Size and aspect ratio are believed to influence the rheology or the flow in the mixture and in turn the mechanical performance of the composites. Fillers and fibres when used in combination are expected to complement each other's performance resulting in better properties for the composite. They also reduce the extent of matrix polymer required in the system. Composites involving fillers and fibres individually and in combination are studied for the level defect population using NDE and the mechanical performance under compression correlated with such an analysis. It was found that inclusion filler-fibre combination besides yielding better physical properties like density also yielded improved mechanical properties like strength and modulus. These properties showed an improvement of about 30-40% as compared to the ones where a single reinforcement either ash or fibre was used. Further, they exhibited uniform distribution of defects whose population was least compared to the situation where only one component (either filler or fibre) as reinforcement was tried.

The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting technique. Presence of gradation is quantified physically by weight method. This paper addresses the effect of weight fraction of fly ash, core to thickness ratio (C/H) and orientation of jute on specific compressive modulus and strength. In each trial five replicates are tested with lower amount of fly ash below the upper skin of sandwich (rubber-up). Results of experimentation are subjected to statistical analysis of variance (ANOVA) to find the influential factor governing the compressive behaviour. Furthermore piece-wise linear gradation is modeled in finite element and strength values are compared with experimental results. Sandwich sample with fly ash content of 40%, C/H of 0.4 and orientations of 30°/60° registered better performance. Specific strength is observed to increase upto 30% filler content followed by stabilization. Finite element results for strength match very well with experimental ones.