纤维体积分数对 Al_2O_(3f)/ZA22 复合材料拉伸强度的影响

采用日本产ＡＧ １０ＴＡ型电子万能试验机对不同纤维体积分数的挤压铸造Ａｌ２Ｏ３ｆ／ＺＡ２２复合材料的拉伸强度进行了测定。采用Ｆｒｉｅｎｄ修正的混合律模型对纤维体积分数较小时该类复合材料拉伸强度低于基体合金强度这一现象进行了深入分析。理论分析与试验结果吻合较好。在本试验条件下,求得纤维强化临界体积分数Ｖｃｒｉｔ为２３６％,超过该值,复合材料强度高于基体强度。     

连续碳纤维增强金属基复合材料增材制造工艺

针对连续碳纤维增强金属基复合材料增材制造工艺开展系统性实验探索,研究结果表明：在对碳纤维进行表面改性后,可以实现打印过程中熔融金属基体与碳纤维的良好浸润复合;送丝速度对单道沉积路径表面质量、路径宽度及其纤维体积分数影响较大,当送丝速度为4 mm/s时,沉积路径表面质量较好,路径宽度约为1.5 mm,碳纤维体积分数约为3.43%;沉积路径搭接率对打印单层表面质量影响较大,当搭接率为50%时,单层表面质量较好;基于优化后的实验参数,实现了连续碳纤维增强金属基复合材料薄壁件以及拉伸样件的直接增材制造,薄壁件内碳纤维与金属基体形成了较好结合,而且连续碳纤维对于复合后材料的抗拉强度起到了显著增强作用.     

Mechanical Properties of Phenolic-Resin Composites Reinforced with CF/BF Interlayer Hybrid Fibers

Phenolic-resin composites reinforced with carbon fiber (CF) and basalt fiber (BF) interlayer hybrid fibers plain fabric were fabricated. The tensile strength, compressive strength and interlaminar shear strength of the prepared composites were studied. The results indicated that hybrid fibers reinforced composites possessed the advantages of both CF and BF. When resin content was 35% by volume fraction, the comprehensive mechanical performance of BF/CF reinforced phenolic resin composites reached the optimal values with the warp and weft direction tensile strength, compressive strength and interlayer shear strength being 252 MPa and 487 MPa, 105 MPa and 129 MPa, 21 MPa and 20 MPa, respectively. The scanning electron microscope (SEM) observations showed that the BF/CF hybrid fibers reinforced composites had better interfacial adhesion.     

Property of three-dimensional silica composites

Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were evaluated. The effect of the silica fiber content and treatment temperature on the flexural strength of the three-dimensional SiO2 （3-D SiO2） composites also was investigated. The SiO2 composites show good mechanical properties and excellent ablative performance. The flexural strength increases with an increase in silica fiber content, and decreases with an increase in treatment temperature. When the volume fraction of the silica fiber is 50vo1% and the treatment temperature is 700℃ the flexural strength of the composites reaches a maximum value of 78 MPa. By adding cyclohexanone surfactant, the infiltration property can be largely improved, resulting in the density of SiO2 composites increasing up to 1.65 g/cm^3. The fracture surfaces of the flexural specimens observed using SEM, show that the pseudoplasticity and the toughening mechanisms of the composites are caused by absorption of a lot of energy by interface debonding and fiber pulling out.     

碳纤维/环氧复合材料弯曲模量影响因素的研究

就环氧树脂固化条件、碳纤维体积比、加载环境温度对碳纤维 /环氧复合材料弯曲模量的影响作了系统研究 .试验结果表明 ,弯曲模量与碳纤维的体积比基本上呈线性关系 ,充分固化有利于提高碳纤维/环氧复合材料弯曲模量的稳定性 .     

