Shear configuration

Initial bondability of anodized surfaces was tested in the lap shear configuration using numerous commercial epoxy adhesives. With one exception, all surfaces proved to be bondable and gave acceptable lap shear values. That exception was an anodized film formed... 

Figure 13.4. Shear configuration for pure E modes (top) and pure B modes (bottom).

One difficulty in making comparisons of joint strengths, using the overlap shear configuration, is that the measured values depend on both the strength and thickness of the adherends. Care should be taken to allow for this, so that differences observed reflect real changes in joint strength and are not merely artifacts of the test method. 

The mechanical properties of adhesive joints are primarily determined by applying an in-plane shear stress to the assemblies. Fig. 23 shows the single lap shear configuration recommended in ASTM D 1002, Federal Specification MMM-A 132 and Federal Test Method Standard No. 175. 

Figure 25 (a) Single lap shear configuration recommended in ASTM D1002 specification, (b) Principle of the die shear tester. 

But what happens to the highly oriented molecules when the shear is removed The randomizing effect of thermal energy tends to return them to their low-shear configurations, giving rise to an elastic retardation. 

Test specimens were prepared by first injection moulding polymer granules into plaques and then machining them into coupons of dimension 90 mm long, 26.5 mm wide and 3.2 mm thick. Natural and CB pigmented coupons were clamped together in a lap-shear configuration and then laser welded. 

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