Improving the Resistance of Lightweight Stone Panels to Fatigue, Fire, and Meteorological Events

Abstract

Lightweight stone panels consist of a thin layer of natural stone bonded to a lightweight yet extremely durable honeycomb core sandwich panel. The sandwich panels comprise aluminum honeycomb cores faced with sheets of either aluminium or fiberglass that have been impregnated with epoxy or phenolic resin. Applying sandwich panels to stone slabs allows for the thickness of the stone to be halved, greatly reducing the material weight and cost. In addition, the increased and stabilized structural performance minimizes the influence of the variability of the stone's mechanical properties on the in situ performance. The advantages of this solution include weight reduction, material and cost savings (including reduced logistics and installation costs), increased mechanical properties, and material reinforcement; the solution is therefore highly valued when an optimal stiffness to weight ratio is required. However, as the difference in the coefficients of thermal expansion between stone veneer and aluminum can have a serious impact on the panel's performance, aluminum skins are not recommended if the application will be subject to temperature variations (e.g., exterior cladding, steam showers). In such cases, fiberglass skins, with a coefficient of thermal expansion closer to stone veneer, are recommended instead. To support the use of lightweight dimension stone panels as the standards for the mechanical properties of exterior cladding products continue to increase, it is necessary to improve the resistance of such lightweight stone panels to fatigue, fire, and meteorological events. This paper details the performance of these materials under severe conditions. In compliance with ASTM D1781, ASTM C393, ASTM C365, special fiberglass and adhesives are being tested to achieve satisfactory results for ASTM E84, ASTM E72, ASTM C297, and ASTM C67 and will support their use in exterior claddings and other applications when the demands of the environment require such performance.