||The shear test by DIN EN ISO 14129 or ASTM D 3518 measures characteristic shear values on flat samples with a ±45° fibre orientation. The specimen’s laminate structure is symmetrical and balanced. The testing routine is a static tensile test.
The preface of the norm already quotes limits of this method:
- The method is limited to small deformations only (<5%). Large deformations lead to load shift for horizontal fibre orientation.
- The resulting stress condition in the specimen is multiaxial. The single layer see normal stresses as well as shear stresses. The stresses vertical to fibre orientation additionally cause break between fibre loads which influence the characteristic shear values. Owing to the principle, determining shear strength can’t be done error free.
- The free rims of the specimen cause load shifting effects.
- The load distribution must be assumed to be inhomogenious over the entire specimen width.
On the other hand, the testing routine is impressivly simple. It basically modifies the established tensile test using a smart fibre orientation to create shear stress.