ASTM D7078 / D7078M – 12 : Standard Test Method for Shear Properties of Composite Materials by V-Notched Rail Shear Method
This test method covers the determination of the shear properties of high-modulus fiber-reinforced composite materials by clamping the ends of a V-notched specimen between two pairs of loading rails.
When loaded in tension, the rails introduce shear forces into the specimen through the specimen faces. In comparison, the specimen of Test Method D5379/D5379M is loaded through its top and bottom edges. Face loading allows higher shear forces to be applied to the specimen, if required.
Additionally, the present test method utilizes a specimen with a larger gage section than the V-notched specimen of Test Method D5379/D5379M.
In both test methods, the use of a V-notched specimen increases the gage section shear stresses in relation to the shear stresses in the vicinity of the grips, thus localizing the failure within the gage section while causing the shear stress distribution to be more uniform than in a specimen without notches.
In comparison, Test Method D4255/D4255M utilizes an unnotched specimen clamped between two pairs of loading rails that are loaded in tension. Also in contrast to Test Method D4255/D4255M, the present test method provides specimen gripping without the need for holes in the specimen.