Author: Cheng Wang

Publisher:

Published: 1986

Total Pages: 530

ISBN-13:

The buckling and postbuckling behavior of laminated non-coplanar thin-walled structures have been investigated in the present study. A 32 degree-of-freedom assumed stress hybrid semiLoof finite element has been developed and utilized as the analytical tool. Based on the new balanced stress and displacement fields technique, an optimal stress pattern for the element model has been obtained. The programs for the buckling and postbuckling analysis have been separately made by using the new element model. For some standard problems and for the prediction of the buckling and postbuckling behavior of channels and square tubes, the analysis gives good results. The experimental program consisted of the testing of four kinds of specimens: channels, tubes, stiffened plates and stiffened sections. The results show that the postbuckling behavior of those specimens is not sensitive to slight initial imperfections but the prebuckling region is greatly affected. The square tubes with unsymmetric layups showed no initial deflection before the buckling load, which indicated that the square tube arrangement overcomes the unsymmetric elastic coupling effects in each individual side, i.e., the B matrix effects can be neglected effectively for the square tube arrangement. From the results of tube specimens it has been identified that the ratio of D11 /D22 plays a significant role in the determination of the deflection mode shapes, while the value of the buckling load is dominated by the parameters D22 and D66. The channels and square tubes failed by pii delamination at the corners due to stress concentrations and large out-of-plane deflection, while the failure of the stiffened plates and the stiffened sections were first caused by delamination of the base-plate from the square tube core of the stiffeners and covering face-sheet, and finally completed by ply delamination at the stiffener corners.