纳米Al2O3改性玻璃纤维增强复合材料低温力学性能研究

简述了纳米Al2O3改性玻璃纤维增强环氧树脂基复合材料的制备,并对其常温、低温力学性能进行实验。结果表明,常温、低温下,复合材料的力学性能随着纳米Al2O3含量的增加都呈现先增强后减弱的趋势。低温处理使复合材料的力学性能得到提升,并且低温下Al2O3的引入对复合材料强度的改善效果比常温下明显,Al2O3含量为1%(质量分数)时,拉伸强度提高比例高达16.61%。其原因是低温下基体强度增大,另外基体热膨胀系数大,收缩明显,界面粘接强度增大,纳米Al2O3颗粒在界面处与树脂基体结合更深入,从而使纳米粒子阻碍微裂纹扩展的能力更强。     

Enhancement of tensile and thermal properties of epoxy nanocomposites through chemical hybridization of carbon nanotubes and alumina

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid carbon nanotube–alumina (CNT–Al₂O₃) filler, via chemical vapour deposition and a physically mixed CNT–Al₂O₃ filler, at various filler loadings (i.e., 1–5%). The tensile and thermal properties of both nanocomposites were investigated at different weight percentages of filler loading. The CNT–Al₂O₃ hybrid epoxy composites showed higher tensile and thermal properties than the CNT–Al₂O₃ physically mixed epoxy composites. This increase was associated with the homogenous dispersion of CNT–Al₂O₃ particle filler; as observed under a field emission scanning electron microscope. It was demonstrated that the CNT–Al₂O₃ hybrid epoxy composites are capable of increasing tensile strength by up to 30%, giving a tensile modulus of 39%, thermal conductivity of 20%, and a glass transition temperature value of 25%, when compared to a neat epoxy composite.     

The effect of interfacial state on the thermal conductivity of functionalized Al2O3 filled glass fibers reinforced polymer composites

Rapidly increasing packaging density of electronic devices puts forward higher requirements for thermal conductivity of glass fibers reinforced polymer (GFRP) composites, which are commonly used as substrates in printed circuit board. Interface between fillers and polymer matrix has long been playing an important role in affecting thermal conductivity. In this paper, the effect of interfacial state on the thermal conductivity of functionalized Al₂O₃ filled GFRP composites was evaluated. The results indicated that amino groups-Al₂O₃ was demonstrated to be effective filler to fabricate thermally conductive GFPR composite (1.07 W/m K), compared with epoxy group and graphene oxide functionalized Al₂O₃. It was determined that the strong adhesion at the interface and homogeneous dispersion of filler particles were the key factors. Moreover, the effect of interfacial state on dielectric and thermomechanical properties of GFRP composites was also discussed. This research provides an efficient way to develop high-performance GFRP composites with high thermal conductivity for integrated circuit packaging applications.     

Investigations on NiAl composites fabricated by matrix coated single crystalline Al2O3-fibers with and without hBN interlayer

The intermetallic compound NiAl has excellent potential for high temperature structural applications but suffers from low temperature brittleness and insufficient high temperature strength. One way to remove these deficiencies is the reinforcement by high strength ceramic fibers. Such intermetallic matrix composites can be conveniently fabricated by the hot pressing of matrix coated fibers. Al₂O₃ single crystal fibers show excellent chemical stability with the NiAl matrix, but the residual thermal compressive stresses during cool down dramatically degrades the fiber strength and thus, renders the composite useless for structural applications. We report on an experimental and computational study to mitigate this problem and to fabricate Al₂O₃/NiAl composites with sufficient high temperature strength. Analytical TEM, mechanical testing and push-out tests were employed to characterize chemistry, microstructure and mechanical properties of the composites. It will be shown that a processing window exists that allows producing intermetallic matrix composites with promising mechanical properties.     

Effect of Al2O3 particle size on vacuum breakdown behavior of Al2O3/Cu composite

In order to clarify the effect of Al₂O₃ particle size on the arc erosion behavior of the ceramic-reinforced Al₂O₃/Cu composite, Al₂O₃/Cu composites with different sizes of Al₂O₃ particles were prepared by powder metallurgy, the effect of Al₂O₃ particle size on the characteristics of arc motion was studied, and the mechanism of arc erosion of Al₂O₃/Cu composites was discussed as well. The results show that with decrease in the size of Al₂O₃ particles, the erosion area increases significantly and the erosion pits become shallower. The vacuum breakdown is preferred to appear in the area between Al₂O₃ particle and the copper matrix. Based on the experimental results and theoretical analysis, a particle partition arc model is proposed.     

