An experimental study of bolt-hole clearance effects in double-lap, multi-bolt composite joints

An experimental study on the effects of variable bolt-hole clearance in double-lap, multi-bolt joints is presented. Joints with different clearances in each hole have been tested and the effects on load distribution, quasi-static strength, fatigue life and failure modes are reported. Strain gauges have been used for measuring load distribution and specialised jigs have been used for positioning the bolts in the holes and drilling the joints. The clearances examined ranged from neat-fit to clearances slightly larger than those allowed in the aircraft industry. Clearance has been found to have major effects on the load distribution; no effect on ultimate quasi-static strength but significant effect on failure initiation load; and quite significant effects on fatigue life.