1. Rail Shear Test:

This is a very popular method used to measure in-plane shear properties. This method is extensively used in aerospace industry. The shear loads are imposed on the edges of the laminate using specialized fixtures. There are two types of such fixtures: Two rail and three rail fixture.
The ASTM D4255 standard covers the specification for two and three rail specimens for both continuous and discontinuous (  and  fibre alignment), symmetric laminates and randomly oriented fibrous laminates.

a. Two Rail Shear Test
:

The two rail shear test fixture along with a laminate to be tested is shown in Figure 8.12. The Figure 8.13 shows the specimen geometry according to ASTM D4255 standard. The two rail shear test fixture has two rigid parallel steel rails for loading purpose. The rails are aligned to the loading direction as shown in Figure 8.12. Thus, it induces the shear load in the specimen which is bolted to these rails. A strain gage is bonded at  to the longitudinal axis of the specimen.

The Shear strength is obtained as

(8.28)

where,  is ultimate failure load,  is the specimen length along the rails and   is the specimen thickness.