Fabrication of a bamboo-based glulam based on reconstitution unit innovation: Mechanical property investigation and carbon footprint evaluation

The development of high-quality, large format bamboo structural materials is a hot spot. Here, we fabricated a flattened bamboo board (FB) with a large size, which was further laminated and lengthened to prepare FB-based glulam. Two kinds of FBs were fabricated based on different flattening methods: notched-FB and smooth-FB. Compared with the notched-FBs, the modulus of rupture (MOR) and modulus of elastic (MOE) values of smooth-FBs which were previously softened at 175 degrees C increased by 9.2% and 7.7%, respectively. The FB-based laminated boards whose middle bonding layer is yellow surface to yellow surface show the best mechanical properties among all the three candidates, with dry shear strength, compressive strength parallel to grain, tensile strength parallel to grain, MOR and MOE values of 20.7 MPa, 52.5 MPa, 115.6 MPa, 119.6 MPa and 14.2 GPa, respectively. Finally, two lengthening methods of horizontal and vertical finger connections were introduced to enlarge the size. The results indicate that the FB-based glulam with extension interfaces near to the two terminal points of each laminated boards exhibits better bending resistance with a MOR value as large as 95.9 MPa, being attributed to the corresponding distributed stress and extended the stress transmission distance. The FB-based glulam is proved to be a carbon-neutral product with a carbon footprint value of -1.12 kg CO2/t. This work is the first time to use FBs as reconstituted units for bamboo glulam. We hope to discuss the effects of changes in process parameters and methods at different manufacturing stages on the physical and mechanical properties of the material, thus providing an experimental and theoretical basis for the application of FBs in the field of large-scale bamboo-based structural materials and also broadening the application field of bamboo with high added value.