On the equivalent flexural rigidity of sandwich composite panels

The very graphic name of ‘sandwich composites’ adequately describes them as structures with a relatively thick core made of lightweight or low density material separating two thin stiff and strong skins. Such choice of geometry and combination of materials yields a product with reasonable strength and bending stiffness in combination with lightness. This paper presents work in predicting the bending stiffness of a sandwich composite through its equivalent flexural rigidity by modelling the material in the geometry of a cantilever beam. The results are verified experimentally by obtaining, through the laser based optical NDE technique known as Electronic Speckle Pattern Interferometry (ESPI), the displacement curve of the cantilever beam subjected to a point load at its free end. A second experimental technique carried out involved monitoring the dynamic response of a cantilever beam in its first mode of natural vibration. The beam equipped with polyvinyldiene fluoride (PVDF) sensors yielded results which are compared to the values for the flexural stiffness obtained by the prediction and the experimental setup using ESPI.