Shear loader and performing pure mode II or mixed mode I and mode II shear loading

A shear loader to produce a shear load on a sample, the shear loader comprising:

• a first shearer comprising:
• a first shearing face that provides a shearing plane;
• a first mating face disposed orthogonal to the first shearing face;
• and
• a first knife edge disposed along the shearing plane at an intersection of the first shearing face and the first mating face;
• a second shearer comprising:
• a second shearing face disposed along the shearing plane;
• a second mating face disposed orthogonal to the second shearing face;
• and
• a second knife edge disposed along the shearing plane at an intersection of the second shearing face and the second mating face,
• the first shearer and the second shearer having relative motion in a shear direction that is parallel to the shearing plane to provide the shear load to the sample along the shearing plane;
• a first load cell disposed on the first mating face of the first shearer and comprising a first load face to contact the sample;
• a second load cell disposed on the second mating face of the second shearer and comprising a second load face opposingly disposed to the first load face of the first load cell,
• the first load cell and the second load cell having relative motion in a load direction that is orthogonal to the shearing plane and orthogonal to the shear direction, such that relative motion the first load cell and the second load cell along the load direction subjects the sample to a side load along the load direction;
• and
• a sample region that receives sample and that is bounded by the first mating face, the second mating face, the first load face, and the second load face.