Biomimetic Composite Structures with Fibre Angle Gradients: Enhancing Energy Absorption via Progressive Failure

As mobility, safety, and sustainability are increasingly important issues today, this work focuses on energy-absorbing structures with fibre-angle gradients along the specimen length. The aim is to create a gradient of material properties in a composite, leading to a significant increase in energy absorption properties due to a more efficient failure. The methodology is based on the biomimetic techno-pull principle, which led to the abstraction of the dactyl club of the Mantis shrimp ( Odontodactylus scyllarus ). The fibre angle gradient was realised with three different single-specimen winding patterns and a honeycomb structure, compared with 87° and 0° single-specimen winding patterns and a 0° honeycomb structure. All specimens were made of regenerated cellulose fibre in an epoxy resin matrix and tested under axial compression at a process speed of 1000 mm min⁻¹. Comparing the two structures, the mass-specific energy absorption for the fibre angle gradient structure is significantly higher at 20.77 ± 2.33 kJ kg⁻¹ than for the 0° fibre angle structure at 4.98 ± 0.99 kJ kg⁻¹, due to progressive failure.