Impact of standard and unexpected bolt-hole-washer tolerances on the performance of pinned and torqued joints in CFRP composites

• Published in: Alexandria engineering journal 2023-10, Vol.81, p.290-303
• Main Author: Khashaba, U.A.
• Format: Article
• Language: English
• Subjects: Bolt axial force; Bolt-hole clearance; Bolted joints; Quasi-isotropic carbon fiber composites; Tightening torque; Washer-bolt hole clearance offset arrangements
• ISSN: 1110-0168
• DOI: 10.1016/j.aej.2023.09.037

This study aimed to investigate the impact of some practical assembly errors on the performance of composite joints with M6 bolts in quasi-isotropic CFRP laminates with stacking sequence of [±45/0/90]2S, which are increasingly used in aerospace and automotive industries. The detailed experimental explanations of the behaviors of the bolted joints in CFRP composites with standard and unexpected joining parameters, exhibited a vital impact on the bearing and ultimate joint strength, stiffness, energy absorption, and failure mechanisms. The joining parameters include tightening torque (0-16Nm), bolt-hole clearance (0–240 μm), and washer-to-bolt hole clearance (0–500 μm) with different offset arrangements. The bolt axial force is monitored during the testing of double-lap bolted composite joints. The maximum performance of the bolted joints was observed at tightening torque of 12Nm, bolt-hole clearance up to 60 μm, washer-to-bolt hole neat-fit or with negative clearance arrangement. The first peak, 2 % offset, and ultimate strengths are increased, respectively, by 55.9 %, 56.4 % and 52.4 % compared to those of the pinned joints. The 2 % offset strength and stiffness of bolted joints with negative washer-to-bolt hole clearance arrangements is improved by 26.8 % and 57 % respectively compared to those having positive arrangements. Energy absorption increase almost linearly with bearing load with correlation coefficient of 0.982.