Scope:

ASTM D7078 produces shear property data for composite materials—material produced from two or more materials with distinct physical and chemical properties. This data is used in research and development, design and analysis, material specification and quality assurances.

Shear properties that can be determined from the V-notched Rail Shear Method include ultimate shear strength, ultimate engineering shear strain, shear chord modulus of elasticity, and shear stress versus engineering shear strain response.

Test Procedure:

Before the test, the composite sample is V-notched. The ends of the V-notched composite sample are clasped between two loading rails. The sample is clasped taut. When the rails start to pull away, the composite sample experiences shear forces through its faces. In V-notched specimens, the shear stress is much more uniformly distributed throughout the sample as compared to specimens without notches. 

Specimen:

V-Notched Rail Shear Method is restricted to following materials: (a) Laminates made from unidirectional fibrous laminae—the fibers are either parallel or perpendicular to the fixture rails, (b) Laminates of symmetric construction, (c) Laminates made up of woven or braided fabric filamentary laminae, (d) Composites reinforced with short fibers that are randomly distributed.

Composite materials used in V-notched testing are essentially laminates. Laminates are materials made from joining several sheets.