Stacking sequence effect on the fatigue behavior of single lap shear bonded joints

icaf2023 Tracking Number 31

The stacking sequence of composite joints, especially the ply orientation at the substrate/adhesive interface, plays an important role on their fracture behaviour. However, few works are available in this subject, especially under fatigue loading conditions. In this study, the stacking sequence effect on the fracture and fatigue/fracture behaviour of glass-fibre reinforced polymers bonded joints is addressed. Two layups were considered: [0°, 90°, 90°, 0°]s and [0°, 45°, 90°, -45°]2s. Single-lap shear (SLS) specimens bonded with a two-component epoxy-based adhesive system (SikaPower® 1200) were subjected to quasi-static and fatigue testing. Quasi-static tensile tests were executed with the aim of obtaining the load-displacement curves and their respective average fracture ultimate load (Pu). Such tests were conducted at a velocity of 1 mm/min using a Zwick testing machine with a loading cell of 10 kN. Fatigue tests were performed considering a maximum load (Pmax) equal to 40% of Pu. The evolution of the specimens compliance (C=d/P) as a function of the number of cycles (N) was recorded during the SLS fatigue/fracture tests. Every fatigue tests considered a sinusoidal waveform with a load ratio, R of 0.1. Cyclic tests were conducted on a servo-hydraulic Instron machine equipped with a 10 kN load cell at a frequency of 4 Hz (Fig. 1). Fractographic analyses were conducted using a scanning electron microscope (SEM). The failure mechanisms of both stacking sequences were compared and correlated with the fracture strength, compliance and fatigue life results. This paper provides experimental data for composite joints considering different layups and gives important insights on the fracture mechanisms observed under fatigue loading. This information could be used as a guideline in the selection of the best composite joint configuration for high-performance engineering applications