Processing and properties of 2D SiC/SiC composites by precursor infiltration and pyrolysis

Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide (2D-SiC/SiC) composites were molded by stacking method and densified through precursor infiltration and pyrolysis (PIP) process. SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition (CVD) technique. Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces. Additionally, the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test. The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2% (volume fraction) and 11.1%, and 40.7% (volume fraction) and 7.5%, respectively. And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa, and 180.2 MPa and 97.2 GPa, respectively. With a proper thickness, the coating can effectively adjust the fiber/matrix interface, thus causing a dramatic increase in the mechanical properties of the composites. Foundation item: Project(NCET-07-0228) support by the New Century Excellent Talents in University     

The Smart Behavior of Cement-based Composite Containing Carbon Fibers under Three-point-bending Load

1Introduction Intrinsicconductivecementbasedcompositeshavereceivedmuchattentionduringthelastdecades,becauseoftheirinterestingpotentialapplication,suchasbeingutilizedforthenondestructionoftheintegrityofconcretestructures,electromagneticinterferenceshieldin…     

玻璃纤维增强环氧树脂单向复合材料力学性能分析

采用连续玻璃纤维与环氧树脂相复合,通过金属模压成型工艺,制备出单向玻璃纤维／环氧树脂复合材料。通过三点弯曲实验论证单向纤维对树脂基体的增强作用,从而研究不同纤维含量下复合材料的弹性模量、纵向拉伸强度、纵向压缩强度的变化趋势。结果表明：随着纤维含量的增加,复合材料的力学性能均增强,当纤维体积含量为50％时,其各项性能均较好,弹性模量为40GPa,纵向拉伸强度为1200MPa,纵向压缩模量为700MPa。此外,对复合材料的其他常用力学性能参数进行检测。     

Effect of Fiber Volume Fraction on Longitudinal Tensile Properties of SiC_f/Ti-6Al-4V Composites

The longitudinal tensile properties of SiC_f/Ti-6Al-4V composites with different fiber volume fractions were simulated by the Monte Carlo 2-D finite element model. The random distribution of fiber strength was expressed by the two-parameter Weibull function. Meanwhile, contact elements and birth-death elements were used to describe the interfacial sliding process after debonding and fiber breakage(or matrix cracking) respectively, which was realized by subroutine complied in ANSYS-APDL(ANSYS Parametric Design Language). The experimental results show that the yield stress and ultimate tensile strength of SiC_f/Ti-6Al-4V composites increase with increasing fiber volume fraction, while the corresponding strain of them is just on the contrary. In addition, almost the same failure mode is obtained in SiC_f/Ti-6Al-4V composites with various fiber volume fractions when the interfacial shear strength is fixed. Finally, the tensile strength predicted by finite element analysis is compared with that predicted by Global load-sharing model, Local load-sharing model and conventional rule of mixtures, thus drawing the conclusion that Local load-sharing model is very perfect for the prediction of the ultimate tensile strength.     

Effect of fiber volume fraction on longitudinal tensile properties of SiC<Subscript>f</Subscript>/Ti-6Al-4V composites

The longitudinal tensile properties of SiC_f/Ti-6Al-4V composites with different fiber volume fractions were simulated by the Monte Carlo 2-D finite element model. The random distribution of fiber strength was expressed by the two-parameter Weibull function. Meanwhile, contact elements and birth-death elements were used to describe the interfacial sliding process after debonding and fiber breakage (or matrix cracking) respectively, which was realized by subroutine complied in ANSYS-APDL (ANSYS Parametric Design Language). The experimental results show that the yield stress and ultimate tensile strength of SiC_f/Ti-6Al-4V composites increase with increasing fiber volume fraction, while the corresponding strain of them is just on the contrary. In addition, almost the same failure mode is obtained in SiC_f/Ti-6Al-4V composites with various fiber volume fractions when the interfacial shear strength is fixed. Finally, the tensile strength predicted by finite element analysis is compared with that predicted by Global load-sharing model, Local load-sharing model and conventional rule of mixtures, thus drawing the conclusion that Local load-sharing model is very perfect for the prediction of the ultimate tensile strength.     

