A finite element for modeling delaminations in composite beams

Abstract A shear deformable beam finite element with nodes offset to either the top or bottom side has been developed. The delaminated beam is considered as two sublaminates above and below the plane of delamination, and these are modeled by offset beam finite elements. An expression for the J-integral in terms of force and moment resultants in sublaminates connected to the crack tip is derived. From the J-integral two more methods of computing the strain energy release rate have been developed. In the crack tip force method, the strain energy release rate is expressed in terms of forces transmitted by the crack tip rigid element. The second method is similar to the crack closure method used in two-dimensional fracture problems. The effectiveness of the present method is illustrated by analyzing three composite test specimens widely used to measure fracture toughness.