Lap joints beveled

Beveled lap joints. These joints are also more efficient than plain lap joints. The beveled edges allow conformance of the adherends during loading, with a resultant reduction of cleavage stress at the ends of the joint. 

Single and joggle lap joints (Figure 7.2) are more likely to cause delamina-tion than scarf or beveled lap joints. Strap joints may be used to support bending loads. ... 

Figure 50 shows the adhesive shear stress distributions for a doublescarf joint and a double butt-strap joint and compares them with ordinary single- and double-lap joints. The double butt-strap joint gives the lowest stress concentration at its middle, but is then identical to the ordinary, parallel double-lap joint at the other end. For this reason, it is suggested that the straps should be bevelled or scarfed so that the stress concentration might approach that of the double-scarf joint. 

It may be useful to the reader to consider as an example the work by Adams et al (1978c) and some of their hitherto unpublished results. They used finite-element methods to examine the stresses in high-performance composites in symmetrical lap joints with parallel, bevelled, scarfed and stepped adherends. The composite adherends were assumed to be linearly elastic type II carbon fibre reinforced epoxy composites with a 60% fibre volume fraction. The mechanical properties of this material are given in Table 3. 

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