Fabrication of crack-free flattened bamboo and its macro-/micro-morphological and mechanical properties

Abstract

This work aimed to help the bamboo industry develop methodology for producing imperfection-free bamboo boards that can serve either decorative or structural benefit to consumers seeking to engage with the bioeconomy. Specifically, softened and slotted bamboo tubes were handled by a roller device with nails to render crack-free flattened bamboo board. Softening temperature and time were optimized herein according to findings regarding chemical composition and board mechanical properties. The optimal softening parameters for saturated steam heat treatment is proved to be 160°C for 8 min. The flattened bamboo board possesses an increased bending strength of 101.5 MPa and a decreased bending modulus of 7.7 GPa, being compared with only-softened bamboo. The corresponding changing mechanism is determined in-depth by the micro-morphological and mechanical results based on in-situ SEM and AFM technologies. Under the action of nails and rolling processes, the bamboo texture becomes compact with crushed and fragmented conduit walls. The resulting cell cavity then becomes stretched and compressed, taking on a morphology which allows for the mechanical penalties associated with flattening to be avoided. According to the micro-mechanical results obtained by AFM, compared with unflatten bam-boo, the Young’s modulus of the cell membrane in transverse direction (YT) decreases to 1.00 GPa while the corresponding Young’s modulus in radial direction (YR) increases to 7.29 GPa.