Collaborative Research: Mechanics of Hybrid Random Fiber Networks

这笔拨款将用于支持聚合物长丝随机网络力学的研究和教育，这些长丝是用硬颗粒加强的。纤维网络是许多合成材料和天然材料的主要结构成分：聚合物或生物纤维和具有刚性内含物的纳米纤维在生物组织、组织支架、生物医学植入物、静电纺空气过滤系统、纤维素产品等中无处不在。这些纤维体系大多与嵌入的非纤维实体形成复合材料。虽然连续矩阵复合材料已经得到了广泛的研究，但具有离散矩阵的混合网络的力学迄今为止还没有得到重视，尽管有大量的应用。这项研究的结果将影响纤维网络的广泛应用，如无纺布、凝胶、橡胶、组织支架、纤维素产品等的设计，以及我们对由异质随机网络组成的丰富生物系统的机械行为的理解。在教育方面，一个面向高中、本科生和研究生的计算活动和动手实验室实验的项目将包括本研究的几个方面。本研究将：(1)建立混合纤维网络的结构-性能关系；(2)将连续矩阵复合材料理论扩展到矩阵为离散纤维网络的复合材料；(3)建立实验研究纤维材料及其复合材料的新方法。连续基复合材料的理论将扩展到混杂材料，其中基体是由与主网络（基体）性能不同的颗粒或纤维增强的纤维网络。因此，将确定有效的方法来加强网络与小体积分数的填料，并伴随显著提高复合材料的刚度和强度。首先，实验和计算建模将评估孤立填料对随机网络变形场的扰动，以建立网络的等效Eshelby解。然后，探讨填料浓度对混合网络小应变、大应变力学响应和网络强度的影响，建立有效的混合网络均质化方法。使用上述系统进行的对照实验数据将用于验证数值模型，然后将用于广泛探索由网络和填料参数定义的设计空间。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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 grant will support research and education on the mechanics of random networks of polymeric filaments, which are reinforced with hard particles. Fiber networks are the main structural component of many synthetic and natural materials: polymeric or biological fibers and nanofibers with rigid inclusions are omnipresent in biological tissues, tissue scaffolds, biomedical implants, electrospun air filtration systems, cellulose products, etc. Most of these fibrous systems form composites with embedded non-fibrous entities. While continuum matrix composites have been studied extensively, the mechanics of hybrid networks with a discrete matrix has received no attention to date, despite the plethora of applications. The results of this research will influence the design of a wide range of applications of fibrous networks, such as non-wovens, gels, rubber, tissue scaffolds, cellulose products, etc. as well as our understanding of the mechanical behavior of a wealth of biological systems which are comprised of heterogeneous random networks. On the educational front, a program geared towards high school, undergraduate and graduate students with computational activities and hands on laboratory experiments will include several aspects of this research.This research will (i) establish structure-property relations of hybrid fiber networks, (ii) extend the theory of composites with continuum matrices to composites in which the matrix is a discrete fiber network, (iii) establish new methods to experimentally investigate fibrous materials and their composites. The theory of continuum matrix composites will be extended to hybrid materials in which the matrix is a fiber network reinforced with particles or fibers of different properties from those of the main network (matrix). Thereby, effective ways will be identified to reinforce networks with small volume fractions of fillers, and concomitantly improve dramatically on the composite stiffness and strength. First, experiments and computational modeling will evaluate the perturbation introduced by an isolated filler to the deformation fields of stochastic networks in order to establish an equivalent Eshelby solution for networks. Then, the effect of filler concentration on the small and large strain mechanical response and network strength will be explored to establish effective homogenization methods for hybrid networks. Data from controlled experiments performed with the aforementioned systems will be used to validate the numerical models, which will be then used to broadly explore the design space defined by the network and filler parameters.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.