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Bamboo is a sustainable, lightweight material that is widely used in structural applications. To fully develop micromechanical models for plants, such as bamboo, the mechanical properties of each individual type of tissue are needed. However, separating individual tissues and testing them mechanically is challenging. Here, we report an alternative approach in which micro X-ray computed tomography (µ-CT) is used to image moso bamboo (Phyllostachys pubescens). The acquired images, which correspond to the 3D structure of the parenchyma, are then transformed into physical, albeit larger scale, structures by 3D printing, and their mechanical properties are characterized. The normalized longitudinal Young's moduli of the fabricated structures depend on relative density raised to a power between 2 and 3, suggesting that elastic deformation of the parenchyma cellular structure involves considerable cell wall bending. The mechanical behavior of other biological tissues may also be elucidated using this approach. Statement of Significance: Bamboo is a lightweight, sustainable engineering material widely used in structural applications. By combining micro X-ray computed tomography and 3D printing, we have produced bamboo parenchyma mimics and characterized their stiffness. Using this approach, we gained insight into bamboo parenchyma tissue mechanics, specifically the cellular geometry's role in longitudinal elasticity. ©2017

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references (pages 199-215)., Bamboo is a unique lignocellulosic material with considerable potential in sustainable construction. Structural bamboo products are analogous to wood products, such as oriented strand board (OSB), but composed primarily of bamboo elements, as opposed to wood elements. Such products could extend the use of bamboo. The mechanical behavior of structural bamboo products in large part depends on that of bamboo tissue. In this thesis, the structure and mechanical properties of dry bamboo tissue are related. Cellular level models are developed and explored, with a focus on density. Density is a practical parameter: it corresponds to weight, and places bamboo in the broader context of cellular solids. Bamboo tissue is made up of parenchyma and vascular bundles, consisting of sclerenchyma fibers and vessels; the structure can be thought of as a fiber reinforced composite. There is a radial gradient in the volume fraction of vascular bundles as well as the fraction of quite solid sclerenchyma fibers within the vascular bundles, increasing from the inside to the outside of the culm wall. Longitudinal flexural properties (modulus of elasticity MOE and modulus of rupture MOR) and compressive strength increase with increasing sclerenchyma fiber volume fraction, indicating the mechanical importance of these fibers. The density also increases with increasing fiber volume fraction. Thus, these longitudinal mechanical properties increase with density. This suggests that in bamboo tissue density reflects the underlying sclerenchyma fiber volume fraction. For moso bamboo (Phyllostachys pubescens), the extrapolated cell wall longitudinal Young's modulus estimate from tests on small flexural specimens, 39.8 GPa, agrees well with the value of 36.6 GPa obtained from a simple cell wall model for the fibers. From mechanical tests of 3D printed models of bamboo parenchyma, an open-cell foam model seems appropriate for bamboo parenchyma. The densification of bamboo increases the longitudinal f, by Patrick G. Dixon., Ph. D.

Background : Biological materials have a complex, hierarchical structure, with vital structural features present at all size scales, from the nanoscale to the macroscale. A method that can connect information at multiple length scales has great potential to reveal novel information. This article presents one such method with an application to the bamboo culm wall. Moso (Phyllostachys edulis) bamboo is a commercially important bamboo species. At the cellular level, bamboo culm wall consists of vascular bundles embedded in a parenchyma cell tissue matrix. The microfibril angle (MFA) in the bamboo cell wall is related to its macroscopic longitudinal stiffness and strength and can be determined at the nanoscale with wide-angle X-ray scattering (WAXS). Combining WAXS with X-ray microtomography (XMT) allows tissue-specific study of the bamboo culm without invasive chemical treatment. Results : The scattering contribution of the fiber and parenchyma cells were separated with spatially-localized WAXS. The fiber component was dominated by a high degree of orientation corresponding to small MFAs (mean MFA 11 degrees). The parenchyma component showed significantly lower degree of orientation with a maximum at larger angles (mean MFA 65 degrees). The fiber ratio, the volume of cell wall in the fibers relative to the overall volume of cell wall, was determined by fitting the scattering intensities with these two components. The fiber ratio was also determined from the XMT data and similar fiber ratios were obtained from the two methods, one connected to the cellular level and one to the nanoscale. X-ray diffraction tomography was also done to study the differences in microfibril orientation between fibers and the parenchyma and further connect the microscale to the nanoscale. Conclusions : The spatially-localized WAXS yields biologically relevant, tissue-specific information. With the custommade bench-top set-up presented, diffraction contrast information can be obtained from pl

