Energy-Dependent Impact Behavior of Bio-Inspired Helicoidal Composite Laminates

Fiber-reinforced polymer composites have become the backbone of engineering materials in aerospace, marine, and automotive design because of the reducing weight without sacrificing mechanical integrity, however, impact resistance is still a limitation. For instance, when a structure encounters high-velocity debris or a ballistic strike, damage evolves within microseconds, leaving little room for redistribution of stress. Traditional cross-ply and quasi-isotropic laminates, though optimized for stiffness and fatigue strength, still tend to fail by delamination or catastrophic cracking that slices through the laminate thickness. It is this inherent weakness that has turned researchers’ attention toward nature’s own defensive architectures. One particularly intriguing concept is the helicoidal, or Bouligand, structure found in crustacean exoskeletons such as the mantis shrimp’s dactyl club. In these biological composites, each fibrous layer is rotated slightly relative to the next, forcing cracks to follow tortuous spiral paths and dissipate energy gradually. Translating this geometry into synthetic composites has yielded impressive toughness gains in low-velocity impact tests, especially when the inter-ply angle is small enough to maintain interlayer continuity. What remains less clear is how such helicoidal designs behave when the loading rate increases dramatically. At extreme velocities, strain-rate effects, stress-wave reflections, and fiber–matrix debonding interact in unpredictable ways. The same twisting arrangement that aids energy absorption under moderate impact may disrupt stress transfer when the event becomes violent. Understanding whether these bio-inspired structures can endure that transition remains a central challenge for composite mechanics today.

To this account, new research paper published in Polymer Composites and conducted by Prof. Wei Chen, Mr. Haoming Lin, Dr. Mengzhen Li, Dr. Yiheng Zhang, Mr. Hai Huang, Mr. Xingxing Wu, and Prof. Xiaobin Li from the School of Naval Architecture, Ocean and Energy Power Engineering at Wuhan University of Technology, the researchers developed two complementary models: an experimental ballistic impact framework using dual light-gas guns and a finite element simulation model incorporating the Hashin failure criterion and dynamic increase factors. The research team fabricated carbon–epoxy helicoidal laminates with varying helix angles while keeping the fiber volume fraction and matrix type constant. Two different light-gas gun setups were used to generate both low- and high-velocity impacts, and a laser velocimeter measured projectile velocities before and after impact. The laminates were clamped rigidly to prevent boundary deformation, ensuring that observed failures reflected true penetration and delamination behavior. Damage features were analyzed using scanning electron microscopy and ultrasonic C-scan imaging to map delamination areas and fracture morphology.

The authors found at lower impact energies, helicoidal laminates exhibited a pronounced capacity to absorb energy through controlled delamination. The laminate with a 15-degree helix angle displayed the largest delamination area and the lowest residual projectile velocity, indicating the highest energy absorption efficiency. The gradual fiber rotation between adjacent layers created multiple shear planes, distributing impact energy along tortuous paths and reducing localized stress concentration. These mechanisms helped to slow crack propagation and prevent abrupt perforation, which validated the energy-dissipative nature of helicoidal structures under mild impact conditions. However, as the impact velocity increased, the same architectural feature became less advantageous. At high energy, the 15-degree laminates exhibited excessive interfacial shear and matrix fragmentation, leading to earlier onset of fiber breakage. In contrast, laminates with a 45-degree helix angle showed significantly lower delamination—about 35% less than their low-angle counterparts—and maintained better structural coherence. The higher-angle configuration restricted interlayer sliding, allowing the laminate to resist further damage propagation during severe impact. Afterward, the authors performed finite element simulations implemented in ABAQUS, using the Hashin failure criterion and revised dynamic increase factors, aligned closely with the experimental findings. The models showed that stress waves in low-angle laminates decay more quickly but cause concentrated interfacial stress, while in high-angle designs, wave energy spreads more laterally, reducing penetration likelihood. These complementary findings demonstrate that helicoidal performance is not fixed but strongly dependent on impact energy. The structure that maximizes energy absorption under gentle conditions may underperform under extreme loads, where delamination control and stiffness become more critical. Consequently, an optimal helix angle must be chosen according to the operational impact regime, balancing toughness and integrity for different applications.

In conclusion, the study led by Professor Xiaobin Li and colleagues advance our understanding of how bio-inspired helicoidal laminates behave under different impact energies, and clarify the critical transition between low-velocity and high-velocity responses. Their work demonstrates that impact performance is strongly energy-dependent and revealed that laminates with smaller inter-ply angles absorb and dissipate kinetic energy efficiently during mild impacts, while those with larger helix angles preserve structural integrity when subjected to extreme loads. This duality defines a clear design principle—impact energy should dictate the optimal fiber rotation rather than relying on a single “best” configuration.
From a practical standpoint, these findings transforms how engineers might design lightweight protective systems in aerospace and marine applications. Structures likely to experience moderate impacts can benefit from low-angle helicoidal layouts, which enhance energy dissipation through controlled delamination. Conversely, high-angle configurations are more appropriate in ballistic or high-speed environments, where maintaining laminate coherence outweighs the benefits of additional delamination. The study therefore replaces a generalized biomimetic approach with a calibrated, condition-specific framework that balances energy absorption and damage restraint. We believe the novel methodology is also important because the integration of light-gas gun experiments, laser velocimetry, and scanning electron microscopy with finite-element modeling provides a reproducible route for linking microscale failure features to macroscale response. It allows accurate prediction of damage evolution before large-scale fabrication, a capability essential for next-generation composites. By recognizing strain-rate sensitivity as an intrinsic design parameter, this study encourages a more adaptive vision of biomimetic engineering—one that couples natural design logic with modern analytical precision to create composites that respond intelligently to their energy environment.