树枝状非连续界面相对碳／铝复合材料力学性能的影响

以弹塑性力学理论,断裂力学理论及非线性有限元理论为基础,根据材料实验和观察的现象及数据,采用有限元分析方法,建立了树枝状非连续界面相有限元计算模型,分析碳／铝复合材料界面反应产物对复合材料力学性能的影响,阐述了非连续界面影响材料强度的机理,并将该界面细观的不连续结构和复合材料宏观的力学性能联系起来。     

过渡区界面对混凝土劈裂性能的影响的试验与数值模拟

过渡区界面(ITZ)是混凝土三相界面中的最弱界面,对混凝土的强度有重要的影响。在实际中过渡区界面的厚度极薄,很难以实验测得其强度。为了了解它的力学性能对混凝土承载能力的影响,通过对比混凝土劈裂试验与有限元软件ABAQUS中数值模拟的方法,研究了ITZ界面的力学性能对混凝土的劈裂破坏造成的影响。结果表明:混凝土的劈裂强度随着ITZ界面强度的降低而降低;当ITZ界面的强度低于砂浆界面的50%以下时,劈裂强度会出现明显的下降。随着ITZ界面厚度的增加,劈裂强度也随之降低。粗骨料的形状会对承载能力造成影响,形状越不规则的骨料模型其承载能力越强。     

MICROMECHANICS ANALYSIS ON EVOLUTION OF CRACK IN VISCOELASTIC MATERIALS

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Two-phase displacement of non-newtonian fluid

This paper considers the problem of non-Newtonian oil displa-cement by water in porous media.adopting the linear permea-tion law with initial pressure gradient.For one-dimensionalflow,the basic equation of non-Newtonian oil displacement bywater in sandstone reservoirs and fractured reservoirs is de-rived and numerical solutions are obtained.The results arecompared with the corresponding ones for Newtonian oil dis-placement to show the essential characteristics of non-Newto-nian oil displacement by water.     

复合材料动态粘弹性能的细观研究

利用细观力学的Eshelby等效夹杂方法研究了颗粒增强复合材料的动态粘弹性力学性能,分析了材料复模量随夹杂体积分数、载荷频率之间的变化规律,给出了许多有意义的结论,为复合材料结构的优化设计及应用提供了理论基础.     

水泥砂浆界面相弹性常数的反演计算

为了计算水泥砂浆界面过渡区的弹性常数,采用广义自洽方法(GSCM),根据水泥砂浆内部的微细观结构,建立了由水泥浆基体、岩石离散夹杂(骨料)、界面过渡区(ITZ)和有效弹性材料组成的四相复合材料模型.推导了界面相的体积模量和剪切模量方程.利用已知水泥砂浆材料的实验数据,计算了界面相的弹性常数.发现界面相剪切模量约为水泥浆基体剪切模量的50%.     

金属基复合材料的蠕变与松弛

本文利用微观力学方法研究了金属基复合材料的常温蠕变和应力松弛,连续纤维在弹性粘塑性基体内单向铺设。本文的结果与实验结果符合较好。研究表明,纤维在轴向对基体的蠕变起到明显阻止作用,而在横向和剪切变形下的作用较小。在低应力水平下,复合材料的蠕变变形很小,在高应力水平时,蠕变变形明显甚至引起蠕变破坏。     

Correlation of morphological parameters and mechanical performance of polyamide‐612/poly (ethylene–octene) elastomer blends

Blends of polyamide‐612 (PA‐612) and maleic anhydride grafted poly (ethylene–octene) elastomer (POE‐g‐MA) as an impact modifier have been prepared in the composition range of 0–35 wt. % of POE‐g‐MA and subsequently investigated for their structural, thermal, mechanical, dynamic mechanical properties and morphological attributes. X‐ray diffraction studies revealed a decrease in crystallinity whereas the thermal properties such as onset to degradation temperature and crystallization temperature remained broadly unaffected. Nearly three‐fold increase in the impact strength is registered accompanied by substantial increase in tensile failure strain, though tensile modulus (E) and tensile yield strength (σ _y) decreased with increase in impact modifier content. Dynamic mechanical analysis exhibited a singularity response in the loss factor in the temperature range of ~10°C–50°C. Micromechanical aspects were analyzed using conventional theoretical models for low strain mechanical response (E) such as rule of mixtures and foam model and for high strain mechanical response (σ _y) such as Nikolais–Narkis model and porosity model. Impact toughness and strain‐at‐break of the investigated composition were successfully correlated to the domain size (D_n) of the dispersed phase and their inter‐particle distances (τ). Scanning electron microscopy showed the coalescence of domains of the dispersed phase at higher POE content and thus reiterates the crucial role of inter‐particle distance in controlling the toughening mechanism of POE blended PA‐612. Copyright © 2013 John Wiley & Sons, Ltd.     

铁电复合材料的力电耦合行为

对铁电复合材料力电耦合行为的研究进行综述．介绍了铁电复合材料的一些基本特点和线性压电有效性能的研究进展．阐述铁电复合材料中由于铁电相的铁电畴变与铁弹畴变以及基体相的弹性、粘弹性和介电弛豫性质所引起的铁电复合材料的非线性力电耦合行为．介绍了基于细观力学方法对铁电复合材料的本构关系进行研究的一些结果．     

Investigation of the three-dimensional micromechanical behavior of woven-fabric composites

A three-dimensional representative volume-element model is presented to study the micromechanical behavior of woven-fabric composites. The effects of the fiber undulation zone and the fiber braid angle on the elastic modulus of the composites are taken into account in the unit cell. Based on isostrain and isostress assumptions, a standard homogenization procedure is used to calculate the effective elastic properties of woven-fabric composites, and all the final stiffness components are expressed in an explicit form. The results obtained by the model considered agree with published experimental results very well. The relationship between the geometric parameters, such as fiber width, thickness, volume fraction, etc., and the macromechanical behavior of the composites can be obtained by this model. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 209–220, April–May, 2006.