Prediction of the Crack Kinking in a Sandwich Composite Beam Subjected to Three Point Bending Using the J Integral Concept

Composite materials utilizing the sandwich structure are a basic family of materials and possess a highly increasing use in modern industrial applications. Since the traditional approach to structural design and material selection tends to be replaced by the Fracture mechanics approach, it is worth understanding the way that the Fracture mechanics approach is applied. The traditional approach to structural design takes into account two variables which have to be in contrast: The applied or expected stresses and the Yield or Tensile strength. The Fracture mechanics approach [1,2] involves three important variables rather than two. The additional structural variable is the flaw size, and the Fracture Toughness replaces Yield or Tensile strength. This approach quantifies the critical combination of these three variables. In Fracture Mechanics there are two methods of studying a problem, the Stress Intensity Factors criterion and the Energy criterion. In this study we get involved with the Energy criterion and specifically with the J Contour integral calculation [3-5].