Preliminary Experiments on the Manufacture of Hollow Core Composite Panels

Abstract

Structural honeycomb panels consist of a lightweight, often paper, honeycomb column core between two thin, stiff face sheets, which results in a very light structure with high strength and stiffness. These panels have long been used in the shipping and aerospace industries and for furniture components in Europe. The wider adoption of honeycomb panels by Canadian furniture manufacturers is hampered by a lack of experience and technical data on their manufacture, properties, and performance. This study attempts to address this missing information with a series of experiments to test the influence of Kraft paper honeycomb type, orientation, cell wall height, and face sheet type on sandwich strength properties (flexural, shear rigidity, and panel deflection). Failure of sandwich panels occurs by buckling of the honeycomb cell walls under the load point; panel load-bearing capacity is significantly improved by the use of stiff face sheets such as plywood. The strongest and stiffest panels are made with small honeycomb cells (16 mm). The extra cost and bulk associated with using paper-laminated pre-expanded honeycomb is not matched by increased bending strength and is therefore unnecessary. Bending strength is significantly enhanced by aligning the honeycomb so that the nodes and ribbon direction are perpendicular to the long axis (loading direction) of the panel due to the ability of the core to flex and conform to the curvature of the face sheets under load. The results from this study offer insights that furniture manufacturers may use to fabricate and potentially improve the properties of honeycomb sandwich panels.