Interference-Fit Effect on Improving Bearing Strength and Fatigue Life in a Pin-Loaded Woven Carbon Fiber-Reinforced Plastic Laminate

Abstract

This paper presents an experimental investigation on the effect of interference-fit on the bearing strength and fatigue life of pin-loaded plain-woven and cross ply carbon fiber-reinforced plastic laminate (CFRP). Stainless steel pins are installed to five different sized holes on the CFRP specimens to achieve transition-fit and four interference-fits (0.2%, 0.4%, 0.6%, and 1.0%). The quasi-static and fatigue (R = 0.1) properties of the pin-loaded CFRP are then compared to each other. From the experimental results, it is demonstrated that the interference-fit can improve the joint stiffness per unit bearing area, or the joint stiffness, under both the static and dynamic bearing load conditions. The ultimate bearing strength, fatigue life, and joint stiffness of interference-fit samples are higher than those of the transition-fit samples and they are maximized at an interference-fit percentage of 0.4%. Regardless of interference-fit percentage, the fatigue life of a pin-loaded CFRP specimen tends to be proportional to its joint stiffness in the beginning of a fatigue test. During fatigue testing, the joint stiffness of pin-loaded CFRP gradually decreases to the range of 18.8 GPa/mm to 18.6 GPa/mm when bearing failure occurs. The increased joint stiffness by interference-fit delays CFRP hole damage growth by reducing pin displacement under fatigue cycles.