Buckling of composite plates subjected to biaxial loading

Buckling loads and modes of elliptical flat and rectangular stiffened composite plates subjected to biaxial tension-compression loading were analytically predicted using the Ritz method and verified with the experimental studies. The buckling problem of elliptical flat plates was solved using the Ritz method with polynomial displacement functions which included up to 136 terms. The convergence study of both buckling load and mode was also performed to ensure the validity of the solutions. The experimental study was performed on a specially designed testing frame. Shadow moiré technique was used to monitor the buckling mode. Experimental results show an average percentage error of +11.1% in predictions. Overall buckling modes are well predicted.; Buckling behaviors of rectangular stiffened composite panels obtained using the Ritz method without any modifications of plate configurations are presented here for the first time. In the analysis the total potential energy of a stiffened plate is calculated based on assumed displacement fields in form of beam functions. The problem formulation ultimately leads to an eigenvalue problem. The lowest eigenvalue and its corresponding eigenvector are the predicted buckling load and mode, respectively.; Thirty tests were conducted on the rectangular stiffened panels. The measured buckling loads were relatively well predicted. The discrepancy between prediction and measurement in term of percentage error in prediction had an average value of +8.62%. The measured buckling loads increased with an increase in transverse tension, as predicted. The measured buckling modes were also well predicted by the Ritz method, although in some cases the moiré patterns did not perfectly match the predicted buckling mode. The mode number measured in instances of local buckling compared well with predictions. Changes of buckling modes that were predicted due to a change in transverse tension were confirmed experimentally.