基于CFRP智能表层的GFRP结构变形监测

以短切碳纤维毡和环氧树脂为原材料制备CFRP复合材料,提出将其作为智能表层用于GFRP结构变形监测。实验结果表明,CFRP智能表层具有稳定的伏安性能和力阻效应,随着拉应变的增加,其电阻表现出线性的可恢复的增大,且具有较好的稳定性;利用CFRP智能表层电阻变化,无论是将其敷设在受拉侧还是受压侧,均可实时监测GFRP梁的弯曲变形;通过采用不同电极布置方式的对比试验发现,CFRP智能表层的测试结果受到电极布置方式的影响,端部电极四电极法和表面电极四电极法的力阻灵敏度分别为5.9和7.3,而两电极法的灵敏度可达到13.1,但在稳定性方面四电极法优于两电极法。     

CFRP加固钢筋混凝土梁锚固位置的试验研究

为研究混凝土梁经CFRP加固后界面粘结性能及抗弯承载力,对4根不同锚固位置的试验梁进行加载试验.结果 表明:随着锚固点的增加,试件由CFRP剥离破坏转为拉断破坏;端部锚固和中部锚固比未锚固梁极限承载力提高20.83％,延性系数提高36.84％,CFRP极限强度利用率最高达83.4％;经端部锚固后,CFRP应变范围扩大,界面粘结应力比不锚固时提高32.1％,说明端部锚固可有效降低应力集中现象,充分发挥外部加固材料的强度.     

碳纤维复合材料的电阻-应变传感特性研究

在研究碳纤维复合材料(CFRP)的电阻-应变变化规律的基础上,本文分析了碳纤维织物形式、电极种类对电阻变化的影响.并对单向碳纤维布复合材料的导电模型进行了推导.结果表明,单向碳纤维布复合材料电阻变化具有较好的应变相关性,可作为应变传感器使用,达到预警及智能监测的效果.     

无粘结预应力CFRP板加固RC梁预应力损失研究

先对碳纤维增强聚合物(CFRP)薄板施加预应力,然后再将其锚固于已受荷载的混凝土梁上,测试了CFRP板中应变变化,研究了预应力施加完成至实验梁单调加载前的预应力损失情况,并采用对数函数进行了拟合,公式的拟合结果与试验值吻合较好。结果表明,实验梁加载后,CFRP板中应变增量基本一致,可认为在加载过程中体外片材各处应变基本相等。     

CFRP拉挤板材的力阻效应

采用单向拉伸试验考察了碳纤维增强塑料(CFRP)拉挤板的电阻–应变响应规律。结果表明,纵向拉应变引起CFRP拉挤板纵向电阻的增大,其力阻效应的平均灵敏度为1.87,尺寸变化是其电阻变化的主要原因;CFRP拉挤板的力阻响应具有较好的线性,其非线性误差为±1.5%;循环加载过程中,CFRP拉挤板的力阻响应平稳,重复性误差为±4.3%;经过一个周期的加载–卸载试验后,CFRP拉挤板的电阻产生不可逆的增大,其迟滞误差为±4.8%。     

端部增强方式对CFRP管轴压力学性能的影响

端部局部破坏严重制约CFRP(Carbon Fiber Reinforced Polymer)管轴压承载力的发挥,对采用金属加强箍-金属端帽增强与碳纤维-金属内衬增强两种端部增强方式的CFRP层合管进行了轴压试验,得到了试件受力过程和破坏形式。基于Hashin失效准则,利用有限元模型分析两种端部增强方式下CFRP管首层失效模式和承载力,并解释了增强机理。研究表明:与未施加端部增强的试件相比,端部增强可改变试件失效模式并提高承载力;端部增强时,外部增强约束刚度不宜过大,增强件与试件较大的刚度差会导致变形不一致,易在增强端边缘处发生剪切破坏;采用碳纤维-金属内衬的端部增强方式可有效防止端部发生"开花式"破坏和剪切破坏,可使层合管发生整体破坏,轴压承载力提高了46.37%。     

基于数学模拟的碳纤维胶粘板剪切性能研究

采用真空辅助成型方法制备得到碳纤维增强复合材料(CFRP)胶粘板。研究了基于应力的3D-混合失效准则对CFRP胶粘板的损伤失效模型，并对应力、应变和剪切失效时的应力分布进行了数值模拟。结果表明：高温高湿老化胶粘板面内剪切达到峰值前的Mises应力分布与未老化试样的主要受力在中部区域，试样都在板材一侧发生断裂，裂纹近似呈V型。高温高湿老化不会对CFRP胶粘板的失效模式产生影响，未老化CFRP胶粘板试样的峰值荷载和剪切应力相对较大；而经过高温高湿老化处理后，CFRP胶粘板试样的承载能力和剪切应力有所降低，这与荷载-位移曲线结果和应力、应变云图结果吻合。     

