Damage mechanisms in bioinspired helicoidal glass fiber-reinforced epoxy composite laminates for enhanced control of mechanical properties compared to cross-ply laminates

This experimental investigation applies the principles of the single-helicoidal Bouligand structure to design stacking sequences that tailor the mechanical strength properties and failure mechanism of glass fiber-reinforced polymer (GFRP) composite laminates. Four laminate designs with pitch angles of 5°, 8°, 12°, and 15° were fabricated using the vacuum bagging process. All four pitch angles were characterized under flexural loading to identify the optimal flexural pitch angle. Three pitch angles (5°, 8°, and 12°) were compared under low-velocity impact and short beam shear loading. Two pitch angles (5° and 12°) were compared under uniaxial in-plane compression. The performance of these sequences is compared to that of a conventional cross-ply laminate design. The results indicate that the pitch angles significantly affect the strength properties of GFRP laminates. This effect is more pronounced under quasi-static loading compared to low-velocity impact loading. The optimal pitch angle is 12° for flexural and compression loading. It is 8° for short beam shear. It is 5° for low-velocity impact loading. The 5° showed slightly higher impact strength than the cross-ply laminate. The 12° laminate showed compressive strength comparable to the cross-ply laminate. Pitch angle can therefore be used as a design parameter to tailor the mechanical properties of helicoidal GFRP laminates for specific loading requirements.