Collapse behaviour of plastic tubes filled with wood sawdust

The influence of foam-like wood filler on the mode of collapse and energy absorption performance of polyvinylchloride (PVC) tubes has been investigated under quasi-static loading conditions. The mode of collapse of axially crushed PVC tubes has been found to revert from regular three-lobe diamond mode to axisymmetric concertina mode at a certain wood-filling density. The energy absorption capacity of the PVC tubes is enhanced by wood compression as well as by extra stretching in the tube circumference due to shifting from multi-lobe to axisymmetric mode. The collapse of the PVC tubes has been analyzed considering multi-lobe mode, concertina mode and mixed mode. In these models, the interaction of the wood sawdust filler on the final mode of collapse of the PVC tubes has been incorporated. The mean crushing load of the PVC tubes collapsing into the mixed mode is considered as the average mean of that of the concertina mode, the multi-lobe mode and that causing crushing of wood sawdust. Compression tests on wood sawdust were used to extract its mechanical properties and the results have been used in the validation of the analytical model. The analytical results obtained for the mean crushing load agree reasonably well with those from experimental observations.