Optimal interply angle of bio-inspired composite curved panels with helicoidal fiber architecture

Abstract

The exoskeleton structure of mantis shrimp’s dactyl clubs presents an extraordinary helicoidal reinforcement pattern, holding immense potential for revolutionizing fiber-reinforced composite materials. While extensive investigations have shed light on its unique advantages, the inherent nature of curved Bouligand structures remains incompletely comprehended. To elucidate these unexplored characteristics, the present study introduces a novel analytical model to efficiently calculate the interlaminar shear and normal stresses in helicoidal laminated curved beams under transverse loading. The analytical model systematically determines the optimal uniform fiber interply (pitch) angle for these bio-inspired structures with an arbitrary number of layers. The computational analysis revealed that achieving minimum interlaminar stresses always requires the precise orientation of π or 2π helicoids along the laminate thickness when the number of layers exceeds two. This theoretical discovery is remarkably identical to the study of stacked chitin fibrils in arthropod clubs reported in the literature. For a 37-ply composite, the flat and shallow-curved beam configurations primarily resulted in a 5° optimal pitch angle, while the deep-curved configuration yielded a 10° optimal angle. To validate the model, three-point bending testing were performed. Four fiber pitch angles were thoroughly examined, including the optimal and quad angles. The digital image correlation (DIC) technique was employed to analyze the structural responses and detect the onset of delamination. The numerical and experimental results demonstrated good consistency, exhibiting significant enhancement in the delamination resistance of up to 30 percent with the optimal angle.