Delamination of Composites and the Scale Effect of Glued Joint Strength

Abstract: The delamination of fibrous composites with a polymeric matrix is the most common type of failure that precedes and accompanies any other type of failure (the rupture of fibers or monolayers, matrix cracking). Therefore, methods for estimating the conditions for occurring delamination remain relevant. Alongside with calculations of stress fields in layered composites and in the zones of glued joints, it is important to estimate the elastic energy required for developing delamination. The elastic energy is accumulated in the bulk of a beam or a plate, whereas it is consumed in proportion to the area of delamination, which causes an inevitable scale effect that consists in decreasing critical stresses while increasing absolute dimensions. This effect can be illustrated by the example of bending and twisting samples made of layered composites, and it should be taken into account when calculating real composite elements based on strength properties determined with the use of small-sized standard samples. © 2023, Pleiades Publishing, Ltd.