Background Biological materials have a complex, hierarchical structure, with vital structural features present at all size scales, from the nanoscale to the macroscale. A method that can connect information at multiple length scales has great potential to reveal novel information. This article presents one such method with an application to the bamboo culm wall. Moso (Phyllostachys edulis) bamboo is a commercially important bamboo species. At the cellular level, bamboo culm wall consists of vascular bundles embedded in a parenchyma cell tissue matrix. The microfibril angle (MFA) in the bamboo cell wall is related to its macroscopic longitudinal stiffness and strength and can be determined at the nanoscale with wide-angle X-ray scattering (WAXS). Combining WAXS with X-ray microtomography (XMT) allows tissue-specific study of the bamboo culm without invasive chemical treatment. Results The scattering contribution of the fiber and parenchyma cells were separated with spatially-localized WAXS. The fiber component was dominated by a high degree of orientation corresponding to small MFAs (mean MFA 11°). The parenchyma component showed significantly lower degree of orientation with a maximum at larger angles (mean MFA 65°). The fiber ratio, the volume of cell wall in the fibers relative to the overall volume of cell wall, was determined by fitting the scattering intensities with these two components. The fiber ratio was also determined from the XMT data and similar fiber ratios were obtained from the two methods, one connected to the cellular level and one to the nanoscale. X-ray diffraction tomography was also done to study the differences in microfibril orientation between fibers and the parenchyma and further connect the microscale to the nanoscale. Conclusions The spatially-localized WAXS yields biologically relevant, tissue-specific information. With the custom-made bench-top set-up presented, diffraction contrast information can be obtained from plant tissue

Bamboo has been used structurally for thousands of years. Recently, structural bamboo products analogous to wood products have become of interest both commercially and academically. This file contains original experimental results of an investigation of both the microstructure and mechanical properties of natural Moso bamboo (Phyllostachys pubescens). One of the primary aims of the investigation is to contribute data and knowledge in order to facilitate the design of products and structures with bamboo. The authors of the dataset hope making the data available allows for easy comparison and combination with others’ results, thusly furthering this goal. The raw experimental data contained in this file is the dataset presented in the article “The Structure and Mechanics of Moso Bamboo Material” in Journal of the Royal Society Interface, with which the dataset shares a name. The data is also used in “Understanding the Structural Properties of Moso Bamboo to Engineer Sustainable Structural Bamboo Products” in the 2014 World Conference Engineering Timber Engineering Proceedings. Bamboo is known to have radial and longitudinal density gradients in the tissue. In this study, the microstructural and mechanical aspects of these gradients are the primary focus. Internodes from a single culm of Moso bamboo, obtained from Bamboo Craftsman Company (Portland, Oregon), are used. Microstructural images obtained with scanning electron microscopy (SEM) are used to determine volume fractions and solid fractions of the parenchyma and vascular bundles. These images are given in this dataset. The mechanical properties measured are: the axial Young's modulus in bending, axial modulus of rupture (in bending), axial compressive strength, and radial and tangential compressive strengths. Small mechanical test specimens (for every test type) are cut at different longitudinal (internodes) and radial positions to assess the gradients’ effects on mechanical properties. Raw data from these tests w, This dataset is based upon work supported by the National Science Foundation OISE: 1258574.