Lap joints double

Several authors [4,6,8,55,56,63-65,83] have considered the effect of adhesive plasticity and have shown that, as for the single lap joint, such behaviour reduces the calculated stress concentrations. Hart-Smith has conducted an extensive examination of this effect and Fig. 6.22a illustrates some typical results. As for the single lap joint, the load the joint can withstand increases as the overlap length, /a, increases for short overlaps but no further strength is to be gained beyond a certain point. It will be recalled that the reason behind this observation lies with the stress distribution in the joint, i.e. the maximum stress and strain concentrations are located at or near the ends of the overlap, and 

Hart-Smith has also [4,66,83] considered the out-of-plane transverse tensile stresses, crn, which are developed across the adhesive layer and which are at a maximum at the ends of the overlap of the outer substrates. The maximum value of these stresses, o-ii(max), is given in Fig. 6.23 and the ratio crn(max)/ ri2(max) is given by  

Constant length of plastic deformation as overlap length is now further increased 

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BOND PARAMETERS AFFECTING FAILURE OF CO-CURED SINGLE AND DOUBLE LAP JOINTS SUBJECTED TO STATIC AND DYNAMIC TENSILE LOADS... 

Fig. 2. Photograph of the co-cured lap joint specimens, (a) Co-cured single lap joint (b) co-cured double lap joint.

Figure 4 shows typical failure surfaces obtained from tensile tests of the co-cured single and double lap Joint specimens. In the case of the co-cured single lap Joint, as the surface preparation on the steel adherend is better, a greater amount of carbon fibers and epoxy resin is attached to the steel adherend. Failure mechanism is a partial cohesive failure mode at the C ply of the composite adherend. In contrast with the co-cured single lap joint, failure mechanism of the co-cured double lap joint is the partial cohesive failure or interlaminar delamination failure at the 1 ply of the composite adherend because interfocial out-of-plane peel stress... 

Bond Parameters Affecting Failure of Co-Cured Single and Double lap Joints... 

In this study, residual thermal stresses were also eonsidered because co-cured lap joints generally undergo temperature drop (from 120D to 20D) during the curing process. The stress distributions in the co-cured single and double lap joints were analyzed using ABAQUS i.8 to be commercial finite element analysis software [21],... 

Fig. 8. Coordinate system of the co-cured single and double lap joints for calculating stress distributions in the ply-axis.

The co-cured single and double lap joints were modeled as a three-dimensional solid structure. The resin layer was ignored in this analysis because the average thickness of the resin layer... 

Fig. 12. Interfacial out-of-plane transverse stress distribution, a , of the co-cured double lap joint along the interface between steel and composite adherends. (a) [0]i6t stacking sequence and (b) [+45]4S stacking sequence.

Figures 12 and 13 show interfacial out-of-plane transverse and shear stress distributions of the co-cured double lap joints with [0]i6t and [ 45]4s stacking sequences along the interfaces between steel and composite adherends, respectively. It is important to consider interfacial out-of-plane shear stress rather than interfacial out-of-plane transverse stress because of the compressive stress distribution due to the symmetric configuration of the co-cured double lap...

Based on the failure mechanisms and stress distributions at the interface between steel and composite adherends of the co-cured single and double lap joints, tensile load bearing capacities of the two joints were evaluated. Since failure started at the edge of the interface between steel and composite adherends, it is important to consider the failure criterion using interfacial out-of-plane stress distributions at the interface. Three-dimensional Tsai-Wu and Ye-delamination failure criteria were used to predict partial cohesive failure or interlaminar delamination failure in the co-cured single and double lap joints. 

Equation (1) must be less than 1 failure is predicted when F/ is > 1. Based on the three-dimensional Tsai-Wu failure criterion, tensile load bearing capacities of the co-cured single and double lap joints were calculated. 

Fig. 15. Comparison of tensile load bearing capacities of the co-cured double lap joint (fabricated under 0.7 MPa manufacturing pressure) calculated from the two failure criteria with experimental results.

Failure mechanism of the co-cured double lap joint imder cyclic tensile loads was a j artial cohesive failure in the thin adhesive layer. Figure 17 shows the relationship between the... 

Manufacturing pressure in the autoclave during curing process affect a little tensile load bearing capacities of co-cured single and double lap joints. 

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