Effect of imbalanced interface pre-tightening force on the bearing behavior of carbon fiber reinforced polymer interference-fit lap joint

Abstract

Interference-fit is attracting increasing attention in the aerospace field because of its excellent enhancement of the sealing and fatigue life of carbon fiber reinforced plastic (CFRP). However, it also induces imbalanced pre-tightening forces on the interface, and affects its mechanical behavior. A series of experiments were conducted to assess the imbalanced pre-tightening force of CFRP interference bolted joints and its effects. High-precision washer force sensors were used to measure the pre-tightening force between upper and lower surfaces at various interference-fit and torque. Strain gauges were used to estimate the varying effect on the imbalanced pre-tightening force during tensile tests. The effects of varying interference-fit and torque on pre-loaded transfer, surface strain distribution, tensile strength, and damage mode were identified. The results show that the synergy of interference-fit and torque induces an imbalanced pre-tightening force, which, in turn, changes the stress-strain evolution of the surface, and a special “transition regime” was identified in the evolution curves. Compared with clearance-fit, the ultimate strength and optimal torque of interference-fit joints could be significantly enhanced. In addition, the damage originates from fiber/matrix slipping to the upper surface with a low pre-tightening force and the formation of stack buckling, which then causes delamination fracture.

Joining processes of CFRP‐Al sheets in automobile lightweighting technologies: A review

“…The principal factors affecting the bolt joining strength of carbon fiber laminates are preload, interference amount, nail head form and so on. Li et al [23] F I G U R E 2 Schematic diagram of FJF bonding joint structure [12] F I G U R E 3 Structure diagram of T type bonding joint (A) π type bonding joint (B) [14] F I G U R E 4 Schematic diagram of bolted joining structure [22] studied the influence of the imbalanced pre-tightening force of CFRP interference bolted joints. The results show that interference fit and tightening torque can affect the stress-strain evolution of upper and lower surfaces, and the ultimate strength and optimal torque of interferencefit joints could be significantly improved compared with that of clearance-fit.…”

Study on Effects of Geometric Parameters on Tensile Strength of Hybrid Bonded-Rived Joint of Fiber Reinforced Polymer Plates

“…It was found that the damage to the joint was dominated by laminate damage, which occurred mainly at the entrance and exit of the hole and was strongly influenced by the size of the interference. Li et al [9] investigated the combined impact of fit and preload torque on joints and showed that. The joint has better mechanical properties with both interference fit and preload torque.…”