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Investigating Fundamental Toughening Mechanisms in Nanocellular Foams

研究纳米泡沫的基本增韧机制

基本信息

批准号：
2032539
负责人：
Lucas Meza
金额：
$ 85.58万
依托单位：
University of Washington
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2032539&HistoricalAwards=false
关键词：
Investigating Fundamental Toughening Mechanisms Nanocellular

项目摘要

This award supports research that will combine numerical and experimental investigations at the nano-, micro- and macroscale to uncover the mechanisms for creating tougher, lighter-weight foams using nano-sized bubbles. The light weight and energy-absorbing capacity of polymer foams makes them ideal for applications in aircraft composite panels and protective equipment like helmets, but they suffer from a fundamental problem: reducing their weight greatly reduces their strength and toughness. Recent research has shown that when the pore sizes of foams are reduced by ~1000x compared to the pores in traditional foams, their toughness can significantly increase, sometimes even exceeding that of the bulk material. This research will provide deep insight into this unexpected phenomenon by studying materials at the nano- and microscale and then using that fundamental knowledge to build models that predict and reproduce the physical properties of the foams at the macroscale. This work will have profound implications for advanced applications of polymers in bulletproof armor, synthetic leather, and tear-proof agricultural mulch films. This project also supports outreach efforts to create a Nano-Engineering of Materials and Structures (NEMS) program focused on bringing academically talented, low-income students from community colleges into a month-long program to teach them about nanomaterials and inspire them to pursue a career in engineering. The specific goal of this project is to provide a comprehensive understanding of how molecular and nanoscale architecture can couple with material size-effects to influence the macroscale properties of a nanostructured polymer. The toughness of a foam is thought to scale with the square root of its cell size, meaning nanopores would have a reduced toughness, but this theory is inconsistent with recent experiments on nanocellular foams. To provide insight into this phenomenon, the PIs will use in-situ nanomechanical experiments along with coarse grained molecular dynamics to characterize cell-level and molecular-level plasticity mechanisms. These will be incorporated with micropolar finite element models to elucidate the fracture processes occurring in nanocellular foams at the macroscale. This project seeks to answer fundamental questions of: 1) how nanoscale porosity and nanoconfinement affect molecular level plasticity, and 2) how pore-size and architecture affect fracture process zone sizes to improve toughness. Through this research, the PIs will develop a combined experimental and numerical multiscale approach to reveal the mechanics of toughness across length scales. This will lead to novel developments in tough, lightweight commercial thermoplastics and emerging engineering materials like nanocomposites.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.

该奖项支持的研究将结合联合收割机在纳米，微米和宏观尺度的数值和实验研究，以揭示使用纳米尺寸的气泡创造更坚韧，更轻的泡沫的机制。聚合物泡沫的重量轻和能量吸收能力使其成为飞机复合材料面板和头盔等防护设备的理想应用，但它们面临一个根本问题：减轻重量会大大降低其强度和韧性。最近的研究表明，当泡沫的孔径与传统泡沫中的孔相比减小约1000倍时，它们的韧性可以显著增加，有时甚至超过本体材料的韧性。这项研究将通过在纳米和微米尺度上研究材料，然后利用这些基础知识建立模型，预测和再现宏观尺度上泡沫的物理特性，从而深入了解这种意想不到的现象。这项工作将对聚合物在防弹装甲、合成革和防撕裂农业覆盖膜中的高级应用产生深远的影响。该项目还支持外展工作，以创建材料和结构纳米工程（NEMS）计划，重点是将社区学院的学术人才，低收入学生纳入为期一个月的计划，教他们纳米材料，并激励他们追求工程事业。该项目的具体目标是提供一个全面的了解分子和纳米结构如何与材料尺寸效应耦合，以影响纳米结构聚合物的宏观性能。泡沫的韧性被认为与其泡孔尺寸的平方根成比例，这意味着纳米孔将具有降低的韧性，但这一理论与最近对纳米泡孔泡沫的实验不一致。为了深入了解这一现象，PI将使用原位纳米力学实验沿着粗粒分子动力学来表征细胞级和分子级塑性机制。这些将被纳入微极有限元模型，以阐明在宏观尺度上发生在纳米泡孔泡沫的断裂过程。该项目旨在回答以下基本问题：1）纳米级孔隙率和纳米限制如何影响分子水平的塑性，以及2）孔径和结构如何影响断裂过程区域尺寸以提高韧性。通过这项研究，PI将开发一种结合实验和数值的多尺度方法，以揭示跨长度尺度的韧性机制。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。