Effects of humidity on shear behavior of bamboo

作     者：Sina Askarinejad Peter Kotowski Faezeh Shalchy Nima Rahbar 

作者机构：Department of Mechanical Engineering Worcester Polytechnic Institute Department of Civil and Environmental Engineering University of Massachusetts Department of Civil and Environmental Engineering Worcester Polytechnic Institute 

出 版 物：《Theoretical & Applied Mechanics Letters》 (力学快报（英文版）)

年 卷 期：2015年第5卷第6期

页      面：236-243页

核心收录：

学科分类：082902[工学-木材科学与技术] 08[工学] 0829[工学-林业工程] 081402[工学-结构工程] 081304[工学-建筑技术科学] 0813[工学-建筑学] 0814[工学-土木工程] 0801[工学-力学（可授工学、理学学位）] 

基　　金：support from the National Science Foundation (NSF) Faculty Early Career Development Program (CAREER) (Grant No. 1261284) 

主　　题：Bamboo Torsion test Humidity Finite element analysis 

摘      要：Bamboo is a naturally occurring biological composite, however its microstructure and hence its properties are very complex compared to the manmade composites. Due to optimization, it can be assumed that the variation in properties along the thickness of the culm be a smooth transition for better bonding strength between layers and to prevent non uniformity in stress concentration. As a consequence, biological structures are complicated and functionally graded. Hence, a realistic model that can capture the mechanical performance of bamboo is valuable in future design of robust multifunctional composites. This paper presents the results of experimental and numerical studies on the torsional （shear） properties of bamboo. The hierarchical and multi-scale structure of bamboo and the distribution of micro-scale fibers are revealed via laser scanning and atomic force microscopy. This information was incorporated into a finite element model to analyze the mechanical behavior of bamboo under torsion and to estimate the shear modulus of bamboo along the fibers. Moreover, the effects of humidity and therefore water content on the mechanical properties of bamboo were evaluated by performing torsion tests on samples maintained in environments with different humidities. Increasing the humidity does not cause a drop in the shear modulus, however, a jump in the shear modulus did occur at around 60% humidity. Results of this study indicate that the highest strength values in samples occurred in environments with humidity levels between 60% and 80% and undergo a significant drop after that. In higher humidities, the samples behave more ductile.