Torsion of honeycomb FRP sandwich beams with a sinusoidal core configuration

A combined analytical, numerical and experimental investigation of honeycomb fiber-reinforced polymer (HFRP) sandwich beam samples subjected to torsion loads is conducted. The sandwich panel considered in this study has unique sinusoidal core geometry in the plane extending vertically between face laminates, and it has been used primarily as decking systems in highway bridges. Using a homogenization process and mechanics of materials approach, the equivalent core material properties for the honeycomb core geometry are found, and the material properties of face sheets are obtained by micro/macromechanics. Equivalent material properties of the core and face sheets are then used to evaluate effective torsional stiffness properties of HFRP panels. The torsional analysis includes the evaluation of core equivalent in-plane and out-of plane shear properties and panel apparent torsional stiffness properties. Finite element models using layered shell elements are used to correlate with the analytical and experimental results for HFRP beams samples in torsion. Two types of models are presented in the finite element simulation: an actual geometry model, where the core and face sheet geometry are defined by layer shell elements, and an equivalent plate model, for which the equivalent material properties of the core and face sheets are utilized. In order to verify the accuracy of the analytical and numerical predictions, several honeycomb sandwich beam samples with sinusoidal core waves oriented along the longitudinal or transverse or vertical directions and with different face sheet configurations are experimentally tested in torsion. The present analysis and characterization procedures can be used in design applications and optimization of honeycomb structures, and they can also be employed to verify or refine in-plane and out-of-plane shear equivalent material properties for the present and other honeycomb FRP panels. (C) 2008 Elsevier Ltd. All rights reserved.