Buckling behavior of composite laminates with multiple delaminations under uniaxial compression

The buckling behaviors of composite laminates with multiple delaminations under uniaxial compression are studied. Different types of multiple delaminations are considered and their effects upon buckling behavior are examined. The nonlinear buckling analysis uses a finite element method, including contact elements to prevent the overlapping situation, to predict the buckling stress and the corresponding buckling mode. The results indicate that as the length of the beneath delaminations is not larger than the length of the near-surface delamination, the beneath delaminations have no significant effects on the buckling stress, such that the buckling behaviors of multiple delaminations are almost the same as those of single delamination. When a short delamination appears above the long delamination, three types of multiple delaminations are investigated. If the length of the short delamination is greater than one critical value, the short delamination above the long delamination will reduce the buckling stress and change the buckling mode. When the short delamination approaches the same length as the long delamination, the buckling stress becomes the Value of the single delamination case. (C) 2001 Elsevier Science Ltd. All rights reserved.