Effect of forced assembly on bearing performance of single-lap, countersunk composite bolted joints – Part Ⅰ: Experimental investigation

This paper presented an experimental study on the effect of forced assembly on bearing performance of single-lap, countersunk composite bolted joints. The forced assembly deformation amounts in bearing tests were chosen according to the acoustic emission (AE) damage detection results of the bending test. 3D digital image correlation (DIC) technology was used to measure out-of-plane deformation and surface strain field. Bearing damage was observed through microscopy after bearing tests. It is found that forced assembly causes pre-tension as well as higher loading eccentricity, thus obviously weakening the effective bearing strength of single-lap, countersunk composite joints. Specimens with forced assembly display S-shape out-of-plane bending under effective tensile loading. The damage degree of the non-countersunk hole is close to that of the countersunk hole, which indicates that forced assembly uniformizes bearing load distribution at countersunk hole while aggravates the non-uniformity of bearing load distribution at the non-countersunk hole.