Flexural, compressive, and low‐velocity impact behavior of bioinspired helicoidal glass fiber/epoxy composites under different loading rates

Abstract This paper investigates the mechanical properties of bioinspired single helicoidal (SH) and double helicoidal (DH) glass fiber‐reinforced polymer (GFRP) composites at varying loading rates. Twenty‐layered GFRPs (0°//0° midplane and a 10° pitch angle variation) for both SH and DH were fabricated using a hand lay‐up followed by vacuum bagging method. The samples were tested in flexural and compressive loadings at strain rates of 1 and 10 mm/min, and low‐velocity impact (LVI) tests at 2 and 4 m/s. The SH laminates exhibited higher flexural load capacity (122%), strength (96%), and modulus (122%) than DH laminates at a 10 mm/min rate; nevertheless, DH laminates had higher displacement at peak load (78%) and energy absorption (19%). In compression loading, SH laminates showed reduced load capacity and strength as loading rates increased, while in DH laminates, it improved. During LVI, SH laminates had the highest load capacity (4950 N) and displacement (6.25 mm) at 4 m/s; however, DH laminates had 133% less visible damage area. The result highlights that SH and DH designs exhibit distinct features and failure mechanisms due to unique structures, allowing better control in tailoring the mechanical properties of FRP composites based on specific application requirements. The findings aim to advance the properties of GFRP using a biomimicry approach for high‐performance structural applications in automobiles, aerospace, and related engineering fields. Highlights SH laminate show higher flexural modulus. SH had higher compressive strength at 1 mm/min, while DH had it at 10 mm/min. In LVI, DH and SH bear 15% and 20% more load at 2 and 4 m/s, respectively. SH laminates fail with twisted cracks, while DH laminates fail via delamination. DH laminates have smaller damaged areas, enhancing impact resistance.