Effect of Cyclic Compression Loading On Crushing Response of Polymer Based Composites Sandwich Panels

The objective of work was focused to investigate microstructure of polyurethane foam and cyclic crushing strength of its sandwich structure which made of sisal / coir / bamboo / glass fabrics as reinforcement with polyester resin to form composites skin. The tested sandwich panels were constructed four type of FRP faceplates made of sisal / coir / bamboo / glass fiber reinforcements impregnated in polyester resin in four different material combinations. Each specimen subjected ten cyclic compression loading upto 40% maximum strain. The results indicate that the foams initially harden after the first cycle and then soften in subsequent cyclic loading. The hysteresis loops tend to shrink and approach asymptotically to a steady state before failure both the foam and the skin. The considered damage is in a form of through-width zone of crushed foam core accompanied by a residual crushing in the foam. It is shown that such damage causes a significant reduction of compressive strength. Glass/polyester and bamboo/polyester skin based sandwich structures have superior compressive strength. Coir /polyester based sandwich structure shows next to glass/polyester sandwich structures.