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力研究的既定计划（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。复合材料系统通常被过度设计，因此纤维拉伸强度的任何增加都可以显著节省成本和重量。在制造过程中对纤维表面处理（上浆）的改性是提高纤维强度的潜在途径。毫米级的单纤维拉伸测试通常用于表征上浆对纤维强度的影响。然而，复合材料的纵向拉伸破坏取决于纤维强度分布和微尺度长度处的缺陷。该奖项支持的基础研究，克服了目前的挑战，在表征纤维的拉伸强度在微观尺度上使用实验和数据驱动的计算方法。除了科学的理解，该项目还将通过受控的表面处理为纤维制造过程提供指导模板。提高抗拉强度的直接结果将是用于航空航天、汽车和运动设备领域的轻质结构。作为该项目的一部分，还将作出具体努力，通过南卡罗来纳州大学的女工程师协会从代表人数不足的群体中招募研究生和本科生。此外，本研究所建立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是难以捉摸的，并且纤维的内在强度是否遵循Weibull统计分布仍然是一个悬而未决的问题。本研究的目的是阐明在微尺度标距长度的纤维的拉伸强度的基本机制。实验和数据驱动的技术将被用来研究在微尺度上的纤维的强度分布。微尺度标距将通过在扫描电子显微镜下结合显微数字图像相关技术开发一种新的单纤维原位横向加载实验来获得。数据驱动的机器学习技术将被应用于建立强度的比例法则。该研究将为纤维上浆对纤维存活概率和强度控制机制的影响提供新的认识。这种新的加工（上浆）基础知识--结构（缺陷分布）-性质（抗拉强度分布）在微尺度长度的关系将使强度的比例定律的建立，并将作为纤维制造过程的指南，以提高纤维的拉伸强度。这一奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

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.