四脚氧化锌晶须/氢化环氧树脂形状记忆复合材料的制备与性能EI北大核心CSCD

采用不同比例的四脚氧化锌晶须(T-ZnOw)与氢化环氧树脂(H-EP)共混,在聚丙二醇二缩水甘油醚(PPGDGE)和异佛尔酮二胺用量不变的前提下,经完全固化制备出一种新型的复合材料。通过动态力学性能测试、力学测试、红外光谱、扫描电子显微镜和U型形状记忆测试系统地研究了该体系的力学性能和形状记忆性能。实验结果表明,该体系复合材料的玻璃化转变温度最高可达到61.5℃,其力学性能比纯环氧树脂提高了15.87%。该试样具有良好的形状记忆性能,变形的试样几乎可以完全回复。     

多官能度酚醛环氧树脂的合成表征及性能

苯甲醛和对羟基苯甲醛分别与双酚A反应,得到侧链含刚性苯环的酚醛树脂,然后环氧化,制备了侧链含刚性苯环的多官能度酚醛环氧树脂。以FT-IR1、H-NMR及GPC表征了环氧树脂的分子结构。以4,4′-二氨基二苯砜为固化剂,对环氧树脂固化物的热力学性能及热降解性能进行了研究,结果表明:由对羟基苯甲醛与双酚A反应制备的多官能度酚醛环氧树脂固化物的玻璃化转变温度、力学及耐热降解性能均比苯甲醛制备的酚醛环氧树脂固化物高,环氧树脂官能度的增加能提高环氧树脂固化物的综合性能。     

可扩链双马来酰亚胺对聚氨酯-环氧树脂基体的改性及性能表征

采用可扩链的双马来酰亚胺(BMI)和聚氨酯改性环氧树脂在4，4’-二氨基二苯基甲烷存在下固化制备了MBI改性聚氨酯-环氧树脂内部交联网络聚合物，通过红外光谱分析证实了聚氨酯在环氧骨架上的接枝，并对改性材料的力学性能、热性能和形态学进行了研究。由力学性能及热性能的研究结果表明聚氨酯与环氧树脂的复合提高了环氧树脂的机械强度，但同时也降低了玻璃化转变温度和热稳定性，而BMI与聚氨酯-环氧树脂体系的复合提高了材料的热稳定性、拉伸强度和弯曲强度，降低了材料的冲击强度和玻璃化转变温度。我们还利用扫描电子显微镜分别研究了聚氨酯改性环氧树脂和可扩链的BMI改性聚氨酯-环氧树脂体系的表面形态。     

固化温度对环氧树脂／累托土纳米复合材料的性能及微结构的影响

利用X衍射、动态力学分析（DMA）研究了不同的固化温度对环氧树脂／累托土纳米复合结构的性能及微结构的影响。实验表明，固化温度对纳米结构的形成有重要影响，在110℃以上固化时均能生成剥离型纳米复合材料；在140℃附近固化时，材料在玻璃态的储能模量最高，玻璃化转变温度也较高，此时能得到综合性能较好的复合材料。随着固化温度的提高，材料的Tg也随之提高，较高温度（高于140℃）固化时，材料的内外结构不均匀，导致力学性能变差。     

玻璃纤维/环氧树脂复合材料的微波固化行为及力学性能

采用微波固化技术,对玻璃纤维/环氧树脂复合材料进行固化试验研究,运用红外测温方法、差示扫描量热仪、力学拉伸试验机和扫描电子显微镜等试验手段分析其固化行为及微观形态,对固化试样进行了力学性能测试,并与热固化试样进行了对比。研究结果表明,微波固化能显著提高固化反应速率,相比热固化缩短了78%的固化时间;微波固化复合材料具有比热固化复合材料高的玻璃化转变温度(Tg);微波固化试样的拉伸强度能达到热固化试样的85%,而面内剪切强度却要高于热固化试样约5%。扫描电镜分析表明微波固化试样树脂基体与纤维的粘接情况要稍好于热固化试样。     

