Modes of failure and microscopic failures of Betong bamboo strips loaded in shear, bending, tension and compression / Shahril Anuar Bahari

Bamboo is an important building material and its potential should be fully utilized. Information on failure properties under load is essential for bamboo to be used as structural materials. In this study, the classification of failure modes, differences of strength properties between failure modes and microscopic failures of Betong bamboo strips were investigated. Specimens were loaded in shear parallel to grain, bending, tension parallel to grain and compression parallel to grain. Specimens were taken from internodes and node parts in bottom, middle and top portions of bamboo culms. From the classification, different failure modes occurred in different portions and parts. In shear, Mode I (Even Splitting) occurred in internodes of all portions and Mode II (Uneven Splitting) in nodes of all portions. In bending, Mode I (Splintering) and Mode II (Simple Tension) occurred in internodes of bottom and middle portions, Mode III (Compression) in internodes of middle and top portions while Mode IV (Brash Tension) and Mode V (Brittle Shear Tension) in nodes of all portions . In tension, Mode I (Splitting) occurred in internodes of all portions, Mode II (Brittle Splintering) in nodes of all portions and Mode III (Grip Splitting) in internodes of top portion. In compression, Mode I (Middle Crushing) occurred in both internodes and nodes of all portions. Strength properties such as Maximum Stress (σml), Stress at Proportional Limit (σpl) and Modulus of Elasticity (E) values between failure modes for all tests were different. Strength properties of failure modes in the same portion and part were not significantly different. Strength properties of failure modes between different portions were significantly different. Similarly, strength properties between failure modes in different parts for all tests were significantly different. From the microscopic observation, the failures occurred in both parenchyma and vascular bundles regions for all classified failure modes from all tests, except for Mode I (Even Splitting) from shear as well as Mode I (radial splitting only) and Mode III (Grip Splitting) from tension test. These modes exhibited failure in parenchyma only, without any failure in vascular bundles regions. Generally, anatomical behaviour had influenced the different modes of failure and microscopic failures of Betong bamboo strips loaded in shear, bending, tension and compression.