Cohesive elements in finite element analysis allow you to model the progressive delamination (disbonding in broader terms) between the substrates, which for example are the individual plies in a composite laminate. Cohesive elements obey the so-called traction-separation law which relates the "cohesive traction" to the "relative separation". Prior to "damage", the cohesive elements bind the two surfaces of adjacent substrates ("plies") and allow them to deform together as there is no "crack" between them. Once the damage initiation criterion is met (i.e. the combination of stress levels and strength values), the cohesive element start "degrading", i.e. the amount of stress/traction they transmit between the adjacent substrates is reduced. This is achieved by gradual decrease of the cohesive element stiffness based on a certain chosen energy dissipation law. Once all the stiffness is lost, i.e. the cohesive element can support no stress, this implies that you have created a "traction free surface" between the substrates, i.e. there is a disbond between the substrates.

Cohesive elements are available via the standard libraries of all major commercially available finite element software (such as ABAQUS and ANSYS).