A Study of Quasi-Static Delamination in Sandwich Structures

Delamination of sandwich columns is studied using a relatively simple cohesive layer model. The model is described in some detail and is incorporated as a user supplied element (UEL) in a finite element package. The model is shown to predict accurately the test results of delamination of a facing sheet of a sandwich member. The accuracy of the model is seen to be superior to a model previously proposed by the authors, which predicts an earlier termination of crack growth. The UEL model is applied to a sandwich column investigated by earlier investigators — a column that is relatively stout (ratio of length (L) to depth (d) ≈ 7.3) and has stiff facing sheets (ratio of depth d to the thickness (h) of facings ≈ 15). The model is able to capture the onset of delamination buckling, sudden delamination growth at nearly constant compression, stable delamination growth and reaching of a limit point of the load carrying capacity. A slender sandwich column with relatively thin facings (L/d ≈ 15, d/h ≈ 40) is next considered. It indicates that overall bending tends to inhibit delamination growth under quasistatic loading as it tends to keep the delaminated surfaces in contact.