Experimental investigation of temperature effects on the tensile behavior of composite-aluminum four-nail bolted joints

The bolted joint is widely used to connect different composite structures in the aerospace field, and the joint is usually the weakest part, and its performance is widely influenced by temperature. This paper aims to investigate the static tensile behavior of the composite-aluminum four-nailed joint structure at different temperatures. Carbon fiber epoxy resin matrix composites with a layup of [(0/45)2s]2 are selected to fabricate specimens, and the test temperatures are room temperature (RT, 25 degrees C), 60 degrees C, 100 degrees C, and 150 degrees C, respectively. The surface strain field and damage evolution inside the specimens are monitored at different stages of the loading process by combining the digital image correlation (DIC) and X-ray computed tomography (CT) techniques. During the loading process at RT, a sudden drop in load occurs after structural yielding, and the following secondary bearing is observed; however, at higher temperatures, the load continuously decreases until final failure after it reaches the peak value. Moreover, the rearrangement of stress distribution around the bolts at higher temperatures relieves the asymmetric secondary bending of the joint. The experimental findings in this study provide valuable guidance for the structural design and safety assessment for composite-aluminum bolted joints at different temperatures.HighlightsThe loading process shows five stages at RT and four stages at higher temperatures.Extrusion damage led by shear cracks appears earlier at higher temperatures.Load on the upper and lower bolts is closer as the temperature increases.Higher temperatures relieve the asymmetric secondary bending of the joint. Damage evolution analysis of composite-Al bolted joints at different temperatures.image