叠层法制备环氧树脂梯度交联聚合物及其性能

以α,ω-对苯甲胺基聚乙二醇、聚醚胺D400和双酚A环氧树脂(DGEBA)为原料,通过叠层法制备了玻璃化转变温度范围最大可达80℃且峰值半高宽为47.26℃的梯度聚合物材料。通过扫描电镜、拉力试验机和高级扩展流变仪研究了固化剂组分对制备的梯度交联聚合物材料结构、力学性能和阻尼性能的影响规律。结果表明,通过调整单层聚合物的交联密度即可得到适用于不同使用温度范围的宽玻璃化转变温度且力学性能优异的无微相分离结构的梯度交联聚合物材料。梯度交联聚合物tanδ>0.3的有效阻尼温域为41.54℃,且处于室温工作温度范围内。     

形状记忆氢化双酚A型环氧树脂的制备与性能

为研究聚丙二醇二缩水甘油醚(JH-230)对热固性形状记忆环氧树脂基本性能的影响,将异佛尔酮二胺(IPDA)与具有不同分子量比的氢化双酚A型环氧树脂(AL-3040)、聚丙二醇二缩水甘油醚(JH-230)共混,经完全固化制备出一种新型的形状记忆氢化双酚A型环氧树脂。借助傅里叶红外光谱仪(FT-IR)、差示扫描量热仪(DSC)、动态热机械分析仪(DMA)和拉伸-回复形状记忆测试分析了热固性形状记忆环氧树脂的分子结构以及JH-230对固化体系玻璃化转变温度、储能模量和形状记忆性能的影响。研究表明,JH-230可以增加固化体系链段的柔韧性;固化体系的玻璃化转变温度与动态模量随JH-230含量的增加而降低;该形状记忆氢化双酚A型环氧树脂体系具有良好的形状记忆性能,且形变完全回复时间随JH-230含量的增加而延长。     

微波固化环氧泡沫材料的结构和性能研究

以聚酰胺树脂、E51、E31环氧树脂为主要原料,以水为发泡剂,用微波方法制备了环氧泡沫材料,测定了环氧泡沫材料的密度和压缩性能,并对泡沫材料进行了FTIR、TGA、SEM、DMA分析.结果表明,用微波固化制备环氧泡沫材料具有高效率的特点,所制备的环氧泡沫具有优良的压缩力学性能;环氧组成对泡沫密度、泡沫结构、动态力学性能和热分解行为有较大影响.     

芳胺固化双酚S环氧树脂动态力学性质的研究

用高分子材料动态力学谱仪研究了芳香二胺固化双酚S环氧树脂（BPSER）的固化过程,讨论了固化时间,固化温度及固化剂的摩尔比等因素对固化物玻璃化温度的影响,结果表明在理论固化剂用量条件下采用变温固化过程有利于反应的控制,并可以有效提高固化产物的玻璃化温度,文中进一步研究了利用双酚S环氧树脂对双酚A环氧树脂（BPAER）／芳胺体系的改性作用,表明BPSER与BPAER／芳胺固化体系能在较宽的比例范围内很好地相容,并能显著提高固化物的玻璃化温度。     

芳胺固化四溴双酚A环氧树脂动态力学性质的研究

用高分子材料动力学谱仪研究了芳香二胺固化四溴双酚Ａ环氧树脂的固化时间,固化温度,固化剂的摩尔比,溴含量以及固化剂的种类对固化的动态力学性质的影响。通过对固化物玻璃化温度Ｔｇ的测定,为胺固化溴代环氧树脂的实际应用条件提供了理论依据。     

A multi-scale model for coupled heat conduction and deformations of viscoelastic functionally graded materials

An integrated micromechanical-structural framework is presented to analyze coupled heat conduction and deformations of functionally graded materials (FGM) having temperature and stress dependent viscoelastic constituents. A through-thickness continuous variation of the thermal and mechanical properties of the FGM is approximated as an assembly of homogeneous layers. Average thermo-mechanical properties in each homogeneous medium are computed using a simplified micromechanical model for particle reinforced composites. This micromechanical model consists of two isotropic constituents. The mechanical properties of each constituent are time–stress–temperature dependent. The thermal properties (coefficient of thermal expansion and thermal conductivity) of each constituent are allowed to vary with temperature. Sequentially coupled heat transfer and displacement analyses are performed, which allow analyzing stress/strain behaviors of FGM having time and temperature dependent material properties. The thermo-mechanical responses of the homogenized FGM obtained from micromechanical model are compared with experimental data and the results obtained from finite element (FE) analysis of FGMs having microstructural details. The present micromechanical-modeling approach is computationally efficient and shows good agreement with experiments in predicting time-dependent responses of FGMs. Our analysis forecasts a better design for creep resistant materials using particulate FGM composites.     

