20vol%体积分数纳米Al2O3颗粒增强铝基复合材料的高温压缩性能

为提高铝基材料的高温力学性能以满足其在573 K以上用于航空航天装备结构件的性能需求,采用高能球磨结合真空热压烧结工艺制备了体积分数高达20vol%的纳米Al₂O₃颗粒(146 nm)增强铝基复合材料,对其微观结构和高温压缩性能进行了研究。结果表明：纳米Al₂O₃颗粒均匀分散于超细晶铝基体中,且复合材料完全致密;该复合材料具有优异的高温压缩性能：应变速率为0.001/s时,473 K时压缩强度高达380 MPa,即使673 K时依然高达250 MPa,比其他传统铝基材料提高至少1倍;通过对其流变应力进行基于热激活的本构模型拟合可以发现,该复合材料具有高的应力指数(30)和表观激活能(204.02 kJ/mol)。这是由于高体积分数纳米颗粒能够有效钉扎晶界,并与铝基体形成热稳定的界面结合,显著提高复合材料的组织热稳定性,而且在变形过程中与晶界有效阻碍位错运动,显著提高复合材料的热变形门槛应力(在473～673 K时为190.6～328.4 MPa),其热变形过程可以由亚结构不变模型进行解释。     

挤压浸渗法制备Csf/Al复合材料的组织与性能

以M40石墨短纤维为增强体，LY12铝合金为基体，用挤压浸渗法制备了短碳纤维增强铝基复合材料，研究了浸渗工艺对复合材料的界面反应和组织与性能的影响，以及不同碳纤维体积分数下的常温及高温力学性能，结果表明，在冷却速度相同的情况下，浸渗温度即铝液的浇注温度对界面反应及复合材料的组织与性能影响较大，740～780℃时界面反应不明显或有轻微的界面反应，材料的性能较好．高于800℃时，碳纤维有氧化现象发生，材料的性能严重下降，甚至低于基体性能，随着碳纤维体积分数的增加，复合材料的常温及高温力学性能提高。     

基于SPS法B4C/6061Al中子吸收复合材料组织及性能

B₄C中B的同位素¹⁰B具有较大的热中子吸收截面,是良好的中子吸收体。采用放电等离子烧结法（SPS）制备了B₄C体积分数为10%~40%的B₄C/6061Al中子吸收复合材料,对B₄C/6061Al中子吸收复合材料的微观组织形貌及物相组成进行了观察分析,并测试了其拉伸性能。结果表明：B₄C颗粒均匀地分布在6061Al基体中,颗粒尖端放电产生的等离子体能够促进B₄C颗粒/6061Al基体界面结合,材料内部的物相主要有Al、B₄C、AlB₂和Al₃BC。随着B₄C体积分数的增加,B₄C/6061Al中子吸收复合材料的致密度降低,抗拉强度先增加后降低,断裂机制主要为6061Al基体及B₄C颗粒/6061Al基体界面的撕裂。     

石墨鳞片-碳纤维协同增强铜基复合材料的制备与热物理性能

采用真空热压技术制备了石墨鳞片-碳纤维协同增强铜基复合材料,研究了碳纤维含量对复合材料的组织结构、抗弯强度与热导率的影响.结果表明,石墨鳞片-碳纤维/铜基复合材料界面结合良好;当碳纤维体积分数为0.5vol％～1.5vol％时,碳纤维能够均匀分散在基体中,并有效提升复合材料的抗弯强度.当碳纤维体积分数为1.5vol％时...     

纤维预热温度对连续Al2O3f/Al复合材料力学性能的影响

选用Nextel610型Al₂O₃纤维为增强体、ZL210A连续氧化铝合金为基体,采用真空压力浸渗法制备纤维增强铝基复合材料(Al₂O_3f/Al),纤维的体积分数为40%,预热温度分别为500、530、560和600℃,研究了纤维预热温度对Al₂O_3f/Al复合材料的微观组织、纤维损伤和力学性能的影响。结果表明：随着纤维预热温度的提高复合材料的致密度随之提高,最大达到99.2%,材料的组织缺陷最少,纤维的分布均匀;随着纤维预热温度的提高从复合材料中萃取出来的Al₂O₃纤维的拉伸强度不断降低,纤维预热温度为600℃的复合材料中Al₂O₃纤维的拉伸强度仅为1150 MPa,纤维表面粗糙,有大尺寸附着物。纤维的预热温度对Al₂O_3f/Al复合材料的拉伸强度有显著的影响。预热温度为500、530、560和600℃的复合材料其拉伸强度分别对应于298、465、498和452 MPa。组织缺陷、纤维损伤和界面结合强度,是影响连续Al₂O_3f/Al复合材料强度的主要因素。     