Refinement of microstructure and improvement of mechanical properties of Al/Al2O3 cast composite by accumulative roll bonding process

Some important problems associated with cast metal matrix composites (MMCs) include non-uniformity of the reinforcement particles, high porosity content, and weak bonding between reinforcement and matrix, which collectively result in low mechanical properties. Accumulative roll bonding (ARB) process was used in this study as a very effective method for refinement of microstructure and improvement of mechanical properties of the cast Al/10 vol.% Al₂O₃ composite. The average particle size of the Al₂O₃ was 3 μm. The results revealed that the microstructure of the composite after eleven cycles of the ARB had an excellent distribution of alumina particles in the aluminum matrix without any noticeable porosity. The results also indicated that the tensile strength and elongation of the composites increased as the number of ARB cycles increased. After eleven ARB cycles tensile strength and elongation values reached 158.1 MPa and 7.8%, which were 2.54 and 2.36 times greater than those of the as-cast MMC, respectively.     

Effect of Nb2O5 on the microstructure and mechanical properties of TiAl based composites produced by hot pressing

In situ composites of TiAl reinforced with Al₂O₃ particles are successfully synthesized from an elemental powder mixture of Ti, Al and Nb₂O₅ by the hot-press-assisted reaction synthesis (HPRS) method. The as-prepared composites are mainly composed of TiAl, Al₂O₃, NbAl₃, as well as small amounts of the Ti₃Al phase. The in situ formed fine Al₂O₃ particles tend to disperse on the matrix grain boundaries of TiAl resulting in an excellent combination of matrix grain refinement and uniform Al₂O₃ distribution in the composites. The Rockwell hardness and densities of TiAl based composites increase gradually with increasing Nb₂O₅ content, and the flexural strength and fracture toughness of the composites have the maximum values of 634 MPa and 9.78 MPa m^1/2, respectively, when the Nb₂O₅ content reaches 6.62 wt.%. The strengthening mechanism was also discussed.     

Investigation of erosive wear behavior and physical properties of SGF and/or calcite reinforced ABS/PA6 composites

The aim of this study was to investigate the erosive wear behavior of glass fiber, CaCO₃ particle and glass fiber/CaCO₃ hybrid reinforced ABS/PA6 blend based composites. The samples were prepared by using melt mixing and injection molding techniques. The mechanical, thermal, morphological properties and erosive wear behavior were investigated in terms of reinforcing agent type and composition. It was observed that the tensile strength and modulus values of hybrid composites gave a value between tensile strength and modulus values of only fiber reinforced composites and only particle reinforced composites. From DSC analysis it was revealed that T_g and T_m of composites were not significantly affected by reinforcement; however, degree of crystallinity was found to be sensitive to reinforcement type and composition. The impingement angle was found to have a significant effect on the erosive wear behavior. The results indicated that composite materials exhibited maximum erosion rate at impact angle of 30° conforming their ductile erosion behavior. In order to investigate wear mechanisms, eroded surface analysis was done by scanning electron microscopy. Surface analysis showed that repeated impact of hard silica sand particles caused a local removal of the matrix from the fiber surface and led to form craters on the surface of the composite material.     

The cryogenic thermal expansion and mechanical properties of plasma modified ZrW2O8 reinforced epoxy

In this article, epoxy resin reinforced by negative thermal expansion material, ZrW₂O₈, was fabricated. The surface modification of ZrW₂O₈ particles was performed via plasma enhanced chemical vapor deposition (PECVD) process. As a result, a thin film was uniformly deposited on the surfaces of the ZrW₂O₈ particles, leading to an improvement of compatibility and dispersion of ZrW₂O₈ fillers inside epoxy matrix. Moreover, the coefficients of thermal expansion (CTEs) of the composite material containing 0-40 vol.% fillers were studied under cryogenic temperatures. The results showed a significant reduction in thermal expansion with increasing ZrW₂O₈ content. The cryogenic mechanical properties of ZrW₂O₈/epoxy composites were also investigated, showing the properties were improved by adding ZrW₂O₈ to certain content. In addition, the mechanical strength and modulus of the composite were observed significantly higher at cryogenic temperature than that at room temperature because of the thermal shrink effect and the frozen epoxy matrix.     

