Effect of unequal face thickness on load resistance of sandwich beams

Optimization of sandwich structures for strength to weight under conditions of relatively concentrated loading is surprisingly complex. In the present work, the specific question as to whether improvements in strength to weight of sandwich beams made with fiber composite faces and polymeric foam cores can result from making the loaded face thicker than the unloaded face is addressed. Tests on sandwich beams with foam cores are reported, along with results of analyses using an exact elasticity solution. The results show good agreement between prediction and measurement for the yield loads in the beam specimens. The analysis shows that if a sandwich beam has been optimized for strength to weight with equal face thickness, increasing the ratio of the thickness of the loaded face relative to the unloaded face does not significantly improve the strength. However, for other configurations, e.g. those designed to increase the stiffness of the beam at the expense of the strength, increasing the relative thickness of the loaded face results in significant increases in strength.