Analysis of multi-bolt joints

To measure load distribution, standard aerospace bolts were fitted with strain gauges. Both shear and axial load could be measured. A three-dimensional finite element model with linear elastic material properties was developed for calculation of load distribution prior to initiation of material failure and comparison with instm-mented bolt results. Model details are similar to those of the single-bolt model above, with a full contact analysis being performed for all bolts, washers and holes. 

2 Failure prediction using bearing-bypass diagrams 

For this study, two different joint configurations were considered. The first was a C1 C1 C1 joint with neat-fit clearances at each bolt-hole, and the other (C4 C1 C1) had a 240 pm clearance at bolt-hole No. 1, as shown in Table 11.4. 

Three tests to failure on the C1 C1 C1 joint configuration were carried out in [41]. The study found that one joint failed in net-tension at hole 1 in the lower laminate at a joint load of 80 kN, while another failed by net-tension at hole 3 in the top laminate at 84 kN. The third joint tested failed by bolt failure at 76 kN. It should be noted that bearing damage was evident at holes where bolt failure occurred. However, as this damage mode is non-catastrophic, high loads are transferred through the bolt until 

4 Load distribution in iarge Joint assemblies and effects of missing fasteners 

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