Papathanasiou Thanasis D, Diakonikolis Michalis, Tsiantis Andreas
Department of Mechanical Engineering, University of Thessaly, 38334 Volos, Greece.
Materials (Basel). 2023 Feb 17;16(4):1691. doi: 10.3390/ma16041691.
Composite films of a graded miscrostructure hold the promise of achieving optimal use of the filler material, resulting in composites with improved and application-taylored properties. In the context of barrier materials in which the reinforcing phase comes in the form of flakes or platellets, concentrating the filler particles in certain critical regions is thought to achieve economy in filler usage while ensuring superior barrier performance. The objective of the present article is to quantitatively test this hypothesis and provide guidelines on the expected barrier improvement. A model is developed, according to which a graded miscostructure in a composite film offers a quantitative improvement over an equivalent homogeneous microstructure; this improvement is quantified using a coefficient β, which depends on the form of the graded miscrostructure, specifically the distribution of the number-density of the filler particles across the film. It is shown that β=1 for a uniform microstructure and β>1 for a graded one, indicating that a graded miscrostructure will indeed result in improved barrier properties. Analytical expressions for β are developed for certain typical distributions; for a linear filler distribution, it is shown that β=4/3. This model is tested against detailed multi-particle simulations and is found to be in excellent agreement with computational results.
具有梯度微观结构的复合薄膜有望实现填充材料的优化利用，从而得到具有改进的、适合特定应用的性能的复合材料。在增强相为薄片或小薄片形式的阻隔材料中，将填料颗粒集中在某些关键区域被认为既能实现填料使用的经济性，又能确保卓越的阻隔性能。本文的目的是对这一假设进行定量测试，并提供关于预期阻隔性能提升的指导原则。开发了一个模型，根据该模型，复合薄膜中的梯度微观结构相对于等效的均匀微观结构在定量上有改进；这种改进用系数β来量化，β取决于梯度微观结构的形式，具体取决于填料颗粒在薄膜中的数密度分布。结果表明，均匀微观结构的β = 1，梯度微观结构的β > 1，这表明梯度微观结构确实会带来阻隔性能的提升。针对某些典型分布推导出了β的解析表达式；对于线性填料分布，结果表明β = 4/3。该模型通过详细的多粒子模拟进行了测试，发现与计算结果非常吻合。
