Analysis of force generated in composite egg-box structures during draping as a function of draping angle

To closely investigate the correlation between the structural shape and forces generated along yarns, draping simulation was performed using a non-orthogonal constitutive equation programmed by a VUMAT code and a composite lay-up model considering the draping angle (0 degrees, 15 degrees, 30 degrees, 45 degrees) and the actual thickness of the prepregs. Force generation at seven representative points (RP) along the two major axes (sidewall and saddle) of the unit cell structure was studied during draping. Representative deformations, including wrinkle generation, of the fabric prepregs during draping were correlated to the generated forces. To estimate the onset of wrinkle generation of the draped structure for any draping angle cases, the distortion energy which was calculated using the yarn force and shear angle of a simple square FE model was used. Moreover, draping experiments were conducted to verify the deformation characteristics estimated by finite element analysis.