Fabrication of FeAl／TiC composites through reactive hot pressing

FeAl/TiC composites were fabricated by reactive hot pressing blended elemental powders. The TiC content was varied from 50% to 80% (volume fraction) and the aluminum content in the binder phase was changed from 40% to 50%(mole fraction). The effects of these compositional changes on the densification process and mechanical properties were studied. The results show that with the increase of TiC content, densities of the composites decrease due to insufficient particle rearrangement aided by dissolution - reprecipitation reaction during hot pressing. Closely related with their porosities and defect amount, the hardness and bend strength of the composites show peak values,attaining the highest values with TiC content being 70% and 60%, respectively. Increasing the aluminum content is beneficial to the densification process. But the hardness and bend strength of the composites are reduced to some extent due to the formation of excessive oxides and thermal vacancies.     

Electrical resistance behavior of vinylester composites filled with glass-carbon hybrid fibers

Vinylester (bismethacryloxy derivative of a bisphenol-A type EP resin, VE) composites with glass-carbon hybrid fibers (CF-GF) weight fraction of 50%, were prepared by the compress molding method. The distribution of carbon fiber in the hybrids was observed by stereomicroscope. The electrical resistance behavior of the composites filled with different carbon fiber (CF) weight contents (0.5% to 20%) was studied. The experimental results show that the electrical resistance behaviors of CF-GF/VE composites are different with those of CF/VE composites because carbon fibers’ conducting networks are broken by the glass fibers in the CF-GF/VE composites. The carbon fibers distribute uniformly in the networks of glass fibers (GF) like single silk and form the semi-continuous conducting networks. Composite filled with GF-CF hybrid has a higher percolation threshold than that filled with pure CF. At that time, the resistivity of CF-GF/VE composites varies little with the temperature increasing. The temperature coefficient of resistivity in GF-CF/VE composite is less than 317 ppm and the variation of the resistivity after ten thermal cycles from 20 °C to 240 °C is less than 1.96%. Funded by the Natural Science Foundation of Hubei Province (No. 2007ABA028)     

Electromagnetic shielding and absorption properties of fiber reinforced cementitious composites

In order to investigate the electromagnetic shielding effectiveness (SE) and absorbing properties of fiber reinforced concrete, steel fiber, carbon fiber and synthetic polyvinyl alcohol (PVA) fiber reinforced concrete were researched. The results show that with the increase of fiber volume fraction, the SE and trend of frequency change of corresponding fiber reinforced concrete are enhanced. When the volume content of steel fiber is 3%, the SE of concrete is above 50 dB and its frequency is above 1.8 GHz. Moreover, in the range of 8-18 GHz, steel fiber, carbon fiber and PVA fiber all can improve the microwave absorption properties of concrete. The concrete with 0.5% carbon fiber can achieve the best absorbing property, the minimum reflectivity is about -7 dB; while steel fiber optimal volume fraction is 2%. The reflectivity curve of PVA fiber reinforced concrete fluctuates with the frequency, and the minimum value of the reflectivity is below -10 dB. The results show that fiber reinforced concrete could be used as EMI(electromagnetic interference) prevention buildings by attenuating and reflecting electromagnetic wave energy.     

全金属组元铁基块体非晶的制备与性能研究

3D打印成型碳纤维接枝碳纳米管增强热塑性复合材料的强度提高

王婼楠¹，吴海宏^1，2，郭子月³，刘春太²，申长雨²

（1. 河南工业大学 机电工程学院，郑州450001; 2.郑州大学 橡塑模具国家工程研究中心，郑州450002; 3.中山大学 数学学院（珠海）,珠海519082）

