Smart Behavior of Carbon Fiber Reinforced Cement-based Composite

The electrical characteristics of cement-based material can be remarkably improved by the addition of short carbon fibers. Carbon fiber reinforced cement composite (CFRC) is an intrinsically smart material that can sense not only the stress and strain, but also the temperature. In this paper, variations of electrical resistivity with external applied load, and relation of thermoelectric force and temperature were investigated. Test results indicated that the electrical signal is related to the increase in the material volume resistivity during crack generation or propagation and the decrease in the resistivity during crack closure. Moreover, it was found that the fiber addition increased the linearity and reversibility of the Seebeck effect in the cement-based materials. The change of electrical characteristics reflects large amount of information of inner damage and temperature differential of composite, which can be used for stress-strain or thermal self-monitoring by embedding it in the concrete structures.

Martensitic transformation and magnetic properties of aged Ni-Fe-Ga-Ti shape memory alloy

This article reports the effect of ageing on the microstructure, martensitic transformation, magnetic properties, and mechanical properties of Ni51FelsGa27Ti4 shape memory alloy. There are five specimens of this alloy aged at 573 up to 973 K for 3 h per each. This range of ageing temperature greatly affects the microstructure of the alloy. As the ageing temperature increased from 573 up to 973 K, the microstructure of Ni51FelsGa27Ti4 alloy gradually changed from the entirely martensitic matrix at 573 K to the fully austenitic microstructure at 973 K. The volume fraction of precipi- tated Ni3Ti particles increased with the ageing temperature increasing from 573 to 773 K. Further increasing the ageing temperature to 973 K decreased the content of Ni3Ti in the microstructure. The martensitic transformation tempera- ture was decreased steadily by increasing the ageing temperature. The magnetization saturation, remnant magnetization, and coercivity increased with the ageing temperature increasing up to 773 K. A further increase in ageing temperature decreased these raagnetic properties. Moreover, the hardness values were gradually increased at first by increasing the ageing temperature to 773 K, and then dramatically decreased to the lowest value at 973 K.

THERMOMECHANICAL RESPONSE OF SMA FIBER COMPOSITES WITH NON-UNIFORM TEMPERATURE DISTRIBUTION

A micromechanics method based on the High-Order-Theory developed by Aboudi et al.is used to predict the thermomechanical response of composites reinforced by shape memory alloy (SMA) fibers,and the non-uniform thermal distribution in composite arising from the process of heating or cooling is considered.The numerical development based on this model was coded to predict the thermomechanical response of shape memory alloy fiber/elastomer matrix composite subjected to thermal cycle loading.When the composite is heated,two heating ways,thermal gradients and heat source by passing an electric current through the SMA fibers are imposed on the composite respectively.Upon cooling,the first thermal boundary condition and the second thermal boundary condition are subjected to the composite respectively.A series of stress distributions and temperature distributions for different instants are calculated to reveal the interaction between the SMA material and matrix.It is useful to analyze and design the SMA actuator driven by heat source or the surface temperature.

Properties and Application of Iron-based Shape Memory Alloy

The properties of FeMnSiCrNi shape memory alloy were investigated. The results show that the best shape memory effect of Fe14Mn6Si9Cr5Ni alloy is 85%. The transformation amount of the ε→γ transformation is not complete after heating the alloy to 1000 K, As and Af points drop with increased transformation enthalpy (ΔH γ→ε ) by thermal cycling and increased prestrain. The alloy shows also good creep and stress relaxation resistance. In addition, the alloy having a tensile force of 20 kN and a sealing pressure of 6 MPa can satisfy requirements for possible industrial application on pipe joints.

Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

Low-cost iron-based shape memory alloys（SMAs） show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion（HSHPT） process on the microstructural evolution of an Fe–Mn–Si–Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ε-martensite with an HCP crystal structure and γ-phase with an FCC structure.

Preparation of multi-walled carbon nanotube-reinforced TiNi matrix composites from elemental powders by spark plasma sintering

Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.

Research Status and Development Direction of Smart Clothing Materials

With the continuous development of technology and society, smart devices have filled people’s lives and become an indispensable part of people’s lives. At the same time, smart clothing has also been greatly developed. This article introduces several smart clothing materials, analyzes the current research status of smart clothing materials, and further discusses the applications of smart clothing materials in military, medical, intelligent decoration, and sports and leisure fields. Then the problems of smart clothing in safety, environmental protection, and industrial technology are analyzed, and the corresponding solutions to these problems are proposed, so as to provide reference and guidance for the future development of smart clothing in China. And the research shows that smart clothing will develop in the direction of fashion and diversification, function and comfort, safety and environmental protection, convenience and low cost in the future.