Transient thermal stress analysis of an edge crack in a functionally graded material

An edge crack in a strip of a functionally graded material (FGM) is studied under transient thermal loading conditions. The FGM is assumed having constant Young's modulus and Poisson's ratio, but the thermal properties of the material vary along the thickness direction of the strip. Thus the material is elastically homogeneous but thermally nonhomogeneous. This kind of FGMs include some ceramic/ceramic FGMs such as TiC/SiC, MoSi₂/Al₂O₃ and MoSi₂/SiC, and also some ceramic/metal FGMs such as zirconia/nickel and zirconia/steel. A multi-layered material model is used to solve the temperature field. By using the Laplace transform and an asymptotic analysis, an analytical first order temperature solution for short times is obtained. Thermal stress intensity factors (TSIFs) are calculated for a TiC/SiC FGM with various volume fraction profiles of the constituent materials. It is found that the TSIF could be reduced if the thermally shocked cracked edge of the FGM strip is pure TiC, whereas the TSIF is increased if the thermally shocked edge is pure SiC.     

Fabrication and mechanical properties of glass fibre–carbon fibre polypropylene functionally gradient materials

Hybrid fibre mat reinforced polypropylene (PP) composites with carbon(CF) and glass fibre (GF) were prepared and four kinds of functionally gradient materials (FGM) were fabricated by changing the spatial distribution of GF and CF. To measure the mechanical properties of FGMs and hybrid composites, flexural tests and instrumented impact tests were performed. The flexural strengths and the flexural moduli of hybrid composites increased following the rule of mixture as the relative volume content of CF increased. On the other hand, the total impact absorption energy of hybrid composites decreased with the increment of CF relative volume content. Compared with GF–CF PP isotropic hybrid composite, the composites with compositional gradient showed similar flexural strengths, but characteristic flexural moduli. Especially, sandwich-type FGMs with a CF-rich outer layer and a GF-rich inner layer exhibited higherflexural moduli than others. Total impact absorption energies of four FGMs were also similar, but the ratios of crack initiation energy,Ei, to crack propagation energy, Ep, or ductility index, were quite different.     

Fracture problems,vibration, buckling,and bending analyses of functionally graded materials: A state-of-the-art review including smart FGMS

Composite materials fail under extreme working conditions, particularly at high temperature, due to delamination (separation of fibers from matrix). And therefore it is needed to switch over functionally graded materials (FGMs) which can sustain at high temperature conditions (250–2000°C). There is a need to analyze the fracture and fatigue characteristics of FGM structures and so through this review the emphasis is given on fracture analysis of FGM materials. It has been reported that a combination of extended finite element method and isogeometric analysis methodologies has been used for general mixed-mode crack propagation problems after the introduction of extended isogeometric analysis. Furthermore, recent computational advances have been in the form of multiscale simulations where the part of model is simulated by a finer modeling scale, which can represent details of the material behavior and the interacting effects of material constituents in the finest way. The review is also focused on new advances in analytical and numerical methods for the stress, vibration, and buckling analyses of FGMs. Emphasis has been primarily on to restrict 2D analysis with sorts of compromise in the accuracy of results. First shear deformation theory (FSDT) and third-order shear deformation theory have been extensively used among the various 2D plate theories. FSDT can help us in terms of getting reasonably accurate results with less computational afford. This paper also outlines review on carbon nanotubes (CNT) reinforced FGMs, functionally graded nanocomposites, functionally graded single-walled CNT, FG nanobeam as well as functionally graded piezoelectric materials. Future applications would be based on these smart materials which are supposed to serve us in adverse conditions. Of course, with rise and advent of promising nanotechnology and its potential impact on aerospace industry as well as on other areas, it becomes important to us to compile this review article.     