创新点说明：

1) 研究了碳纤维定量接枝碳纳米管对热塑性复合材料的界面性能及拉伸性能的影响。

2) 用3D打印模压成型的工艺方法制备了热塑性复合材料。

研究目的：

研究碳纤维表面接枝不同含量的碳纳米管对复合材料微观结构、界面性能和力学性能的影响。

研究方法：

1) 采用溶液法，通过控制碳纳米管接枝反应时间，制备不同含量碳纳米管接枝碳纤维，然后用硝酸刻蚀法，去除残留溶剂，验证了碳纳米管接枝的可靠性。用扫描电镜观察碳纤维的微观形貌，用FTIR测试碳纤维表面官能团并用XPS对碳纤维的表面官能团进行分析。

2) 用扫描电镜观察碳纤维与基体的结合情况并用接触角测量仪测试碳纤维与基体的接触角。

3) 通过 3D打印成型法成型了热塑性复合材料样条，并用扫描电镜观察碳纤维热塑性复合材料的界面微观形貌。

4) 采用万能试验机测试3D打印成型热塑性碳纤维复合材料的拉伸性能，并观察复合材料断口形貌。

结果：

1) 溶液法.扫描电镜观察发现碳纳米管在碳纤维表面均匀分布，表明碳纤维与碳纳米管之间存在较强的键合关系。但随着接枝时间的增加，碳纤维表面的碳纳米管含量逐渐增加，但达到0.4%时，出现分散不均匀现象。碳纤维表面含有上浆剂和去掉上浆剂的对比发现，无上浆剂的碳纤维表面沟壑明显，这些沟槽可以增加碳纤维的比表面积和表面能，增强了基体与碳纤维的机械相互作用。用FTIR测试碳纤维表面官能团并用XPS对碳纤维的表面官能团进行分析，结果表明，经偶联剂改性后，C=O键含量明显增加，碳纤维表面引入含氧官能团。C1，O1S峰增强，表明碳纳米管接枝到了碳纤维表面。

2) 扫描电镜结果表明，与表面未接枝碳纳米管的碳纤维相比，接枝碳纳米管的碳纤维与基体PA6具有更好的润湿性。接触角测试结果对比发现，接枝碳纳米管的碳纤维与基体的接触角，明显小于未接枝碳纳米管的。

3) 通过扫描电镜观察复合材料的界面微观形貌，结果表明：纤维与基体之间存在一定厚度的界面层，界面层的存在可以减轻纤维与基体之间的力学性能突变引起的应力集中，并防止界面缺陷的扩展。

4）界面结合强度测试结果表明，当碳纳米管的质量分数增加到0.25%时，复合材料的界面结合强度比未接枝碳纳米管的碳纤维增强的PA6复合材料提高了20%，比表面有环氧的碳纤维复合材料提高了41.8%。然而当碳纳米管含量大于0.4%时，界面结合强度不再继续增加。力学测试表明碳纳米管含量为0.25%的复合材料具有最高的平均模量、拉伸强度和界面剪切强度。接枝碳纳米管的碳纤维复合材料断口形貌可以观察到界面处基体中的韧窝。表明基体树脂在拔出纤维前经历了较大的塑性变形，表明纤维与基体有很好结合性。

结论：

实验结果表明，碳纳米管可以提高表面的润湿性和CF表面粗糙度。碳纳米管接枝碳纤维增强PA6与环氧上浆的碳纤维复合材料相比，当碳纳米管的质量分数达到0.25%时，复合材料的界面结合强度增加了41.8%，拉伸强度提高了130%，界面剪切强度提高了238%。然而，随着碳纳米管含量的继续增加到0.4%时，界面结合强度和力学性能就会下降。

关键词：热塑性复合材料，界面结合强度，界面剪切强度，3D打印成型

     

混杂纤维混凝土拌合物工作性能试验研究

通过CF40,CF50,CF60混杂纤维混凝土拌合物的工作性能试验,研究了钢纤维体积分数和聚丙烯纤维掺量对不同强度混杂纤维混凝土拌合物的影响.试验中,钢纤维体积分数为0.0%,0.5%,1.0%,1.5%,2.0%,聚丙烯纤维掺量为0.0,0.6,0.9,1.2 kg/m3,并考虑包裹钢纤维的水泥浆厚度为1.0 mm.结果表明:CF40,CF50混杂纤维混凝土拌合物的坍落度呈现出随钢纤维体积分数增大而降低的变化规律,CF60混杂纤维混凝土拌合物的坍落度呈现出随钢纤维体积分数增大而先降后增再降的变化规律;在钢纤维体积分数不变时,随着聚丙烯纤维体积分数的增大,混杂纤维混凝土拌合物的坍落度降低.     

