A Strong, Tough, and Scalable Structural Material from Fast-Growing Bamboo.

Lightweight structural materials with high strength are desirable for advanced applications in transportation, construction, automotive, and aerospace. Bamboo is one of the fastest growing plants with a peak growth rate up to 100 cm per day. Here, a simple and effective top-down approach is designed for processing natural bamboo into a lightweight yet strong bulk structural material with a record high tensile strength of ≈1 GPa and toughness of 9.74 MJ m-3 . More specifically, bamboo is densified by the partial removal of its lignin and hemicellulose, followed by hot-pressing. Long, aligned cellulose nanofibrils with dramatically increased hydrogen bonds and largely reduced structural defects in the densified bamboo structure contribute to its high mechanical tensile strength, flexural strength, and toughness. The low density of lignocellulose in the densified bamboo leads to a specific strength of 777 MPa cm3 g-1 , which is significantly greater than other reported bamboo materials and most structural materials (e.g., natural polymers, plastics, steels, and alloys). This work demonstrates a potential large-scale production of lightweight, strong bulk structural materials from abundant, fast-growing, and sustainable bamboo.