复合材料篮球架CFRP/钢界面粘接性能研究

研究了不同温度复合材料篮球架CFRP板加固钢板试件的粘接性能。结果表明,温度为-20、0、15、30和45℃时,CFRP-S-20、CFRP-S0、CFRP-S15、CFRP-S30和CFRP-S45试件的极限荷载试验值分别为134.0、190.9、309.9、266.3和144.6kN,对应的破坏模式分别为CFRP与胶层剥离+胶层破坏、CFRP层间剥离+胶层破坏、胶层破坏、CFRP层间剥离+胶层破坏和钢与胶层剥离+胶层破坏。-20℃和0℃时CFRP/钢试件板面中间缺陷处的应变分布曲线的斜率较大,而15、30和45℃时CFRP/钢试件板面中间缺陷处的应变分布曲线的斜率相对更加平缓;CFRP-S-20、CFRP-S0、CFRP-S15、CFRP-S30和CFRP-S45试件板面A侧和B侧的缺陷处粘接剪应力都高于端面,且存在沿着粘接方向逐渐减小的特征。     

Si3N4/BN复合材料界面应变能释放速率的测试与表征

提出了一种更为合理、简便地测试与表征Si3N4／BN复合材料界面应变能释放速率的方法，借助流延成形和热压烧结工艺，制备出具有单一界面层“三期治”结构，在单侧基体中点处预制有裂纹源的Si3N4／BN／Si3N试样，用四点结弯曲加载的方法测出其载荷－位移曲线，进一步求出界面的应变能释放速率值，分别测出了BN＋Si3N4，BN Al2O3两种界面体系、不同成分界面的应变能释放速率值，对于纯BN，含积分数分别为15％，25％Si3N4调节的界面，其相应的应变能释放速率值分别为37．16，90．58，117．76J／m^2；含体积分数分别为16％，36％，63％Al2O3调节剂的界面，临界应变能释放速率值分别为53．95，71．86，119．21J／m^3，试验结果证明了该种方法的可行性及可靠性，与文献所报道的方法进行了对比、分析，同时分析了相关因素对实验结果的影响。     

玻璃纤维与碳纤维混合增强塑料(下)

四、混合增强塑料的性质 1.大的断裂应变 图7是CF与GF混合增强的应力-应变理论曲线(26,28)。CFRP的断裂在A点发生;因而初始模量E_1随着GFRP里CF含量增加而显著增加;GFRP的断裂点在D,因而在CFRP断裂后,第二模量E_2是较低的。所以,混合材料的应力-应变曲线可能是OABD或OACD。当环氧树脂里的碳纤维含量为40％(体积)的混合材料,实测曲线如图8(34)所示,类似图7中的理论曲线OABD。显然,在混合材料的断裂过程中,有较大的能量吸收过程,使碳纤维的“毁灭”性的脆性断裂得到了改善。     

二维编织复合材料在正交切削中的切削力和加工表面质量研究

二维编织碳纤维复合材料因其具有优异的力学性能和耐疲劳、耐冲击等特点被广泛用于制造各类复合材料结构件中。但是由于二维编织碳纤维复合材料的多相性和特殊的纤维结构,其机械加工性能与传统金属材料和单向纤维复合材料差异较大。为了研究二维编织碳纤维复合材料的切削性能,提高加工效率和加工后的表面质量,基于正交切削实验对二维编织碳纤维复合材料在切削过程中的切削力进行测试,并利用金相显微镜和粗糙度轮廓仪来表征加工表面质量。实验结果显示,正交切削过程中纤维方向角度对切削力的大小影响巨大,当切削速度提高和切削深度降低时,复合材料展现了更好的切削性能,并且加工后的表面质量更高。     

Synchronized current oscillations of formic acid electro-oxidation in a microchip-based dual-electrode flow cell

We investigate the oscillatory electro-oxidation of formic acid on platinum in a microchip-based dual-electrode cell with microfluidic flow control. The main dynamical features of current oscillations on single Pt electrode that had been observed in macro-cells are reproduced in the microfabricated electrochemical cell. In dual-electrode configuration nearly in-phase synchronized current oscillations occur when the reference/counter electrodes are placed far away from the micro-electrodes. The synchronization disappears with close reference/counter electrode placements. We show that the cause for synchronization is weak albeit important, bidirectional electrical coupling between the electrodes; therefore the unidirectional mass transfer interactions are negligible. The experimental design enables the investigation of the dynamical behavior in micro-electrode arrays with well-defined control of flow of the electrolyte in a manner where the size and spacing of the electrodes can be easily varied.     

单向碳纤维增强塑料磨削加工性能

碳纤维增强塑料因具有优异的力学性能,在航空航天等领域有重要应用。通过单向碳纤维增强塑料(CFRP)的平面磨削实验,研究了塑料增强方向对CFRP磨削加工性能的影响。研究发现,单向塑料基复合材料磨削时,由于纤维增强塑料的各向异性,磨削力与加工表面粗糙度均呈现明显的规律性。其中,在加工参数砂轮转速为1500 r/min,进给速度为5 m/min和切削深度50μm的条件下,最大和最小磨削力分别为42和10 N,而且,磨削力符合规律:法向>纵向>横向。通过对磨削加工表面显微形貌的分析,揭示了塑料基复合材料磨削微观多向材料的去除机理。研究结果不仅对拓展CFRP的应用具有重要的经济意义,同时,能够为复合材料精密加工提供一定的理论和实验支撑。     

