The effect of orientations of metal macrofiber reinforcements on mechanical properties of adhesively bonded single lap joints

A method for improving the mechanical behavior of adhesive joints is embedding metal macrofibers to the adhesive layer. The effect of the orientation of metal macrofibers laid across the length and width of the joint (longitudinal and transversal directions) on the strength and elongation at failure of single lap joints (SLJs) was investigated experimentally by testing SLJs reinforced with metal macrofibers laid in different orientations. The experimental results indicated that increasing the number of metal macrofibers in the longitudinal direction improved the shear strength and elongation at failure of SLJs. However, the improvements were found to be dependent on the normalized horizontal distance between the metal macrofibers for which a proper value of 1 was determined. While embedding metal macrofibers in the transversal direction degraded the mechanical properties of SLJs. Finite element analyses were undertaken to investigate the effects of fibers orientation and horizontal distance on the adhesive peel and shear stress distributions. The results revealed that decreasing the horizontal distance between the metal macrofibers laid in the longitudinal direction decreased the adhesive shear stress values indicating improvement of the joint strength, while in SLJs reinforced with metal macrofibers laid in the transversal direction decreasing the fibers distance increased the adhesive peel stress values resulting in joint strength reduction.