Comparative assessment of failure in single shear lap joints fabricated using various joining techniques.

• Exploring the novel hybrid joints in natural fiber based composite materials. • Comparing the various mechanical, fusion and hybrid joining techniques in flax/PP composites. • Investigating the influence of number of bolts and bolt diameter on performance of various joints in flax/PP composites. • Investigating of effect of fusion bonding on the crystallinity and thermal decomposition behaviour of flax/PP composites. The current research endeavour reports the performance of single shear lap joints of flax/PP composite laminates. The joints were fabricated using mechanical joining, fusion bonding (ultrasonic and hot plate joining), and hybrid joining techniques (mechanical/ultrasonic joining and mechanical/hot plate joining). In case of the mechanical and hybrid joining, the effect of the bolt size, and number of bolts (single and double) on the tensile failure load was investigated. Pertaining to mechanical joining, the large bolt size and double bolts recorded higher tensile failure load compared to smaller bolt size and single bolt, respectively. Whereas with double bolts, no increase in the tensile failure load was observed for the hybrid joints, due to reduction in bonded area. The hybrid joints (mechanical/ultrasonic) recorded the maximum tensile failure load compared to all other type of joints. The load-extension behaviour and failure of joints was also examined. Expect mechanical joints, all other joints exhibited structural type of failure. In contrast, the mechanical joints resulted in a net-tension failure mode with failure line passing through the hole. However, the thermal decomposition and crystalline behaviour (XRD spectra) of developed joints did not vary significantly. The morphology of failed joints was examined using scanning electron microscope. [ABSTRACT FROM AUTHOR]