Influence of geometric variables on the current distribution uniformity at the edge of parallel plate electrodes

In electrochemical processes, the reaction is controlled by electrodes relative placement; to many respects parallel plates seems close to the ideal configuration. However, edge effect represents a detrimental phenomenon that can compromise overall process efficiency. Cell's enclosing insulating walls can attenuate extreme current densities occurring at the electrode edge if appropriately designed to modify the current flow paths. Configurations comprising a limited counter electrode width, an enclosing normal insulating wall, an enclosing oblique insulating wall and a thin parallel mask have been studied. Potential distribution and electrical current lines of these configurations are obtained from algebra operations of complex variables owing to conformal mapping method. It was found that current distribution non-uniformity is conveniently expressed as the absolute deviation from the prescribed value. The dependence of this parameter on geometric variables can be mapped. The picture given by these maps solved the engineering problem of deducing the cell geometry complying with a given current distribution uniformity. Furthermore, optimal parameters providing the best possible performance of each configuration have been identified. Among the geometric variables, the gap between electrodes is the governing parameter of uniformity; it scales the magnitude of edge effect.     

梁压区边缘设置碳纤维板抗弯承载力试验研究

对2根受压区设置CFRP板的钢筋混凝土适筋梁进行静载四点弯曲试验,分别为在受压区设置一层CFRP板和二层CFRP板.实测轴向荷载-挠度关系曲线,分析加固梁的受压破坏形式、受压区设置CFRP板对适筋梁抗弯承载力、挠度以及应变的影响规律,同时进行1根普通钢筋混凝土适筋梁的静载试验,与受压区设置CFRP板的适筋梁进行比较,最后验证CFRP板加固混凝土构件应考虑CFRP板受压性能对构件承载力的提高作用,并推导出受拉面和受压面粘贴CFRP板加固的矩形截面受弯构件的正截面承载力计算公式.     

An investigation of the capacitance dispersion on the fractal carbon electrode with edge and basal orientations

Capacitance dispersion on the fractal carbon electrode with edge and basal orientations was investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and a.c.-impedance spectroscopy. For this purpose, four types of as-received pyrolytic graphite electrode, as-received, mechanically polished, and as-activated glassy carbon electrodes were prepared with different surface irregularities and amounts of edge orientations. The apparent self-similar fractal dimensions of the carbon electrodes were determined from the analyses of AFM images based upon triangulation method. The amounts of edge orientations on the surface of the carbon electrodes were qualitatively estimated from the XPS analysis of surface acidic functional groups that were preferably formed on the edge planes by the heat treatment of the carbon electrodes. The values of the constant phase element exponent α determined from the apparent self-similar fractal dimensions did not accord with those α determined from the measured impedance spectra. Instead, they were closely related to the amounts of the edge orientations. From the results, it is indicated that the contribution of surface inhomogeneity is much higher than the contribution of the surface irregularity to the capacitance dispersion on the carbon electrode.     

Experimental Study and Numerical Analysis of a CFRP Butt-Joint between the Pipes of Dissimilar Materials

A butt-joint was formed between two pipes of dissimilar materials, steel and aluminum, by winding a wetted roving of carbon fiber with epoxy at ±45° angle. On the curing of the epoxy, a tight carbon fiber reinforced polymer (CFRP) sleeve was formed, joining the ends of the pipes. The CFRP butt-joint was characterized for two kinds of loads: tensile and bending. Based on the joint strength performance, the specimens were categorized into two groups, thin and thick CFRP sleeved specimens. In the tensile testing, the thin sleeved specimen failed through the breakage of the CFRP sleeve at the joint plane because the axial stress developed in CFRP sleeve exceeded the ultimate strength of the CFRP. However, the thick sleeved specimens resisted the axial load in the sleeve and the weaker adherend, the aluminum pipe, slipped out of the CFRP sleeve. In the flexural testing, the thin CFRP sleeved specimens also failed by failure of the CFRP sleeve at the joint plane while the specimens of thick CFRP sleeve failed by the formation of a plastic hinge near the edge of the CFRP sleeve.     

KOH活化石墨毡阳极用于印刷电路板蚀刻液的电解再生

石墨毡电极的润湿性和电化学活性对印刷电路板蚀刻液电解再生装置的性能有重要影响。在900℃下,用KOH对石墨毡进行活化处理,并将KOH活化石墨毡作为电解池阳极对酸性蚀刻废液进行电解再生。用SEM、XPS表征和分析了活化前后石墨毡炭纤维的表面形貌和元素组成。通过循环伏安（CV）和电化学阻抗谱（EIS）分析了石墨毡电极的电化学性能。结果表明,KOH活化石墨毡炭纤维表面含氧量由原始石墨毡的2.60%（原子百分数,下同）增加到6.27%,润湿性得到改善。缺陷C数量增多,对Cu（I）电化学氧化活性提高。KOH活化石墨毡比表面积较原始石墨毡增加了约42倍。KOH活化石墨毡用于电解实验,阳极电势和槽电压较原始石墨毡分别降低0.10和0.05~0.06 V。