Flexural modeling and failure criteria of thermal modified laminated bamboo beams

Thermal-treated bamboo can effectively prevent insect infestation and mildew, and provide bamboo with superior mechanical properties and richer apparent colors. This study investigated the effects of thermal modification in vacuum at different temperatures and times on the appearance characteristics, flexural properties and microstructure of laminated bamboo, and proposed an equation to predict the flexural strength of thermally modified laminated bamboo based on TTSP. Results showed that the mass loss rate and volume shrinkage of laminated bamboo increased linearly with increasing temperature and time. In the chromatic aberration analysis, higher treatment temperatures caused the color of laminated bamboo to deepen, and the color change is no longer obvious after exceeding 210 degrees C. The color change of the laminated bamboo becomes much less pronounced with increasing temperature and time. The flexural failure morphology of laminated bamboo develops from bending failure to brittle failure with the increase of temperature and time of heat treatment, and its strength shows a trend of first increasing and then decreasing with the increase of temperature. As for flexural strength, thermally modified laminated bamboo showed a maximum improvement of 24.45 %. The overall effect of temperature on the modulus of elasticity is more significant. The maximum increase in elastic modulus is 34.01 % at 230 degrees C. Scanning electron microscopy results show that 170 degrees C is the temperature node at which fiber cell fragmentation occurs in laminated bamboo, and the macroscopic decrease in flexural strength is related to cellulose pyrolysis.