反应热压(Al2O3+TiB2+Al3Ti)/Al复合材料的低周疲劳行为

采用反应热压法以Al、B₂O₃、TiO₂粉和Al、B、TiO₂粉为原料制备了两种(Al₂O₃+TiB₂+Al₃Ti)/Al复合材料。后一种原料粉制备的复合材料从基体中析出了细小的Al₃Ti相。研究了应变控制原位生成复合材料的室温低周疲劳行为。结果表明,在应变幅较小时(ε_</em>t≤0.3%),不含Al₃Ti析出相的材料表现为循环稳定;而在应变幅较大时(ε_</em>t≥0.4%), 则表现为第一周的循环硬化和随后的循环软化。在所采用的应变幅下,含Al₃Ti析出相的材料均表现为循环稳定。疲劳裂纹萌生部位为Al₃Ti相断裂、Al₃Ti相与基体的界面开裂和基体中微裂纹。疲劳裂纹穿过基体,绕过Al₂O₃、TiB₂质点扩展。两种复合材料的疲劳寿命均符合Coffin-Manson公式。      

化学镀镍碳纤维/环氧树脂复合材料电磁屏蔽性能

采用化学镀方法对碳纤维进行表面镀镍, 采用SEM、 EDX、 XRD分析了镀镍碳纤维的微观形貌、 镀层成分和镀层结构, 通过电阻测试研究了镀镍碳纤维的导电性。将体积分数为2.5%、 5%、 7.5%、 10%的镀镍碳纤维作为导电填料制备镀镍碳纤维/环氧树脂复合材料, 并用屏蔽室法测试了不同频段复合材料的屏蔽效能。结果表明: 碳纤维化学镀镍后, 表面形成了一层均匀的复合镀层, 镀层中镍的质量分数高达94%, 镀镍碳纤维的电阻值仅为碳纤维原丝的1/54。镀镍碳纤维/环氧树脂复合材料的电磁屏蔽能力较碳纤维原丝有所提高。复合材料的屏蔽效能随镀镍碳纤维添加量的增加而升高。在低频频段(kHz频段), 复合材料的屏蔽能力主要决定于材料的本征参数, 不同镀镍碳纤维含量的镀镍碳纤维/环氧树脂复合材料的屏蔽能力相差不大; 在中高频频段(MHz、 GHz频段), 镀镍碳纤维/环氧树脂复合材料屏蔽效能主要决定于材料的电阻率。     

溶胶-凝胶法Al2O3涂层碳纤维增强铝基复合材料的研制

以异丙醇铝为原料, 经乙酰丙酮改性, 通过水解缩合制得Al₂O₃溶胶, 研究溶胶2凝胶法在碳纤维上涂覆氧化铝陶瓷和制备(涂层) 碳纤维增强铝基复合材料预制丝的连续工艺。采用了IR、TG-DTA、XRD、SEM 等手段对溶胶2凝胶产物、涂层纤维、碳纤维增强铝预制丝进行了分析表征。结果表明: γ-Al₂O₃涂层有效的阻止了氧分子渗入, 与原纤维相比, 涂层纤维的耐高温性能明显提高。涂层后纤维与熔融铝的润湿性和相容性明显改善, 涂层有效的阻止了碳/铝界面反应, 使预制丝强度明显提高。      

化学镀镍碳纤维/环氧树脂复合材料电磁屏蔽性能

采用化学镀方法对碳纤维进行表面镀镍,采用SEM、EDX、XRD分析了镀镍碳纤维的微观形貌、镀层成分和镀层结构,通过电阻测试研究了镀镍碳纤维的导电性.将体积分数为2.5％、5％、7.5％、10％的镀镍碳纤维作为导电填料制备镀镍碳纤维/环氧树脂复合材料,并用屏蔽室法测试了不同频段复合材料的屏蔽效能.结果表明:碳纤维化学镀镍后,表面形成了一层均匀的复合镀层,镀层中镍的质量分数高达94％,镀镍碳纤维的电阻值仅为碳纤维原丝的1/54.镀镍碳纤维/环氧树脂复合材料的电磁屏蔽能力较碳纤维原丝有所提高.复合材料的屏蔽效能随镀镍碳纤维添加量的增加而升高.在低频频段(kHz频段),复合材料的屏蔽能力主要决定于材料的本征参数,不同镀镍碳纤维含量的镀镍碳纤维/环氧树脂复合材料的屏蔽能力相差不大;在中高频频段(MHz、GHz频段),镀镍碳纤维/环氧树脂复合材料屏蔽效能主要决定于材料的电阻率.     

