EAGER: Dispersion and Selective Positioning of Reinforcement in Polymer Matrix Composites

由陶瓷增强材料在聚合物基质中制成的复合材料具有高强度重量比、柔韧性和缺陷容限等特点。不连续(短)纤维增强复合材料的一个优点是易于制造复杂的形状零件。然而，与连续(长)纤维增强复合材料相比，一个缺点是强度降低，这是由于在使用过程中复合材料中纤维端部的应力集中。纤维端部的这种应力局部化可能会导致基质与纤维增强体之间的粘结失效，从而导致导致材料失效的裂缝。该项目工艺的新奇之处在于，能够有选择地在纤维末端附近放置一系列颗粒尺寸，以帮助增强和分布该区域的应力。这将导致使用不连续纤维增强制造的复合材料部件具有更高的强度，有助于实现复杂几何形状部件的低成本制造。这一早期探索性研究拨款(AGER)项目将研究用于不连续纤维复合材料的胶体组装的分级陶瓷填料悬浮液的制造和分散的均质性、稳定性和重复性。据预测，这些新材料将把不连续的纤维复合材料推向提高强度和延展性的圣杯，这是大多数材料系统无法实现的组合。当这些分级组件被结合到聚合物基质中时，聚合物将渗透到组件的近界面，以形成机械硬度增强的界面区域，该界面区域围绕着更坚硬的陶瓷颗粒。这一新的视角为提高非连续纤维复合材料的性能和性能提供了一种独立于材料的方法，同时保持了与注塑、流延或热压等散装、经济和简便的制造技术的兼容性。这项研究项目将回答几个与不同成分组成的材料的应力传递和失效机制相关的基本问题，并利用新兴技术来加工具有分层形态的复合材料(即在宏观-微观和纳米制度之间进行步进)。这项工作还将提供与制造相关的挑战(即分散和准备)以及复合材料制造过程的可重复性和可靠性。

Composite materials made with ceramic reinforcements in a polymer matrix offer features of high strength-to-weight ratio, flexibility, and flaw tolerance. One advantage for discontinuous (short) fiber-reinforced composites is the ease of manufacturing complex shaped parts. One disadvantage, however, is reduced strength as compared to continuous (long) fiber-reinforced composites, due to stress concentrations at the fiber ends in the composite during use. This stress localization at the ends of fibers can lead to bond failure between the matrix and fiber reinforcement causing cracks that lead to material failure. The novelty of this project's process is the ability to selectively position a range of particle sizes near the fiber ends to help reinforce and distribute the stress in that zone. This will result in higher strength for composite parts made with discontinuous fiber reinforcement, helping to enable low cost manufacturing of parts with intricate geometries.This EArly-Grant for Exploratory Research (EAGER) project will investigate the homogeneity, stability and reproducibility for fabricating and dispersing suspensions of colloidally-assembled hierarchical ceramic fillers for discontinuous fiber composites. These new materials are predicted to push discontinuous fiber composites toward the holy grail of increased strength and ductility, a combination that is not attainable in most material systems. When these hierarchical assemblies are incorporated into a polymer matrix, the polymer will infiltrate the near-interface of the assemblies to form an interphase region of enhanced mechanical stiffness that encompasses the even stiffer ceramic particles. This new perspective offers a material independent methodology for increasing the properties and performance of discontinuous fiber composites, while maintaining compatibility with bulk, economic, and facile manufacturing techniques such as injection molding, tape-casting or hot-pressing. This research project will answer several fundamental questions associated with stress transfer and failure mechanisms for materials consisting of dissimilar components, and also take advantage of emerging technologies that enable processing of composites with hierarchical morphology (i.e., stepping between macro- micro- and nano- regimes). The work will also provide insight toward the challenges associated with fabrication (i.e., dispersion and preparation) as well as reproducibility and reliability of the composite manufacturing process.