Failure analysis of joints

Using the unidirectional stiffness properties of the composite material (HTA/6376) in Table 11.1, the laminates were modelled with one orthotropic solid element per ply in the thickness direction, leading to 16 elements through-thickness for both the splice plate and skin plate. As before, the titanium bolts were modelled with isotropic material properties, with material constants Eb = 110 GPa, Vb = 0.29. Linear 8-node hexa-hedral brick elements with a reduced integration scheme were used for the laminates and bolts. This element formulation was used to reduce the cost of the analysis and size of the output files, which were very large. 

3 Load-redistribution after bearing faiiure in multi-bolt joints 

Results from two joints with different clearance configurations are presented here. The first joint, designated C 1 C C 1, represented the control case having a neat-fit at each hole. The second joint, designated C3 C3 C 1 (see Table 11.4 for the clearance codes), had a 160 pm clearance at holes 1 and 2 and a neat-fit at hole 3. 

Joint Code Load at first significant failure (kN) Percentage difference from Joint A Load at first significant failure (kN) Percentage difference from Joint A 

In this section, the effects of clearance on the damage response of the C1 C1 C1 double-lap joint (i.e. a control case) and the C3 C3 C1 double-lap joint (i.e. a worst case scenario in the sense that all the load is initially carried by one bolt) are investigated. The progression of damage in the joints is shown at applied load levels of 10,30 and 50 kN for the four different failure modes considered, i.e. tensile matrix failure compressive matrix failure tensile fibre failure and compressive fibre failure. These load levels were chosen so that the damage could be tracked fiom initiafion up to the point of extensive damage. 

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