短切芳纶纤维增强水泥砂浆准静态下力学性能研究

采用二步法制备不同纤维掺量的短切芳纶纤维增强水泥砂浆试样,研究添加剂羧甲基纤维素钠(CMC)和硅微粉对复合材料力学性能的影响.结果表明:羧甲基纤维素钠能够有效地促进纤维在水中的分散,进而促进其在水泥砂浆中的分散;掺加一定量的硅微粉能够进一步提高试样的压缩强度.当纤维体积分数为5％时,试样的力学性能最好,弯曲强度从2.6 MPa提高到了8.3 MPa,压缩强度也从29.5 MPa提高到了54.3 MPa.     

凝固偏析对氧化铝/铝-铜合金复合材料性能的影响

利用挤压铸造技术制备氧化铝／铝-铜合金复合材料，研究了凝固偏析对复合材料机械性能的影响．结果表明：复合材料在凝固过程中由于选择结晶，基体中的溶质元素偏聚在纤维／基体界面或晶界上；纤维加速了复合材料的时效强化过程，随着纤维体积分数的增加，复合材料的硬度、强度、弹性模量增大，而塑性下降；随着预制件预热温度的升高，冷却速度减慢，凝固偏析加剧，复合材料的机械性能下降．     

碳纤维和尼龙纤维对TiAl合金型壳退让性的影响

为了改善TiAl合金精密铸造用氧化锆陶瓷型壳的退让性,利用电子万能试验机和扫描电子显微镜对添加不同含量碳纤维和尼龙纤维后的型壳退让性进行了测试.结果表明,添加少量碳纤维可以提高型壳湿强度并降低型壳室温和高温干强度,但当所添加碳纤维的质量分数达到10%后,会同时提高型壳的三种强度.当尼龙纤维的质量分数处于10%以内时,型壳三种强度均会降低.当碳纤维的质量分数达到5%时,型壳的湿强度和室温干强度可分别提高51. 9%和20. 7%,高温干强度降低8. 5%,同时改善了型壳的退让性并降低了铸件的裂纹倾向.     

以[Gly]Cl离子液体为溶剂制备壳聚糖纤维

以甘氨酸和36％盐酸为原料合成出甘氨酸盐酸盐离子液体,并采用间歇碱处理方式对壳聚糖原料进行处理,制备出高脱乙酰度壳聚糖.将高脱乙酰度壳聚糖溶解于离子液体的水溶液中制备出合适黏度的纺丝液,经湿法纺丝将其纺制成纤维,再对纤维进行一定程度的表面交联,可得到较好力学性能的壳聚糖纤维.结果表明,壳聚糖的质量分数(相对于3％离子液...     

SFRC subjected to domestic sewage and sustained load

The article aimed to study the durability of steel fiber reinforced concrete under the coupled sewage-loading according to compressive strength,flexural strength,compressive strength corrosion coefficient,flexural strength corrosion coefficient,compressive strength balance coefficient,flexural strength balance coefficient.Through the homemade load frame applied to design specimens,the pre-loading level are equivalent the damage intensity of 0%,10%,30% and 50% four different ways.The experimental results show that the performance of concrete down gradually and sustaining load aggravated the degree of domestic sewage attacking concrete after six month;under different stress states,the more loading levels,the more serious domestic sewage attacked the steel fiber reinforced concrete.It is proved that the concrete damage can be inhibited by adding the steel fiber,when steel fiber volume fraction is 1.0%,the corrosion resistance of concrete is best.