Double strap lap adhesive joints between metal (AA 6061-T6) and composite (carbon/epoxy) laminates were fabricated and characterized based on strength. Hand layup methods were used to fabricate double strap match lap joints and double strap mismatch lap joints. These joints were compared for their strength under static and fatigue loadings. Fracture toughness (GIIC) was measured experimentally using tensile testing and validated with numerical simulations using the cohesive zone model (CZM) in ABAQUS/Standard. Fatigue life under tension–tension fluctuating sinusoidal loading was determined experimentally. Failure loads for both joints were in close relation, whereas the fatigue life of the double strap mismatch lap joint was longer than that of the double strap match lap joint. A cohesive dominating failure pattern was identified in tensile testing. During fatigue testing, it was observed that inhomogeneity (air bubble) in adhesive plays a negative role while the long time duration between two consecutive cycle spans has a positive effect on the life of joints.

The increasing mortality rate in bike-related road accidents due to head injuries necessitates stronger helmets. This paper presents a cost-effective machine setup to evaluate helmet behavior during impacts. By employing unique methods to measure impact duration and post-impact energy absorption, this project eliminates the need for high-speed cameras. The results indicate that the developed machine enables scenario-based impact tests directly on helmets, providing valuable insights into collision effects. Validation confirms its effectiveness. The low-cost impact testing machine offers a practical solution for studying helmet performance and addressing the rising concerns surrounding bike accidents.