Processing and characterization of functionally graded materials through mechanical properties and glass transition temperature

Functionally graded materials (FGMs) were prepared by construction based layering method through dispersion of carbon nanoparticles in the styrene butadiene rubber matrix. The gradation of material property i.e., ‘glass transition temperature’ was brought in the nanocomposite by varying the concentration of process oil. Glass transition temperature (T_g) of FGMs was varied from − 56 to − 80 °C along the span of 3 mm thick sheet. The gradation of oil in FGMs also changes other properties like tensile strength, elongation at break, modulus, etc. Tensile strength and modulus at 100% drops down while elongation at break continuously increases while moving from one end to other end along the sheet thickness. Thermal analysis of FGMs verifies the compositional changes as well as the change in T_g along the thickness.     

The fracture analysis of a graded coating/substrate system of finite thickness with arbitrary spatial variations of coating properties: Plane deformation

A new multi-layered model for functionally graded materials (FGMs) with continuously varying elastic properties is developed. The model divides the FGM into multiple layers. In each layer the material properties vary linearly and are continuous on the sub-interfaces. With this new multi-layered model, we solve the crack problems of an FGM coated strip under the in-plane deformation. The method employs the Fourier integral transform technique and singular integral equation theory. The stress intensity factors are calculated. Comparisons between the present model and other existing models show some advantages of the new model: (i) it involves no discontinuities of the material properties at the sub-interfaces; and (ii) it can be used to analyze the crack problems of FGMs with properties of arbitrary variations.     

Thermo-elasto-plastic stresses in functionally graded materials subjected to thermal loading taking residual stresses of the fabrication process into consideration

Functionally graded materials (FGMs) have recently been received with considerable interest, primarily as high temperature resistant materials for space vehicles subjected to high temperature environment. FGMs are one of the composite materials and consist of continuous change of composition of different material components from one surface to the other. FGMs usually fabricated at high temperature at which the FGMs have stress free condition. After the FGMs cooled from the fabrication temperature to the room temperature residual thermal stresses produced. In this paper, elasto-plastic thermal stresses in a rectangular plate (FGP) of a particle reinforced composite FGM are treated by finite element method due to the microscopic combination law when the FGP is subjected to three kinds of temperature conditions, first is cooling from the fabricated temperature to the room temperature, second is heating and last is heating after cooling from the fabricated temperature. In the analysis, the thermal stress constitutive equation of a particle-reinforced composite taking temperature change and damage process into consideration is used. The effects of the particle volume fraction and the three kinds of temperature conditions on the stresses in the matrix, stresses in the particle and macroscopic stress are discussed.     

Dynamic characteristics of fluid-conveying functionally graded cylindrical shells under mechanical and thermal loads

Considering rotary, in-plane inertias, and fluid velocity potential, the dynamic characteristics of fluid-conveying functionally graded materials (FGMs) cylindrical shells subjected to dynamic mechanical and thermal loads are investigated, where material properties of FGM shells are considered as graded distribution across the shell thickness according to a power-law, and dynamic thermal loads applied on the shell is considered as non-linear distribution across the thickness of the shell. The linear response characteristics of fluid-conveying FGM cylindrical shells are obtained by using modal superposition and Newmark’s direct time integration method.     

纳米SiO2/环氧树脂复合材料性能研究

采用溶液共混法制备了纳米SiO2/环氧树脂复合材料。通过冲击强度测试、SEM分析、DSC测试以及红外光谱分析、对材料的冲击性能耐热性能及其固化行为进行了探讨。实验结果表明,不同类型的纳米SiO2/环氧树脂复合材料其冲击性能都比纯环氧树脂固化物要好,并且都在纳米SiO2含量为4%时为最佳;纳米SiO2的加入也能有效提高材料的玻璃化转变温度;而且纳米SiO2的比表面积越大,其冲击性能和耐热性能越好。     

Calculation of the Composition Profile of a Functionally Graded Material Produced by Co-sedimentation

A sedimentation method is proposed to fabricate functionally graded materials (FGMs) with the continuous and smooth variations of composition .The relations between the compositional distribution of deposited body and the powder characteristics of raw materials as well as settling parameters are dervied,Subsequently ,the mathematical model of forming FGM based on the co-sedimentation has been established,At last,numerical simulations are conducted to explore the effects of the particle sizes of raw materilas and suspension height on the compositional distribution of final products.