A bioinspired study on the interlaminar shear resistance of helicoidal fiber structures

• Helicoidal fiber structures are created using 3D printed cores and polymers.
• Cutting-and-delaminating fractures exist in reinforced helicoids under shear stresses.
• Modulus ratios and helix reinforcement angles are critical to helicoids.

Helicoidal fibril structures are identified in many natural animals and plants. This research uses an integrated experimental and modeling approach to study the interlaminar shear resistance of bioinspired helicoidal fiber structures. First, helicoidal fiber-reinforced polymeric composites were created using 3D printed fiber cores and polymeric matrices, including plain, ring and helix reinforced helicoidal specimens. Then, monotonic torsional tests were performed to characterize the composite failure under interlaminar shear stresses, and fractographic characterization was conducted to elucidate corresponding fracture mechanisms in each specimen type. Finally, finite element modeling was performed to explore the critical factors on the interlaminar shear resistance of helicoidal fiber structures. The results showed that fiber-matrix modulus ratios and pitch angles of helix reinforcements played important roles on the interlaminar shear resistance of helicoidal fiber structures.