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) approximate to 7.3) and has stiff facing sheets (ratio of depth d to the thickness (h) of facings approximate to 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 approximate to 15, d/h approximate to 40) is next considered. It indicates that overall bending tends to inhibit delamination growth under quasi-static loading as it tends to keep the delaminated surfaces in contact.