Abstract In this paper, composites with multi-directional ellipsoidal fillers of arbitrary aspect ratio, and an interphase layer surrounding the filler, accommodating smoothly the differences in the filler and the matrix's properties, is taken into account. Each constituent of the fiber reinforced composite (FRC) is regarded to be isotropic and linear elastic, and the property of interphase is assumed to be of power-law variation across the thickness. Based on linear hygro-thermo-elastic theory and Elshelby's theory, a novel prediction scheme for effective stiffness, coefficient of thermal expansions (CTEs) and coefficient of moisture expansions (CMEs) of FRCs with functionally graded interphase (FGI) is proposed, in which the Mori-Tanaka method and piecewise method are used and novel analytical expressions for hygro-thermo-elastic of unidirectional FRCs are obtained, respectively; afterwards, a two-step homogenization technique is performed for the filler's distribution consideration. Numerical examples and analyses indicate that the effect of the thickness and mechanical properties of FGI on the overall properties of the FRC is substantial, especially for nano-filler reinforced composites; additionally, the filler content, the aspect ratio and orientation of inclusions have considerable influences on the overall properties of the hygro-thermo-elastic of FRCs.

中文翻译：

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具有功能梯度界面的纤维增强复合材料有效湿热弹性性能的微观力学模型

摘要 本文考虑了具有任意纵横比的多向椭球填料和围绕填料的界面层的复合材料，可以平滑地适应填料和基体性能的差异。纤维增强复合材料 (FRC) 的每个成分都被认为是各向同性的和线弹性的，并且界面的特性被假定为沿厚度呈幂律变化。基于线性湿热弹性理论和 Elshelby 理论，提出了具有功能梯度界面 (FGI) 的 FRC 的有效刚度、热膨胀系数 (CTE) 和水分膨胀系数 (CME) 的新预测方案，其中使用Mori-Tanaka方法和分段方法，分别获得了单向FRC的湿热弹性新的解析表达式；之后，为了填料的分布考虑，进行了两步均化技术。数值实例和分析表明，FGI 的厚度和机械性能对 FRC 的整体性能的影响是显着的，尤其是对于纳米填料增强复合材料；此外，填料含量、夹杂物的纵横比和取向对 FRC 的湿热弹性的整体性能有相当大的影响。数值实例和分析表明，FGI 的厚度和机械性能对 FRC 的整体性能的影响是显着的，尤其是对于纳米填料增强复合材料；此外，填料含量、夹杂物的纵横比和取向对 FRC 的湿热弹性的整体性能有相当大的影响。数值实例和分析表明，FGI 的厚度和机械性能对 FRC 的整体性能的影响是显着的，尤其是对于纳米填料增强复合材料；此外，填料含量、夹杂物的纵横比和取向对 FRC 的湿热弹性的整体性能有相当大的影响。