Understanding the Fundamental Mechanisms Governing Tensile Strength of High-Performance Small-Scale Carbon/Glass Fibers

该项目由材料与结构力学计划和刺激竞争性研究既定计划（EPSCoR）共同资助。高性能碳纤维和玻璃纤维广泛用作汽车、航空航天和国防应用的复合材料系统的增强材料。商业纤维的拉伸强度明显低于其理论极限。复合材料系统通常经过过度设计，因此纤维拉伸强度的任何增加都可以显着节省成本和重量。在制造过程中对纤维表面处理（施胶）进行修改是提高纤维强度的潜在途径。毫米级单纤维拉伸测试通常用于表征施胶对纤维强度的影响。然而，复合材料的纵向拉伸失效受纤维强度分布和微米级长度缺陷的控制。该奖项支持基础研究，克服当前使用实验和数据驱动的计算方法在微观尺度上表征纤维拉伸强度的挑战。除了科学认识外，该项目还将通过受控表面处理为纤维制造工艺提供指导模板。提高抗拉强度的直接结果是为航空航天、汽车和运动器材领域的应用带来轻质结构。作为该项目的一部分，还将开展一项具体工作，旨在通过南卡罗来纳大学女工程师协会从代表性不足的群体中招募研究生和本科生。此外，本研究开发的实验装置将纳入本科生的实验课程中。对商业纤维的实验拉伸强度与其理论极限之间的差异的全面理解一直难以捉摸，内在纤维强度是否遵循威布尔统计分布仍然是一个悬而未决的问题。这项研究旨在阐明控制微标距纤维拉伸强度的基本机制。将采用实验和数据驱动技术来研究微观尺度上纤维的强度分布。将通过在扫描电子显微镜下结合微数字图像相关性对单纤维进行新型原位横向加载实验来获得微尺度标距长度。将应用数据驱动的机器学习技术来建立强度的缩放定律。这项研究将为受纤维尺寸影响的纤维中的存活概率和强度控制机制的功能形式提供新的见解。这种关于微尺度长度上的加工（上浆）-结构（缺陷分布）-性能（拉伸强度分布）关系的新基础知识将有助于建立强度缩放定律，并将作为纤维制造工艺提高纤维拉伸强度的指南。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project is jointly funded by the Mechanics of Materials and Structures program and the Established Program to Stimulate Competitive Research (EPSCoR). High performance carbon and glass fibers are widely used as reinforcements in composite material systems for automotive, aerospace and defense applications. The tensile strength of commercial fibers is significantly less than its theoretical limits. The composite systems are often overdesigned, thus any increase in the fiber tensile strength can yield significant cost and weight savings. Modifications of fiber surface treatment (sizing) during manufacturing is a potential route to enhance the fiber strength. Single fiber tensile testing at millimeter-scale is typically used to characterize the effect of sizing on the fiber strength. However, the longitudinal tensile failure of a composite is governed by the fiber strength distribution and defects at microscale lengths. This award supports the fundamental research that overcomes current challenges in characterizing the tensile strength of the fibers at the microscale using experimental and data-driven computational methods. Besides the scientific understanding, this project will also provide a guiding template for the fiber manufacturing process through controlled surface treatment. A direct consequence of improving the tensile strength would be lightweight structures for applications in aerospace, automotive, and sports equipment sectors. As part of this project, a specific effort will also be aimed at recruiting graduate and undergraduate students from under-represented groups through the Society for Women Engineers at the University of South Carolina. Furthermore, the experimental setup developed in this research will be incorporated into a lab course for undergraduate students.A comprehensive understanding of the discrepancy between experimental tensile strength of commercial fibers and its theoretical limits has been elusive, and whether intrinsic fiber strength follows a Weibull statistical distribution remains an open question. This research aims to elucidate the fundamental mechanisms that govern the tensile strength of fibers at microscale gage lengths. Experimental and data-driven techniques will be employed to study the strength distribution of the fibers at microscales. Microscale gage lengths will be accessed by developing a novel in situ transverse loading experiment on single fibers under scanning electron microscope combined with micro-digital image correlation. Data-driven machine learning techniques will be applied to establish the scaling laws of strength. This research will provide new insights into the functional form of the survival probability and strength-controlling mechanisms in fibers influenced by fiber sizing. This new fundamental knowledge of processing (sizing)-structure (defect distribution)-property (tensile strength distribution) relationship at microscale lengths will enable the establishment of scaling laws for strength and will serve as a guide for fiber manufacturing process to enhance the fiber tensile strength.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.