Improved hyperelastic model for simulating the forming of biaxial braided fabrics

The complex deformation behavior during preforming of composite reinforcements can be effectively predicted by numerical simulation. Most numerical studies generally concern orthogonally woven fabrics. The present work proposes a hyperelastic constitutive model to characterize the anisotropic mechanical properties of non-orthogonal braided reinforcements to simulate the preforming process. Based on the deformation modes, the strain energy was defined by corresponding specific invariants. The coefficients of the hyperelastic constitutive law were identified in the case of non-orthogonal fabrics thanks to the establishment of an energetic model between the second Kirchhoff stress tensor and the tensile load. The constitutive law and energetic model were then validated by means of comparison with the bias-extension test and hemispherical forming test.