When comparing the flexural strengt

When comparing the flexural strength of different parts of bamboo samples, the densified outer bamboo exhibited a higher flexural strength of 404 MPa and a modulus of 46.5 GPa, as the percentage of the fibers is higher in the outer part of bamboo (Figure 4E,F). This mechanical characterization demonstrated that the outer part of the bamboo with a high fiber volume fraction exhibited higher flexural strength and modulus com- pared to the inner part (Figure S17, Supporting Information). For the same cross-sectional size, we observed different failure modes for the natural and densified bamboo samples after flex- ural behavior test failed (Figure 4G). There is obvious fracture at the bottom surface of the natural bamboo sample, whereas no crack was seen in the densified bamboo. Scalable produc- tion of structural materials with excellent mechanical proper- ties is highly desirable in the construction and transportation fields. The large piece of bamboo-based structural material was prepared by a three-step approach, involving slotting, sof- tening, and flattening treatment. Figure 4H demonstrates a longitudinally cut bamboo stem with two nodes (left) and after flattening (right) bulk bamboo in the size of 82 cm by 22 cm by 0.9 cm. This large natural flattened bamboo as well as the small bamboo chip could keep the block-shaped structures after the delignification treatment (Figure S18, Supporting Informa- tion). The resulting flattened bamboo board can then be used in preparing the densified bulk bamboo with light weight and high mechanical performance. One of the potential concerns for use of bamboo for structural material is the periodic node, which could negatively impact the tensile strength of long bamboo samples. Surprisingly when a node was included in the materials, we found that it promoted the flexural strength of the bamboo samples, leading to a higher flexural strength of up to 553 MPa (Figures S19 and S20, Supporting Informa- tion). Overall, our densified bamboo displayed superior tensile strength combined with excellent flexural strength as a compet- itive candidate to other fiber reinforced polymer composites in a variety of applications[40] (Table S3, Supporting Information).