Identifying optimal rotating pitch angles in composites with Bouligand structure

Abstract

The Bouligand structure is a typical helicoidal architecture found in various crustaceans in which each layer rotates by a small angle relative to the adjacent one. We present a theoretical analysis to relate the rotation pitch angle to the mechanical performance (interlaminar shear property in this case) of laminas mimicking the Bouligand architecture. For a given laminate, there exists an optimal pitch angle that yields the lowest shear stress. Theoretical models are compared against experimental tests carried out on 32-layer helicoidal carbon fibre laminates with pitch angles of 6°, 9.1°, 12°, 25.7°. The 9.1° is the predicted optimal angle. The results show that this particular architecture with a pitch angle of 9.1° indeed attains the highest load-bearing capability and delays any catastrophic delamination. This provides a fundamental basis to the design of helicoidal structures mimicking the Bouligand architecture.