Collaborative: Brittle Epoxies Rendered Ductile - Crazing in Thermosetting Epoxy Nanocomposites

裂纹是由高度排列的聚合物纤维桥接聚合物裂纹的现象。功能化碳纳米管的添加被发现会引发热固性环氧树脂中的起皱，而环氧树脂是一类不会出现起皱的聚合物。本项目的目的是了解通过添加功能化碳纳米管在热固性环氧聚合物中引发裂纹的机制。为此，将研究这些纳米管引起的结构变化对环氧树脂固化化学的影响。建立这些结构变化与起皱机理之间的关系。此外，还将研究多尺度静、动应力非均质性对材料力学响应的影响。控制热固性环氧树脂的起皱可以在不降低其机械强度的情况下显著提高其韧性和延展性。鉴于环氧树脂在结构应用中的广泛应用，这有望转化为重要的实际应用。这项工作的结果将为了解功能化碳纳米管添加剂在热固性环氧树脂中引发裂纹的机制提供一个基本的理解。这将导致新型纳米复合热固性聚合物的发展，这些聚合物具有显著增强的韧性、延展性和抗疲劳性，同时增强了聚合物的强度和刚度。涉及热固性环氧树脂的各种应用，如油漆，涂料，粘合剂，工业工具，复合材料以及半导体和电子封装行业将受益于这项研究。为了将研究和教学结合起来，课程以及科学博物馆的科学课程将引入专门设计的互动模块。外展活动还将包括向高中学生和教师进行实验演示和演讲。

Crazing is the phenomenon by which cracks in polymers are bridged by highly aligned polymer fibers. The addition of functionalized carbon nanotubes is found to initiate crazing in thermosetting epoxies which are a class of polymers that do not exhibit crazing. The objective of this project is to understand the mechanism by which crazing is initiated in thermosetting epoxy polymers by the addition of functionalized carbon nanotubes. To this end, the effect of structural changes induced by these nanotubes on the cure chemistry of the epoxy will be studied. The relationship between these structural changes and the mechanism of crazing will be established. Furthermore, the effect of multiscale static and dynamic stress heterogeneities on the mechanical response of the material will be studied. An ability to control crazing in thermosetting epoxies could significantly enhance their toughness and ductility without reducing their mechanical strength. Given the widespread use of epoxies in structural applications this is expected to translate into significant practical applications. The results of this work will provide a fundamental understanding of the mechanisms by which functionalized carbon nanotube additives can initiate crazing in thermosetting epoxies. This can lead to the development of a new class of nanocomposite thermosetting polymers with significantly enhanced toughness, ductility and fatigue resistance, while at the same time enhancing the strength and stiffness of the polymer. A variety of applications involving thermosetting epoxies such as paints, coatings, adhesives, industrial tooling, composites as well as the semi-conductor and electronics packaging industries will benefit from this research. In order to integrate research and teaching, specially designed interactive modules will be introduced into the curriculum as well as in the science courses taught at a science museum. The outreach activities will also include experimental demonstrations and presentations to high school students and teachers.