Investigation of the Sandwich Plate Twist Test

Analysis and test results for the compliance of the sandwich plate twist test are presented. The analysis utilizes classical laminated plate theory (CLPT) and finite element analysis (FEA). It is shown that CLPT greatly underestimates the plate compliance, except when very stiff cores and compliant face sheets are used, as a result of transverse core shear deformation, not accounted for in this theory. Parametric studies are conducted using FEA to examine the influence of transverse shear moduli of the core and specimen dimensions on the plate compliance. The influences of indentation at load introduction and support locations, and overhang (oversized panel) are also examined. A test fixture is designed where two diagonally opposite corners of the panel are loaded, while the other two corners are supported to provide twisting deformation of the panel. Tests were conducted on square sandwich panels consisting of aluminum face sheets over various PVC foam cores. CLPT was found to greatly underestimate the experimental plate compliance. Finite element predictions of the plate compliance were in much closer agreement with the experimental data.