Rahman, Muhammad MAjayan, Pulickel M2024-08-302024-08-302024-082024-08-08August 202Thakur, Md Shajedul Hoque. Additive Manufacturing of Bio-inspired Sustainable Composites. (2024). PhD diss., Rice University. https://hdl.handle.net/1911/117806https://hdl.handle.net/1911/117806Material efficiency is a key element of sustainable development. This can be achieved by recycling and reducing material waste, as well as through innovative designs that optimize material usage. Nature has many examples of complex hierarchical designs yielding lightweight efficient structural materials. Additive manufacturing enables the fabrication of material-optimized structures and material recycling at the product’s end-of-life. Thus, addressing both aspects- sustainable materials and sustainable design. We transform waste wood into ink to facilitate the first-ever 3D printing of recyclable wood structures, and we also 3D print material efficient origami designs for the first time using a brittle material. Natural wood has long been essential in construction and furniture but traditionally wood shaping has relied on subtractive manufacturing, which leads to substantial wood waste, raising critical sustainability concerns. Herein we extract lignin and cellulose from waste wood to formulate a water-based ink that facilitates the 3D printing of wood. The printed structures, after heat treatment, closely mimic natural wood’s properties, including aesthetics and mechanical characteristics. This method also allows for incorporating reinforcements, such as natural fibers. Adding natural fibers substantially improves the mechanical properties of 3D-printed wood. iii We also add fire retardants into the wood composite, which takes the structures very close to fire-safety standards, offering a sustainable pathway for the future development of fire-resistant and recyclable 3D-printed wood structures. The ancient art of origami is attractive in modern engineering for its material- efficiency. While origami-inspired metamaterials research often focuses on flexible materials, this study investigates the use of brittle materials, with the aim to change their failure mode through origami and bio-inspired soft material coatings. A ceramic based origami structure was 3D printed and coated with a biocompatible hyperelastic polymer. Mechanical tests, both experimental and numerical simulations, revealed that the origami design imparts its anisotropic behavior to the ceramic. The hyperelastic coating distributes tensile load throughout and hinders crack propagation, increasing damage tolerance and preventing catastrophic failure. This research opens the pathway to utilizing origami engineering in brittle materials. Overall, the goal is to take a step toward sustainable materials and design through additive manufacturing of bio-inspired composites.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.3D printingSustainabilityCompositesBio-inspiredThesis2024-08-30