Collaborative Research: Revealing Strengthening and Toughening Mechanisms in Coconut Endocarp through Integrated Multiscale Modeling and Characterization

合作研究：通过综合多尺度建模和表征揭示椰子内果皮的强化和增韧机制

• 批准号: 2316676
• 负责人: Ning Zhang
• 金额: $ 26万
• 依托单位: Baylor University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2316676&HistoricalAwards=false
• 关键词: Collaborative; Research; Revealing; Strengthening; Toughening

Non-Technical Summary:The hard shell of the coconut, called endocarp, is a lightweight material with impressive strength, toughness, and hardness. As with many biological materials, this outstanding behavior is due to a highly complex structure. When studied at increasing magnifications, the endocarp reveals different structures at each magnification level. At the largest level, a porous network can be seen, consisting of bundles of hollow channels. Larger magnifications reveal a graded cellular structure, where larger cells are found toward the inside of the coconut, and smaller cells toward the outside. The cells themselves feature walls consisting of many layers, and each of these layers consists of tiny fibrils. Understanding comprehensively how all of these elements work together to make the coconut so strong and tough is a significant challenge, especially because of their disparity in size. This project will develop novel computer simulation techniques with the capability of treating these different elements simultaneously at the relevant sizes. This project will also develop new experimental techniques to measure and visualize directly how the different elements inside the coconut endocarp interact, to test and calibrate the computer models. This integrated computational and experimental approach will provide unprecedented insights into how the coconut’s structure gives rise to its outstanding performance. These insights and methods can then be used to engineer coconut-inspired lightweight applications that are strong and tough, for instance to improve helmets. This project will provide research opportunities to undergraduate students. For instance, computational and experimental training series will be offered to undergraduate students during the summer. Underrepresented students including female and minority students will participate in this research project. This project will also provide opportunities to students with disabilities to work on computational modeling remotely. Presentations and seminar talks will be offered to middle and high school students to attract them to participate into biomaterial research. Technical Summary:Coconut endocarp is substantially stronger and stiffer than wood, despite sharing the same major ingredients: cellulose, hemi-cellulose, and lignin. The key to this impressive mechanical performance is a sophisticated structure with many levels of structural hierarchy between the molecular scale and the macroscale. This project’s goal is to develop a rigorous understanding of the endocarp’s structure/property relationships by means of a multi-scale effort integrating novel computational and experimental techniques. A concurrent atomic-continuum (CAC) computational tool will be developed to span all relevant length scales of this materials system naturally. This approach will overcome limitations of current computational approaches, where different length scales are treated with conceptually different models that need to be interfaced. The CAC approach will be used on hierarchical materials for the first time, representing a game changing development for the materials sciences. The experimental efforts will mirror the computational work and provide characterization across all length scales. Scanning probe techniques will play a crucial role in characterizing not only the structure and mechanical properties of nano- and microscale constituents of the endocarp, but also their interfacial interactions. The outcome will be a powerful model that is calibrated and verified across multiple length scales. This model can serve as a basis to establish guidelines for bottom-up hierarchical design of synthetic cellular lightweight materials with outstanding mechanical performance, inspired by the coconut endocarp.This project is jointly funded by the Biomaterials progam (BMAT) in the division of materials research (DMR) and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术总结：椰子的硬壳，称为内果皮，是一种轻质材料，具有令人印象深刻的强度，韧性和硬度。与许多生物材料一样，这种出色的性能是由于高度复杂的结构。当研究在增加放大倍数，内果皮揭示不同的结构在每个放大水平。在最大的水平上，可以看到一个多孔网络，由成束的中空通道组成。更大的放大倍数揭示了一个分级的细胞结构，其中较大的细胞被发现朝向椰子的内部，较小的细胞朝向外部。细胞本身的特征是由许多层组成的细胞壁，每一层都由微小的原纤维组成。全面了解所有这些元素如何共同作用，使椰子如此强大和坚韧是一个重大的挑战，特别是因为它们的大小差异。该项目将开发新的计算机模拟技术，能够同时处理这些不同的元素在相关的大小。该项目还将开发新的实验技术，直接测量和可视化椰子内果皮内的不同元素如何相互作用，以测试和校准计算机模型。这种集成的计算和实验方法将为椰子的结构如何产生其出色的性能提供前所未有的见解。这些见解和方法可以用于设计椰子启发的坚固坚韧的轻量级应用程序，例如改进头盔。该项目将为本科生提供研究机会。例如，计算和实验培训系列将在夏季提供给本科生。包括女生和少数民族学生在内的代表性不足的学生将参加这一研究项目。该项目还将为残疾学生提供远程计算建模的机会。将为初中和高中学生提供演讲和研讨会，以吸引他们参与生物材料研究。 技术概要：椰子内果皮比木材更坚固，更坚硬，尽管它们具有相同的主要成分：纤维素，半纤维素和木质素。这种令人印象深刻的机械性能的关键是一个复杂的结构，在分子尺度和宏观尺度之间具有许多层次的结构层次。该项目的目标是通过多尺度的努力，结合新的计算和实验技术，发展一个严格的理解内果皮的结构/属性的关系。一个并发原子连续（CAC）的计算工具将开发自然跨越所有相关的长度尺度的材料系统。这种方法将克服目前的计算方法的局限性，在不同的长度尺度处理的概念上不同的模型，需要接口。CAC方法将首次用于分层材料，代表材料科学的游戏规则改变发展。实验工作将反映计算工作，并提供所有长度尺度的表征。扫描探针技术将发挥至关重要的作用，不仅表征内果皮的纳米和微米级成分的结构和机械性能，而且它们的界面相互作用。其结果将是一个强大的模型，在多个长度尺度上进行校准和验证。该模型可作为自下而上分层设计具有优异力学性能的合成多孔轻质材料的基础，受椰子内果皮的启发。该项目由材料研究部（DMR）的生物材料研究所（BMAT）和刺激竞争力研究的既定计划（EPSCoR）共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。