Al/GFRP Interface Strength Under Quasi-Static and Dynamic Loading Conditions

Abstract

AbstractMetal/composite adhesively bonded joints are quite common in aerospace applications since several aircraft components are smaller in size and/or have complex shapes which make it challenging to use riveting, bolting, or welding techniques. Apparently, the interfacial properties in such cases govern the reliability of components. In this investigation, the experiments are conducted to assess the influence of surface roughness and fiber orientation on aluminum/GFRP (glass fiber reinforced polymer) interface strength. Pull test fixtures are designed to conduct the experiments under quasi-static loading condition. To prepare the test samples first the circular surface of Al6063-T6 aluminum alloy cylinders is polished and a surface roughness, ranging from 35 to 175 nm, is developed. The prepared surface is bonded to a 3 mm thick GFRP laminate. Two different sets of laminates, unidirectional (UD) and bidirectional (BD), of the same volume fraction, are considered in the study. The results suggest that the Al/GFRP interface strength increases with decreasing interface roughness. The results also indicate that the bidirectional laminates provide better adhesion when compared to the unidirectional case. The adhesion strength between Al and composite is also measured under ultra-high strain rate loading conditions by employing laser spallation technique. Test samples are prepared by bonding aluminum and GFRP plates of thickness, 1 mm and 0.4 mm, respectively. Failure is instigated at the interface by using high-amplitude short-duration laser-induced stress waves. The failure initiation is identified through optical microscopy. The associated stress wave characteristics, obtained from calibration experiments, are used in computational wave propagation analysis to assess the interface stress. Similar to the quasi-static loading case, the dynamic adhesion strength between aluminum and composite is observed to increase with decreasing interface roughness. The bidirectional laminates again exhibit higher adhesion strength when compared to the unidirectional ones.KeywordsInterface adhesion strengthAluminumGFRPLaser spallation