基于碳纳米管改性0-3-1型水泥基压电复合材料诱导极化工艺的研究

采用碳纳米管对0-3-1型压电复合材料进行改性,研究了诱导极化电压(E1)、诱导电压方向、极化温度(T)、极化时间(t)、二次极化电压(E2)等相关因素对0-3-1型水泥基压电复合材料压电性能的影响,确定了0-3-1型水泥基压电复合材料最优的极化工艺和制备过程。结果表明,碳纳米管改性0-3-1型水泥基压电复合材料的最优诱导电场方向为与1型陶瓷柱夹角为30°方向,合理诱导电压为600 V/cm,合理二次极化电压为3 kV/mm,合理极化温度为100℃,合理极化时间为30 min。     

路面用环氧基压电复合材料制备及性能

为了制备适合于路面用的压电复合材料,以锆钛酸铅(PZT)为压电相,以环氧树脂为基体,采用压制成型法制备0-3型PZT/环氧树脂压电复合材料.分析了PZT的体积分数、制备工艺和极化条件对复合材料压电应变常数的影响,测试了环氧基压电复合材料的介电性能,并完成了动态荷载作用下压电响应的测试.研究结果表明:PZT的体积分数为75％时压电复合材料电性能最好;最佳的极化条件为极化电压2.25kV/mm、极化时间15min和极化温度90℃,但成型压力和成型时间对环氧基压电复合材料影响很小.在PZT体积掺量为75％,最佳成型和极化条件下,压电复合材料的介电常数及压电应变常数分别为210.53和64 pC/N;并在该复合压电材料施加正弦稳幅荷载(频率:10Hz,均值:-600N,幅值:400N),其可稳态输出8.1V电压,其储存的能量为304.2uJ.     

碳纳米管水泥基复合材料机敏性能研究

为了研究碳纳米管水泥基复合材料在循环荷载下的机敏性能,将多壁碳纳米管作为增强相,采用非共价表面活性剂吸附分散技术,使多壁碳纳米管尽可能均匀地分散在水泥净浆中制备碳纳米管水泥基复合材料,分析了碳纳米管掺量、试件尺寸、循环荷载等因素对其机敏性能的影响。试验结果表明:在循环荷载作用下,纳米管水泥基复合材料的电阻率ρ随着加卸载出现可逆性循环变化,表现出了良好的机敏性能,多壁碳纳米管的较佳掺量为0.2%,且尺寸较小的试件表现出的机敏性更优。因此,碳纳米管复合材料可发展成为一种新型的传感器用于结构的健康监测。     

椰壳纤维增强水泥基复合材料微观组织研究

将椰壳纤维加入到水泥砂浆基体中,制备椰壳纤维增强轻质水泥基复合材料,对材料内部纤维结构、纤维成分、纤维与基体界面、断裂机理进行分析,结果表明:椰壳纤维与水泥基体具有良好的物理相容性和化学相容性。     

路面用PZT/沥青压电复合材料的制备及性能

以锆钛酸铅PZT 5H为压电相,沥青为基体,采用热压成型法制备0 3型PZT/沥青压电复合材料.分析了此复合材料的制备工艺、极化条件及PZT的体积分数对压电应变常数d33的影响,测试了其介电性能,并完成了动态荷载作用下压电响应的测试.结果表明：优化的制备工艺为成型压应力10MPa,成型时间3min;最佳的极化条件是极化电场强度为3kV/mm,极化时间为10min,极化温度为50℃;PZT的最佳体积分数为75%;沥青基压电复合材料的相对介电常数εr及压电应变常数d33分别为3295和537pC/N,荷载响应稳态输出电压为72V,其储存的能量为2592μJ.     

