Polymeric foams and sandwich composites: Material properties, environmental effects, and shear-lag modeling

Marine composite sandwich structural materials, comprising of low density PVC foam core and carbon fiber reinforced vinyl ester based resin composite facings, are studied for associated degradation in mechanical behavior caused by sea water. This paper presents experimental and analytical results concerning the properties and response of closed cell polymeric foams (PVC H100) and their sandwich composites. Data regarding the elastic properties of foam (shear and Young’s modulus) are collected by means of novel custom made devices and interpreted by means of displacement based analytical models. Emphasis is placed on environmental effects and a novel approach of using expansional strain analogy to study the effects of both sea water and temperature are proposed.It is shown that the custom made shear testing apparatus employed herein offers a significant improvement over the device recommended by ASTM. Using torsional testing, the value of shear modulus in the water-saturated outer shell of soaked foam samples are obtained and show a degradation of 72% with long-term exposure to sea water.