热处理对热等静压SiP/Al-Cu复合材料显微组织和力学性能的影响

采用元素粉作为原料, 通过热等静压技术(HIP)制备出50%Si_P/Al-Cu和70%Si_P/Al-Cu(体积分数)复合材料, 研究固溶处理和峰值时效处理对复合材料显微组织、 Al₂Cu相溶解过程及力学性能的影响。结果表明: 热等静压技术制备的Si_P/Al-Cu复合材料完全致密, 组织均匀细小, 材料由Si相、 Al相和Al₂Cu组成, 白色Al₂Cu相产生于原始的Cu粉与Al粉界面处。在516 ℃固溶处理2 h后, 70%Si_P/Al-Cu复合材料中的Al₂Cu相全部溶入Al基体中, 而50%Si_P/Al-Cu复合材料中还残留少量Al₂Cu相。经过峰值时效处理后, 50%Si_P/Al-Cu和70%Si_P/Al-Cu复合材料的抗弯强度为548 MPa和404 MPa, 相对于热等静压态分别提高了38.81%和13.51%, 复合材料的强度显著增强。     

用K2ZrF6溶液处理碳化硅涂层碳纤维制造碳/铝复合丝

在碳纤维表面用CVD法涂覆碳化硅涂层,接着用K₂ZrF₆溶液处理,干燥后通过700℃的熔融铝制得碳/铝复合丝。复合丝的强度约为复合准则强度的70%。当碳纤维的体积分数为54%时,复合丝的强度达到1200MPa。用扫描电镜观察复合丝的断口发现界面结合状态良好。用X射线衍射分析了碳化硅-K₂ZrF₆一铝在高温下的反应情况,表明K₂ZrF₆的良好的改善润湿的作用是由于它与铝和碳化硅之间发生了强烈的化学反应。     

NCG Reinforced MMC Fabricated by the Squeeze Casting Method

In order to increase the wettability between carbon fiber and aluminum matrix, pure nickel was applied as coating on carbon fiber. And scanning electron microscopy was used to characterize the microstructure of the coating, fiber and matrix. The tensile tests of carbon fiber and aluminum matrix were done to examine how the behavior of nickel layers with variation of applied pressure make an effect on the mechanical properties of composites. As the applied pressure increases, nickel layers were resolved into the aluminum matrix and ultimate tensile strength of the composite decreased. This was due to premature fracture of the reaction layer acting as a surface notch.     

An investigation on the bearing test procedure for fibre-reinforced aluminium laminates

Excellent fatigue, static strength and damage tolerance characteristics together with low density make fibre-reinforced aluminium laminates a prime candidate sheet material for application in fatigue- and fracture-critical aircraft structures. Their use requires that mechanical property design allowables be established for incorporation in design handbooks (e.g. MIL-HDBK-5). An experimental programme based on statistical design was conducted to establish a meaningful test procedure for determination of fibre-metal laminate bearing strength design allowables. The test procedures investigated are the pin-type bearing test method (ASTM E-238) and the bolt-type bearing test method, a modified method based on the procedure for bearing strength determinations in plastics (ASTM D-953). Results are presented from an experimental programme which measured the bearing strengths of two grades of S-2 glass-based and one grade of aramid-based aluminium laminates. The influences of lateral constraint and ply orientation on bearing strength and failure mode are shown. The bolt-type bearing test method, which combines the attributes of the two aforementioned methods, is recommended. The study also showed that the bearing properties for edge distance ratio e/D = 2 can be predicted by correlation with the aluminium volume fraction in fibre-reinforced aluminium laminates. In addition, diagrams of joint structural efficiency, shown to be comparable to those of aluminium alloy sheets, have been established.     

Bearing strength of commingled boron/glass fiber reinforced aluminum laminates

The bearing properties of recently developed hybrid fiber/metal laminates, or COmmingled Boron/glass fiber Reinforced Aluminum laminates (COBRA), are investigated in this study. The bolt-type bearing tests on GLass REinforced aluminum laminates (GLARE), non-commingled hybrid boron/glass/aluminum fiber/metal laminates (HFML) and COBRA were carried out as a function of e/D ratio, metal volume fraction, fiber volume fraction, and fiber orientation. Experimental results show that with the same joint geometry and metal volume fraction, the commingling of boron fibers improves the bearing strength of fiber/metal laminates. Observations show the boron/glass fiber prepreg, transverse to the loading direction, results in a bearing mechanism that effectively increases the bearing strength. The bearing strength of COBRA with longitudinal fibers is lower than that with transverse fibers due to the fact that shearout failure takes place before maximum bearing strength is reached. The experimental results show that, with only either transverse fiber orientation or longitudinal fiber orientation, COBRA with 18% boron fiber volume fraction possesses a higher bearing strength when compared to HFML with 6% boron fiber volume fraction. In addition to the properties in COBRA with parallel-plies commingled prepreg, the bearing properties of various COBRA with [0°/90°] and [0°/90°/90°/0°] cross-ply commingled prepregs are also discussed.     