碳纳米管水泥基材料耐久性理论探讨

碳纳米管是近几年国内外纳米材料界研究的热点。在建设工程中,水泥基材料的耐久性问题日益突出。本文在介绍碳纳米管的结构性能和水泥基材料的耐久性问题的基础上,分析了多壁碳纳米管改善水泥基材料耐久性的可能性,得出拟解决的关键问题是多壁碳纳米管在基体中的均匀分散和其与基体的相容性以及水泥基复合材料的耐久特性和机理,为工程应用奠定基础。     

损伤自诊断机敏混凝土材料研究

具有机敏特性的水泥基复合材料日渐成为研究热点。本文研究了掺有碳纤维的混凝土材料在单轴受压和三点弯曲负荷下的电阻相对变化与材料内部损伤间关系，为开发具有自诊断功能的混凝土材料提供了材料基础。     

水泥基智能材料构筑及机敏性能研究

通过掺入钢纤维和超导纳米炭黑,并调节其掺量,采取规范的制备流程,实验分析制备高性能混凝土的新拌浆体性能、机械性能、机敏性能,力求使制备的混凝土具备高强、自诊断、易检测等特性.结果表明,当混凝土水胶比为0.18、钢纤维掺量2％、纳米炭黑掺量0.5％时,制备的水泥基材料达到预定要求.因此,钢纤维—纳米炭黑复合材料在新型智能...     

碳纤维混凝土的交流阻抗性能研究

随着水泥基材料的发展,人们对水泥基材料提出了更新的要求,其中水泥基导电复合材料的研究引起了广泛的兴趣.制备水泥基导电复合材料的方法是在水泥基材料中掺入各种导电组分,目前较常用的是掺人碳纤维,它可以大幅度提高水泥基复合材料电导率.本文通过对碳纤维混凝土的交流阻抗特性分析,研究了其内部微结构与电导性能的关系.     

水灰比对椰壳纤维增强水泥基复合材料的性能影响

制备水灰比不同的两组椰壳纤维增强水泥基复合材料,分析其综合性能。结果表明:加入椰壳纤维后,椰壳纤维水泥基复合材料密度明显降低、吸湿性和吸水性增大,抗压强度下降幅度较大而抗弯强度下降不明显。另外,水灰比的降低能够提高材料的密度,使得材料的抗压和抗弯强度都有较大幅度的提高。指出该材料在轻质填充材料上具有一定的开发和研究价值。     

水泥基导电复合材料的电热特性

测试了石墨导电水泥和碳纤维－石墨导电水泥的相关性能，发现它具有表面温度低，抗过电压和过电流能力强，性能稳定，耐久性好等优点，适合用作暖房地面等电热器材料。     

Preparation and characteristics of n-nonadecane/cement composites as thermal energy storage materials in buildings

n-Nonadecane/cement composites as thermal energy storage materials (TESM) were prepared by absorbing n-nonadecane in porous network of cement. In composite materials, n-nonadecane was used as the phase change material (PCM) for thermal energy storage, and cement acted as the supporting material. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine the FT-IR spectra, the crystalloid phase and microstructure of n-nonadecane/cement composites, respectively. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that n-nonadecane was well dispersed in the porous network of cement. The DSC results indicated that the n-nonadecane/cement composite material has the melting latent heat of 69.12 kJ/kg with melting temperature of 31.86 °C, and solidifying latent heat of 64.07 kJ/kg with solidifying temperature of 31.82 °C.     

采用压电智能材料的土木工程结构控制研究进展

本文首先简要介绍了压电材料和压电陶瓷驱动器的基本特性;其次,回顾了运用压电材料进行土木结构振动控制的发展历程,详细介绍了应用压电材料的智能驱动器和耗能器;最后,对压电材料在土木结构振动控制中研究与应用前景进行了展望。     

压电智能混凝土梁主动控制试验研究与有限元分析

基于8根压电智能混凝土梁的主动控制试验,较为系统地研究压电智能混凝土梁在静力荷载和压电驱动器产生的驱动力作用下的变形恢复能力、应变恢复特性和裂缝闭合特征,重点分析配筋率、跨高比和驱动器埋设位置等因素的影响。试验结果表明,通过对压电智能混凝土梁施加驱动力,可以有效地实现智能混凝土梁的应变、变形和裂缝的主动控制,其中应变恢复率达到30%左右,变形恢复百分比在21%-42%之间,裂缝宽度闭合程度大致在12%-15%之间。另外,基于非线性有限元原理,编制压电智能混凝土梁的分析程序,实现压电智能混凝土梁主动控制的全过程分析。     

钢纤维水泥基复合材料断裂的K R曲线研究

基于Wallin阻力曲线模型,结合纤维增强复合材料断裂理论,提出了钢纤维水泥基复合材料的K-R曲线模型.通过定向与乱向两种纤维分布形式以及不同尺寸的预制缺口三点弯曲梁断裂试验,验证了K-R曲线模型的合理性与适用性.结果表明:K-R曲线模型能够有效描述不同钢纤维分布形式下水泥基复合材料的断裂过程,且理论预测的峰值荷载与试验结果偏差较小.该模型可为钢纤维水泥基复合材料的断裂参数尺寸效应研究提供新方法.     

