Fracture mechanics methodologies have been applied in the area of materials selection, The abilities of fracture mechanics to differentiate materials on the basis of their crack growth behavior and to incorporate fracture toughness results into rational schemes for fracture prevention are described. While a single fracture toughness value adequately describes the fracture behavior of linear elastic polymers, it is generally inappropriate for elastic plastic polymers. For these materials, Me entire crack growth resistance curve should be considered.