The effects of volume percent and aspect ratio of carbon fiber on fracture toughness of reinforced aluminum matrix composites

Carbon fiber reinforced aluminum matrix composites are used as advanced materials in aerospace and electronic industries. In order to investigate role of aspect ratio of carbon fiber on fracture toughness of aluminum matrix composite, the composite was produced using stir casting. Al–8.5%Si–5%Mg selected as a matrix. The samples were prepared with three volume fractions (1, 2 and 3) and three aspect ratios (300, 500 and 800). Three-point bending test was performed on the specimens to evaluate the fracture toughness of the materials. The results showed that the fracture toughness of composites depends on both fiber volume fraction and aspect ratio. Scanning electron microscopy (SEM) was employed to elucidate the fracture behavior and crack deflection of composites. The study also, showed that the toughening mechanism depends strongly on fiber volume fraction, aspect ratio and the degree of wetting between fiber and matrix.     

Thermal residual strains in carbon fibre-reinforced aluminium laminates

The thermal residual strains in various carbon fibre-reinforced aluminium laminates (carall), which were generated during cooling from the curing temperature, have been evaluated by both experimental methods and theoretical analysis. The experimental methods used include the deflection of an asymmetric laminate and the yield point shift of the aluminium alloy in the carall laminate. The theoretical calculation performed was based on the classical lamination theory. Residual strains determined by each experimental method and by theoretical calculation show good agreement. In addition, the possible errors associated with each method were carefully assessed and shown to be acceptable. For carall laminates reinforced with unidirectional carbon fibres, the thermal residual stress in the aluminium layer was found to be roughly proportional to the volume fraction of the carbon/epoxy layer.     

碳纤维/铝/环氧复合板的初步研究

本文揭示了碳纤维/铝/环氧复合板的显微结构,比重、热胀性能与碳纤维含量的关系,探讨了增强组份的表面处理、碳纤维/铝的叠层结构设计、碳纤维含量、纤维混杂对复合板力学性能的影响。试验表明:碳纤维/铝/环氧复合板具有轻质、低热胀、高强度等特点,当碳纤维增强环氧的含量为55vol%时,它的拉伸,弯曲与剪切强度达到或超过芳纶纤维或玻璃纤维/铝/环氧复合板的相应值。     

电镀镍碳纤维增强铝基复合材料

提出一种碳纤维表面电镀镍的方法,通过正交实验优化了电镀镍配方及工艺条件,并研究了镀层的显微组织及镀液的成分、电流密度、电镀时间等工艺条件对沉镍速率和镀层质量的影响,并探讨了沉镍机理.用镀镍碳纤维制备铝基复合材料,观测碳纤维与铝的复合效果.     

Effects of fibre/matrix adhesion on carbon-fibre-reinforced metal laminates—II. impact behaviour

Quasi-static, low-hanging and high-velocity impact tests have been conducted in order to study the effect of fibre/matrix adhesion on the impact properties of fibre-reinforced metal laminates. Differences in fibre/matrix adhesion were achieved by using treated or untreated carbon fibres in an epoxy resin system. Chemical removal of the aluminium layers and a sectioning technique were applied to examine and characterize the impact damage in the laminates. The results show that the laminates with the weaker fibre/matrix adhesion exhibit larger damage zones, although the back face crack length and permanent indentation after impact are smaller for a given impact energy. Residual tensile strength after impact is also higher for the untreated fibre laminates due to increased fibre/matrix splitting in the composite layer.     

Structurally stitched NCF CFRP laminates. Part 2: Finite element unit cell based prediction of in-plane strength

Based on experimental investigations on structurally stitched non-crimp fabric (NCF) carbon fiber/epoxy laminates under in-plane tension, compression and shear loading [1], a finite element based unit cell model was developed to estimate the in-plane strength of NCF laminates taking into consideration the yarn diameter, the stitching pattern and direction as well as the load type. Depending on these parameters, regions with undisturbed and disturbed fiber orientations leading to resin pockets as well as local changes of the fiber volume fraction are taken into account in the model.The comparison of experimental and numerical results showed that the strength of structurally stitched NCF laminates under in-plane tension, compression or shear loading can be predicted with an acceptable accuracy. The overall mean deviation between simulation and experiment observed was between 8% and 13%.