Local buckling analysis of composite laminate with large delaminations induced by low velocity impact

Abstract Large delaminations can be induced by a low velocity impact on a laminated composite. The local buckling behavior of a laminated composite containing large delaminations is not as well understood as that with small delaminations. This paper presents analytical modeling of the local buckling behavior of a laminated composite containing a large elliptic delamination embedded near the surface and rested partially on a Winkler foundation. A formula for estimating the elastic modulus of the Winkler foundation is also proposed based on an elastic model. It is shown that the buckled shape predicted by the proposed model is similar to the experimentally observed shape. A small portion of the delaminated sub‐laminate between the delamination tip and the inward portion is found to show slight deflections outward. The first buckling mode takes place at higher mode shapes with a more flexible sub‐laminate, larger delamination, and a stiffer Winkler foundation. Increasing the transverse elastic modulus of the laminate within a certain extent, decreasing the size of the delamination, and enhancing the stiffness of the delaminated sub‐laminate are effective in increasing the local buckling resistance.