Experimental study on the deformation and failure mechanism of parallel bamboo Strand Lumber under drop-weight penetration impact

This paper reports an experimental investigation on impact response of Parallel Bamboo Strand Lumber (PBSL) samples when subjected to drop-weight penetration on partial cross-section. A total of 42 samples with 40 mm square cross-sections were tested with 20 mm hemispherical impactor to simulate partial impact resistance with special emphasis on height of specimens and the corresponding fibre orientations. Two typical material responses were observed i.e. penetration-rebound under low impact level (25.4 J) and penetration-failure under high impact level (76.3 J). Since there is currently no standard available for testing of PBSL under impact loading, effect of specimen height was investigated in regards to the ultimate load carrying capacity, deformation capacity and energy absorption ability in both response modes. In addition, penetration-critical failure modes were investigated using electron microscopes. Obtained results indicated that the ultimate load carrying capacity of PBSL was limited by their critical failure energy; however, their deformability and energy absorption capacity increased with increasing impact levels. Failure mechanism of PBSL relies strongly on the fibre orientation i.e. bulking failure with column-like separations was observed when impact load was applied parallel to the fibres, whilst tearing failure with inverted triangular separations was observed in specimens that were tested perpendicular to the fibres. Microscopic images were taken to conduct an in-depth analysis of the observed differences between failure patterns. Specimens with grains perpendicular to the impact load were observed to be more brittle and sensitive to impact load.