Strain energy tensile

Materials Young s Modulus (GPa) Ultimate Tensile Strength (MPa) Critical Stress Intensity Factor K c (MN m- /2) Critical Strain Energy Release Rate, G c (J m-2)... 

Figure 9. Photographs of 0 bare (water-sized) E-glass fiber laminates tested in flexure showing the edge of the specimen. The tensile side fibers failed first, then propagated delaminations along the tensile surface of the specimen. The strain energy is being used to delaminate the specimen.

Cotterell (10) showed that the planes of maximum tensile stress were also principal stress planes and that crack propagation along these planes releases maximum strain energy (t.e., is probabilistically favored). 

A simple explanation for the shape of the fracture envelope starts with the assumption that the tensile curve is linear with modulus E1. The work of fracture or the strain energy per unit volume up to the fracture point is given by... 

The shear component of the applied stress appears to be the major factor in causing yielding. The uniaxial tensile stress in a conventional stress-strain experiment can be resolved into a shear stress and a dilational (negative compressive) stress normal to the parallel sides of test specimens ofthe type shown in Fig. 11-20. Yielding occurs when the shear strain energy reaches a critical value that depends on the material, according to the von Mises yield criterion, which applies fairly well to polymers. 

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