Mechanical properties of cross-laminated bamboo with different structural configurations: Experimental investigation and analytical modeling

Driven by the global demand for green and low-carbon construction materials, Cross-Laminated Bamboo (CLB) has emerged as a viable solution to mitigate the inherent anisotropy of natural bamboo. However, the influence of different cross-sectional configurations on its mechanical properties remains poorly understood. To address this gap, this study investigates two CLB configurations: orthogonal flatwise lay-up and orthogonal flatwise-edgewise lay-up. A comprehensive experimental program was conducted, comprising tension, compression, bending, and shear tests to characterize their performance. The results reveal that the orthogonal layup strategy effectively homogenized material properties, reducing the tensile strength anisotropy ratio from 14.17 in unidirectional flatwise lay-up to 3.62 in orthogonal flatwise lay-up. Regarding structural efficiency, the orthogonal flatwise lay-up exhibited superior stress transfer compared to the orthogonal flatwise-edgewise lay-up, yielding tensile and bending strengths 23.5% and 24.3% higher, respectively. Notably, both configurations demonstrate exceptional bending and shear strengths that significantly surpass those of traditional softwood Cross-Laminated Timber (CLT), positioning CLB as a competitive high-load structural material. Furthermore, DIC observations revealed that flat-pressed cross-laminated bamboo (FCLB) had a broader high-strain distribution and the highest energy absorption, indicating more stable damage evolution during bending. Moreover, the proposed progressive damage mechanics model based on composite laminate theory accurately predicted the behaviors of the engineering bamboo composites, confirming its reliability in describing the effect of laminate architecture on flexural performance. These findings provide essential data and theoretical guidelines for optimizing CLB structural designs.