Study of delamination in composites by using the serial parallel mixing theory and a damage formulation.

X. MARTINEZ; S. OLLER; E. BARBERO

Mechanical Response of Composites.

Springer

Año: 2008; p. 119 - 140

The use of new materials in structural applications implies dealing with new failureprocesses, not existing in traditional materials. One of these is the delaminationphenomenon found in laminated composites. The lost of adherence between thedifferent layers of the composite leads to a reduction of the section strength andstiffness that can finish in a structural failure.The importance of this phenomenon is demonstrated by the amount of authorsthat have developed theories and formulations to deal with it. All authors that havestudied the problem agree that the delamination process is characterized by twomain phenomenons, the crack initiation and its propagation along the composite.Crack initiation can be obtained by comparing the strain?stress state of the material,in the region where delamination takes place, with a critical one [1, 4, 7, 16] or interms of the traction versus relative displacement [2, 3, 13]. And the delaminationpropagation is usually treated opening the mesh to simulate the crack effect where ittakes place. To open the mesh different procedures are proposed. One of them is thevirtual crack closure technique (VCCT) [9], based on the assumption that when acrack is extended, the energy required to open the crack is the same required to closeit. Another procedure, each time more used, is the use of a cohesive zone model[4]. The cohesion elements are placed in the interface of the layers that can sufferdelamination and its propagation is obtained with damage or plastic formulationsapplied to those elements.