Collaborative Research: Measurements of Yield Strength and Local Viscoelastic Properties Using Nanoparticle Embedment Methods

这项工作扩展了一种新的纳米球嵌入实验，以测量表面的屈服行为。该方法还承诺一种新的，高空间分辨率的方法来映射聚合物和复合材料的表面力学/粘弹性。这项工作建立在CMMI支持的工作基础上，其中发现小于一定尺寸的纳米颗粒沉入表面并被聚合物完全吞没。分析表明，只有当超过聚合物表面的屈服强度时，纳米颗粒才被完全吞没，这开辟了一条测量表面屈服强度以及20 nm量级深度处其他性能的途径。 如果成功的话，它也将导致一种技术，提供一个表面性质地图的机械，包括模量，屈服强度，和粘弹性的聚合物表面使用嵌入的单层的成簇的纳米粒子。 这项工作还涉及嵌入过程的数值分析，包括适当的弹塑性，粘塑性或粘弹性本构模型，以提取非线性材料特性。通过其跨学科的性质，该项目为化学工程和机械工程的学生提供了一个难得的培训机会，可以进入纳米级聚合物热机械行为的研究。此外，这是一个合作项目，研究生将有机会与来自另一个机构的学生互动，并与他们一起工作。 本专题的部分工作将被分成小专题，用于本专题中PI提供的粘弹性和聚合物物理等课程的学期专题。所有重要的结果都将发表在期刊上，以传播研究结果。预计从事该项目的研究生将在国家/国际会议上介绍他们的研究结果。

The proposed work expands a novel nanosphere embedment experiment to the measure of the yield behavior of surfaces. The method also promises a novel, high spatial resolution method to map the surface mechanical/viscoelastic properties of polymeric and composite materials. The work builds on CMMI supported work in which it was found that nanoparticles smaller than a certain size sink into the surface and become fully engulfed by the polymer. Analysis suggests that the nanoparticles are fully engulfed only when the yield strength of the polymer surface is exceeded, which opens a route to measure the surface yield strength, as well as other properties at depths on the order of 20 nm. If successful, it will also lead to a technique to provide a surface property map of mechanical, including modulus, yield strength, and viscoelastic properties of polymer surfaces using embedment of a monolayer of clustered nanoparticles. The work also involves numerical analysis of the embedment process to include appropriate elastic-plastic, viscoplastic or viscoelastic constitutive models to extract nonlinear material properties. By its interdisciplinary nature, the project provides a rare training opportunity for students in both chemical engineering and mechanical engineering to step into research in the thermo-mechanical behavior of polymers at the nanoscale. In addition, it is a collaborative project in which the graduate students will have the opportunity to interact with students from another institution and work with them. Part of the work in this project will be divided into smaller projects for use in term projects in courses such as viscoelasticity and polymer physics offered by the PIs in this project. All significant results will be published in journals to disseminate the findings. It is anticipated that the graduate students working on the project will present their findings at national/international conferences.