Joining of SiC fibre reinforced borosilicate glass matrix composites to molybdenum by metal and silicate brazing

The brazing of SiC fibre reinforced borosilicate glass matrix composites with Mo plates has been investigated. Molybdenum was chosen as the metallic partner under consideration of system requirements, e.g. thermomechanical stability at temperatures of interest (500–750^∘C), and physical properties, e.g. coefficient of thermal expansion close to that of the glass matrix composite. Two brazing filler materials were investigated: a glass braze (Schott G018-174) and an active filler metal (Incusil ABA, brazing temperature = 740^∘C). When using the glass braze the surface of the metal had to be roughened to ensure a bond of significant strength. Vacuum brazing with the active filler metal resulted in joints with high strength, which allows to fully utilise the mechanical competence of the glass matrix composite when the joint configuration is adapted to the relevant loading conditions. A novel design of a tool for hot glassware handling, made of glass matrix composite/Mo joints, is presented.     

Effects of Al2O3 particle reinforcement on the lubricated sliding wear behavior of ZA-27 alloy composites

The present investigation deals with the effect of Al₂O₃ particle reinforcement on the lubricated sliding behavior of ZA-27 alloy. The composites with 3, 5, and 10 wt% of Al₂O₃ particles were produced by the compocasting procedure. Tribological properties of alloy and composites were studied, using block-on-disk tribometer at different specific loads and sliding speeds. The test results revealed that composite specimens exhibited significantly lower wear rate, but higher coefficient of friction than the matrix alloy specimens in all the combinations of applied loads and sliding speeds. The improved antiwear characteristics of the composites were influenced by positive effects of higher frictional heating on compatibility of the composite phases and suppressing micro-cracking tendency. Due to that, effects of reinforcing hard particles were manifested through the reduced wear rate of composites, especially in conditions of higher load, lower sliding speeds and higher Al₂O₃ particle content. In present wear tests, the significant forming of mechanically mixed layers was not noticed, what is confirmed by the SEM microphotographs.     

Preparation and properties of polyamide 6 thermal conductive composites reinforced with fibers

The majority of inorganic particles-filled thermal conductive composites highlight thermal conductivity in detriment of mechanical properties. In this work, magnesium hydroxide (Mg(OH)₂), alumina (Al₂O₃) and flake graphite-filed polyamide 6 (PA6) composites prepared by twin-screw extruder, were reinforced with carbon and glass fibers separately. Effects of fiber type and content on thermal conductivity, mechanical properties and heat deflection temperature (HDT) of the PA6-based composites were investigated. The results showed that the thermal conductivity of the composites improved with increasing carbon fiber content, while decreased slightly with glass fiber loading. Furthermore, strength, modulus and HDT of the PA6-based composites increased with the increase of fiber content. The reinforcing effects of the two fibers on the thermal and mechanical properties of the composites were compared and interpreted in this paper. By incorporating simultaneously high thermal conductive fillers and high-strength fibers, the combined composites hold a good potential in heat dissipation applications.     

Influence of SiC, Si3N4 and Al2O3 particles on the structure and properties of electrodeposited Ni

The structure and properties of electrodeposited nickel composites reinforced with inert particles like SiC, Si₃N₄ and Al₂O₃ were compared. A comparison was made with respect to structure, morphology, microhardness and tribological behaviour. The coatings were characterized with optical microscopy, Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) technique. The cross-sectional microscopy studies revealed that the particles were uniformly distributed in all the composites. However, a difference in the surface morphology was revealed from SEM studies. The microhardness studies revealed that Si₃N₄ reinforced composite showed higher hardness compared to SiC and Al₂O₃ composite. This was attributed to the reduced crystallite size of Ni — 12 nm compared to 16 nm (SiC) and 23 nm (Al₂O₃) in the composite coating. The tribological performance of these coatings studied using a Pin-on-disk wear tester, revealed that Si₃N₄ reinforced composite exhibited better wear resistance compared to SiC and Al₂O₃ composites. However, no significant variation in the coefficient of friction was observed for all the three composites.     

Influence of Fiber Orientation and Fillers on Low Velocity Impact Response of the Fabric Reinforced Epoxy Composites

The low velocity impact response of the epoxy composite materials, which were reinforced with various hybrid contents, such as plain pure or hybrid fabrics (carbon, aramid and glass fibers and copper wires) and filler mixtures into the epoxy matrix (aramid powder, potatoes starch, barium ferrite and carbon black) was investigated using a drop weight impact machine. The aim of this study was to characterize and assess the effects of fiber orientation at various angles and filler mixtures into epoxy matrix on the impact response. All the tests were carried out at constant impact energy, namely 90.629 J. Results indicated that the fiber orientation at various angles has a positive effect on impact response, mainly in the case of aramid fabric reinforced composites. In terms of influence of fillers addition into matrix, it was obtained an improvement on the impact response of hybrid fabric reinforced composite as compared to the pure fabric reinforced composites.

