Abstract
The shear buckling strengths of twelve kinds of CFRP laminated square panels clamped on each edge were investigated experimentally and analytically. The experiments were performed by a newly designed test apparatus. Finite element method based on modified HELLINGERREISSNER principle was employed in order to analyse the post-buckling large-deflection behavior. Except unidirectional laminated panels, there is almost satisfactory agreement between the analytical and experimental results for both the buckling load and the post-buckling behavior, and the following properties are disclosed. 1) The buckled shape is three half-wave type and the failure occurs without secondary buckling phenomena. 2) Both buckling load and maximum load vary depending on the stacking sequence of twelve plies of lamination. 3) As for the panels which contain a lot of +45° plies, the effects of material nonlinearity of shear modulus appear before failure. 4) In the case of the present length-thickness ratio which is 200mm/1.4mm, the maximum load is fairly greater than the buckling load, and therefore CFRP panels can be used in the post-buckling state. However, it is noteworthy that the CFRP panel fails almost elastically, different from duralumin plates. 5) From the view point of the maximum load, the FEM analysis yields either [3(0°, 90°)/sym.] or [3(90°, 0°)/sym.] is the optimum lamination, however the experiment yields [2(90°, 0°), -45°, +45°/sym.] is optimum.
