The Influence of Fastener Clearance Upon the Failure of Compression-Loaded Composite Bolted Joints

摘要

The effects of fastener hole-filling and hole clearance upon the compressive strength of IM6/3501-6 tape composite bolted joints were investigated experimentally and analytically. Tests were conducted using coupon specimens loaded at several bearing-bypass loading ratios, with defined hole clearances spanning the range permitted in Class 1 structural holes (nominal bolt diameter +0.076/-0.000 mm). Bearing-bypass loads were applied using a dual actuator servo-hydraulic load frame augmented with bearing reaction supports. Three primary failure modes (net section compression, offset net section compression, and bearing) were observed. A linear relationship between bearing stress and bypass strain at failure was observed for specimens failing in the offset net section compression mode. Mean joint strengths were found to vary at most 7% due to variances in initial hole clearance. A semi-empirical strength prediction methodology, which uses 2-D finite-element analysis and ply-level quadratic failure theory, was used to interpret test results. Reasonable agreement between experimental data and predicted trends was demonstrated for IM6/3501 -6 tape laminates. Incorporation of bolt elasticity effects and improved failure criteria within the methodology is necessary to improve the accuracy of strength predictions.