Fracture mechanics using a 3D composite element

The formulation of a 3D composite element and its use in a mixed-mode fract ure mechanics example is presented. This element, like a conventional 3D fi nite element, has three degrees of freedom per node although, like a plate element, the strains are defined in the local directions of the mid-plane s urface. The stress-strain property matrix of this element was modified to d ecouple the stresses in the local mid-plane and the strains normal to this plane thus preventing the element from being too stiff in bending. A main a dvantage of this formulation is the ability to model a laminate with a sing le 3D element. The motivation behind this work was to improve the computati onal efficiency associated with the calculation of strain energy release ra tes in laminated structures. A comparison of mixed-mode results using diffe rent elements of an in-house finite element package are presented. Good agr eement was achieved between the results obtained using the new element and coventional higher-order elements. (C) 1999 Elsevier Science Ltd. All right s reserved.