundles of woven composite reinforcements. The objective of these models is to compute the 3D geometry of the deformed woven unit cell of a composite reinforcement during a forming process. This geometry is important for permeability calculations [1] and for the mechanical behaviour of the composite into service. The finite element models of a woven unit cell can also be used as virtual mechanical tests. The highlight of four deformation modes of the fibre bundle leads to definition of a strain energy potential from four specific invariants used in a hyperelastic approach [2]. The parameters of the hyperelastic constitutive law are identified thanks to uniaxial and equibiaxial tensile tests on the fibre bundle and on the whole reinforcement. This constitutive law is then validated in comparison to biaxial tension and inplane shear tests. On the other hand an hypoelastic model will also be presented to depict the mechanical behaviour of the yarn. It is based on the fibre rotation. The compression responses of several layer stacks with parallel or different orientations will be analysed [3]. The numerical simulations show good agreement when compared to compaction experiments. These mesoscopic simulations can be used as virtual compression tests. In addition they determine the internal geometry of the reinforcement after compaction. There too, this internal geometry is important to compute the permeability of the deformed reinforcement and to calculate the homogenised mechanical properties of the final composite part [4].