The study of pore structure and its influence on material properties of cement-based piezoelectric ceramic composites

In order to investigate the pore structure and its influence on the material properties of cement-based piezoelectric ceramic composites, specimens with different ceramic/cement ratio of composite are prepared. The pore structure of composite is obtained by using mercury intrusion porosimetry (MIP). The variety of pore structure is attributed to the chemical reaction at the surface of PZT particles and cement grains, which is different with that of cement paste. And the porosity of composite reduces with the increasing of ceramic/cement ratio. Moreover, the influence of pore structure on the mechanical and dielectric properties of composite are discussed in detail. A monotonic decreasing of material properties of composite with total intruded pore volume is found.     

Smart behaviour of layered plates through the use of auxetic materials

The development of smart structures, aimed at optimizing the response of engineering systems, is a modern and very promising field. Such advanced structural element can be obtained, in some cases, by using the so-called auxetic materials, i.e. materials exhibiting negative Poisson׳s ratio. In the present paper a brief introduction on auxetic materials and on their use and potentiality is presented. In particular their application to obtain smart layered plates is discussed; it is shown as these materials allow, in certain conditions, to get a desired stiffness and a nearly linear behaviour (even under large displacement conditions) of bended plates, without changing the plate׳s geometry and materials. Such potentialities are presented and discussed based on numerical analyses, and a mechanical interpretation of the observed structural behaviour is proposed.     

Numerical simulation model of vibration responses of rectangular plates embedded with piezoelectric actuators

A numerical simulation model for random large amplitude vibration control of composite plate using piezoelectric material is presented. The H_∞ control design is employed to suppress the large amplitude vibrations of composites plates under random loading. The numerical simulation model is developed and based on the finite element method. The finite element governing equation includes fully coupled structural and electrical nodal degrees of freedom, and consider the von Karman large amplitude vibration. The modal reduction method using the structural modes is adopted to reduce the finite element equations into a set of modal equations with fewer degrees of freedom. The modal equations are then employed for controller design and time domain simulation. In the simulations without control, the value of the linear mode to the nonlinear deflection is quantified; and the minimum number of linear modes needed for accurate model is obtained. In the simulations with control, it is shown that the truncated modes, which are neglected in the control design, deteriorate the controller performance. Generally, the vibration reduction level is not monotonically increasing with the size of the piezoelectric actuator. The optimal piezoelectric actuator size depends on the excitation level. For higher excitation level, optimal actuator size is larger. The H_∞ controller based on the linear finite element formulation gives better vibration reduction for small amplitude vibration, but it still gives reasonable performance for large amplitude vibration provided that the piezoelectric actuator is big and powerful enough.     

压电材料主元杆件的基本力学性能

提出了一种实用的新型含压电堆材料的主元杆件,阐述了其应用于钢结构稳定控制的基本工作机理,讨论了该主元杆件在不考虑机电耦合及考虑机电耦合时的极限承载力的改变,同时运用有限元法,讨论了压电主元杆件中含压电堆的长度对其静力稳定性的影响,并进行了数值计算.结果表明:考虑机电耦合能够显著提高主元杆件的极限承载力;主元杆件所含压电堆的长度对静力稳定性的影响并非线性提高,而是必须在特定的刚度优化时才能进行有效地控制.     

掺粉煤灰的MDF水泥材料结构与性能研究

研究了用粉煤灰部分替代水泥而制备的HAC/PVA基MDF材料的强度、水敏性与结构,试验结果表明,粉煤灰细粉的掺入虽然改善了MDF水泥材料的孔结构和水敏性,但却明显降低其力学性能,用硅烷偶联剂对粉煤灰和水泥进行表面改性,则能显著提高粉煤灰MDF水泥材料的抗折强度,进一步改善其水敏性。