     

废旧线路板粉料/玻璃纤维增强复合材料研制

以废旧线路板回收处理过程中得到的塑料粉料与玻璃纤维作为增强材料,采用模压成型的方法制备成不饱和聚酯复合材料。研究了模压工艺参数以及废弃物粉末填料配比等对复合材料力学性能的影响规律,并初步展望了废弃物复合材料的应用。结果表明,随着模压温度、压强、模压时间和填料含量的增加,复合材料的弯曲强度先升高后降低;在优化的模压工艺参数条件下,用废弃粉体与短切玻璃纤维作为组合增强体,制得的不饱和聚酯复合材料的力学性能远大于仅用废弃粉体作为增强体的力学性能,其弯曲强度和冲击强度可达150MPa、18kJ/m2。     

Nano-sized aluminum oxide reinforced commercial casting A356 alloy matrix: Evaluation of hardness,wear resistance and compressive strength focusing on particle distribution in aluminum matrix

Achieving a uniform distribution of reinforcement within the matrix is a challenge which impacts directly on the properties and quality of the composite material. In the present study a fabrication and evaluation approach was used focusing on particle distribution in metal matrix. Al and Cu powders were separately milled with nano-Al₂O₃ particles and incorporated into A356 alloy via vortex method to produce cylindrical A356/nano-Al₂O₃ composites. The stirring was carried out in various durations. The variations of density, hardness, compressive strength, and wear resistance were measured throughout the cylindrical samples. The evaluation of mechanical properties and microstructural studies showed that an increase in stirring time led to a more uniform dispersion of particles in the matrix and also led to a decrease in mechanical properties due to an increase in porosity content of the composites compared with those of the samples stirred for shorter durations. Moreover, milling process affected particle distribution. Nanoparticles more uniformly dispersed in the Al₂O₃–Cu reinforced samples compared with that of the samples reinforced with Al₂O₃–Al or pure alumina powders.     

Properties of calcium copper titanate and barium titanate filled epoxy composites for electronic applications: effect of filler loading and hybrid fillers

Inorganic ceramics such as calcium copper titanate, CaCu₃Ti₄O₁₂ (CCTO) and barium titanate (BaTiO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler types and loading range on the dielectric, tensile, morphology, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin film composites with 20 vol% filler loading of CCTO and BaTiO₃ showed good dielectric properties, thermal stability, and thermal conductivity. However, the tensile properties of the CCTO/epoxy thin film composite was reduced as the filler loading increased. On the other hand, the tensile properties of BaTiO₃/epoxy thin film composite improved as the filler loading increased. Hybrid fillers CCTO and BaTiO₃ filled epoxy composites were fabricated and the effect of hybrid fillers on the dielectric properties and morphology of the epoxy thin film composites were investigated. Results indicated that positive hybrid effect in dielectric constant and dielectric loss showed by the hybrid composites.     

Equicohesive temperature of the interface and matrix and its effect on the tensile plasticity of Al18B4O33 whiskers reinforced aluminum composite at elevated temperatures

A pure aluminum composite reinforced by Al₁₈B₄O₃₃ whiskers was fabricated by a squeeze casting technique. In the present study, it is found that the dependence of tensile plasticity on temperature in Al₁₈B₄O₃₃ whiskers reinforced aluminum composite is different from other discontinuously reinforced aluminum composites. The tensile elongation to fracture of the composite obtains its maximum value at about 573 K, which is considered to be related to the equicohesive temperature of interface and matrix. This will also establish a basis for the research of hot forming process of the composite at elevated temperatures.     

Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites

Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T_g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.     

The influence of nano/micro hybrid structure on the mechanical and self-sensing properties of carbon nanotube-microparticle reinforced epoxy matrix composite

Nano/micrometer hybrids are prepared by chemical vapor deposition growth of carbon nanotubes (CNTs) on SiC, Al₂O₃ and graphene nanoplatelet (GNP). The mechanical and self-sensing behaviors of the hybrids reinforced epoxy composites are found to be highly dependent on CNT aspect ratio (AR), organization and substrates. The CNT–GNP hybrids exhibit the most significant reinforcing effectiveness, among the three hybrids with AR1200. During tensile loading, the in situ electrical resistance of the CNT–GNP/epoxy and the CNT–SiC/epoxy composites gradually increases to a maximum value and then decreases, which is remarkably different from the monotonic increase in the CNT–Al₂O₃/epoxy composites. However, the CNT–Al₂O₃ with increased AR ⩾ 2000 endows the similar resistance change as the other two hybrids. Besides, when AR < 3200, the tensile modulus and strength of the CNT–Al₂O₃/epoxy composites gradually increase with AR. The interrelationship between the hybrid structure and the mechanical and self-sensing behaviors of the composites are analyzed.