AN ENERGY BASED FRACTURE CRITERION FOR MODE-II CRACK IN FIBER COMPOSITES

The strain energy density factor or S-criterion[1] has been widely used in fracture mechanics and our work confirms that it can be used to explain the cracking behavior of a homogeneous, isotropic solid. However, it was found to be inadequate for some composite materials and a new hypothesis called the Z-criterion, based on the dilatational strain energy density factor and distortional strain energy factor has been proposed by the current authors. Under mode I conditions, the Z-criterion has been found adequately to predict cracking and now this new approach has been applied to an orthotropic material subjected to mode II loading. Under these conditions it is shown that the dilatational component of the strain energy density is insignificant and so a new criterion has been developed. The new criterion show that the distortional strain energy density factor is the dominant factor for mode II crack analysis. © 1990.