Strength of composite plate with parallel offset misalignment double-bolted joint under bending moment

Design Clinic Research Unit, Department of Aerospace Engineering, Faculty of Engineering, Kasetsart University, 50 Ngam Wong Wan Rd., Ladyaow, Chatuchak, Bangkok, 10900, Thailand

^a Corresponding author: narongkorn.k@ku.th

Abstract

The connection concept of placing only two bolts in offset misalignment against the bending load along the wing span was used for an aerobatic airplane designed in Thailand as a KIT plane to minimize the impact of drilling numerous holes. This concept can deviate the force direction on the holes. The two suitable drilling positions should have the lowest resultant force and highest strength of fiber reinforcement structure. To investigate the strength of the fastener hole when the force deviated from the original orientation, specimens, made from twill weave carbon fiber-epoxy and laid up at ±45-degree orientation, were tested under bearing load according to ASTM D5961 standard. The experimental results revealed that the bearing strength of CFRP material decreases when the force deviation angle increases, so zero-angle deviation of the resultant force on the drilling hole is the most suitable orientation to absorb bolt bearing load. The most suitable pattern of two offset misalignment holes is the greatest horizontal distance at zero vertical distance when it was considered only the effect of the bearing strength and the deviation angle. Moreover, the failure pattern begins to deviate along the fiber orientation when the inclination angle increased.