形状记忆合金增强水泥基复合材料及其构件研究进展

传统的水泥基材料适用性强、经济性高、用途广泛,但是容易开裂,难以恢复。通过热弹性马氏体相变及其逆相变,形状记忆合金拥有了独特的形状记忆效应、超弹性等卓越性能。因此,可以利用形状记忆合金增强水泥基材料及构件,克服传统水泥基材料抗裂性能差的缺陷,改善水泥基材料构件的开裂和变形自恢复能力。本文从形状记忆合金的材料特性与种类、形状记忆合金纤维增强水泥基复合材料及形状记忆合金筋材增强水泥基复合材料构件三个方面进行综合阐述,并指出现有研究中存在的不足,展望了形状记忆合金增强水泥基复合材料的发展前景。

柔性薄膜复合形状记忆合金弹簧驱动器

针对形状记忆合金(shape memory alloy,简称SMA)材料在使用过程中因其较低的响应频率而很难应用于高频率场所问题,在聚偏氟乙烯(polyvinylidene fluoride,简称PVDF)薄膜中引入锆酸铅钡(Pb_(0.8)Ba_(0.2)ZrO_(3),简称PBZ)纳米陶瓷纤维制备柔性薄膜,并与NiTi合金弹簧复合制得PBZ/PVDF@SMA复合驱动器,通过薄膜的电卡效应加热及冷却SMA丝,与传统电流加热及自然冷却方式进行了对比。结果表明,缩短了SMA丝循环周期,提高了其响应频率,有利于扩大SMA的适用场所。

形状记忆聚合物及其复合材料空间辐照环境效应研究进展

形状记忆聚合物及其复合材料具有密度低、可回复变形大、刺激方式可控、成本低等优点,可应用于空间可展开结构,但空间辐照环境对其在轨安全带来了严重的威胁。首先介绍了形状记忆聚合物及其复合材料的分类,接着总结了基于形状记忆聚合物的空间可展开结构应用现状,然后分析了高能电磁辐射、高能粒子辐射和原子氧等空间环境对形状记忆聚合物及其复合材料性能的影响,最后对形状记忆材料空间辐照环境效应的研究成果进行了总结并对未来发展方向进行了展望。

异形纤维及其制造技术进展

异形纤维是指横截面形状为非圆形的纤维,可弥补圆形纤维在抗扭强度、粗糙度、弹性、表观等性能方面的不足,并具有良好的光泽、染色、抗污、阻燃、隔热、隔音等性能,在纺织、复合材料、建筑、生物医学、汽车、航空航天、光学等领域得到了广泛应用。文中介绍了异形纤维的类型、特点、应用领域,总结了异形纤维的制造技术及其影响因素,分析了异形纤维横截面形态表征方法及对性能的影响。相关综述可为异形纤维的研究开发提供科学参考和技术借鉴。

Ni-Mn基磁性形状记忆合金弹热制冷效应的研究现状

弹热制冷不仅具有大而可逆的温度变化,而且其驱动方式更为简单,同时兼具环保、高效、节能的特点,平衡了成本、制冷量、效率以及可行性,有望成为替代传统蒸汽压缩冷却技术的候选之一。本文综述了Ni-Mn基磁性形状记忆合金弹性热效应的研究进展,从掺杂合金元素、热处理方法以及制备工艺等多个方面,总结了近年来对Ni-Mn基合金弹性热效应进行改进优化的研究成果。然而,目前Ni-Mn基合金弹热制冷材料的研究仍处于探索阶段,实现其实际应用还需进一步深入研究。未来的研究重点应集中在降低驱动能耗、提升疲劳寿命和循环稳定性、提高绝热温变以及优化传热效率等方面。

Improvement of impact resistance of plain-woven composite by embedding superelastic shape memory alloy wires

Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.

Improving interface adhesion in TiNi wire/shape memory epoxy composites using carbon nanotubes

In order to increase both the interfacial strength and interphase region strength between TiNi wires and shape memory epoxy,a novel interface structure including aminated CNTs was designed.The morphology shows that after electroplating and etching,continuous and homogeneous concave-convex layers form on the surface of astreated TiNi wires,meanwhile aminated CNTs were planted on the surface which could react with shape memory epoxy at the interface region.The interfacial shear strength increases first with the CNT content rising but then a dramatic drop happens,and the maximum is obtained at CNT content of 0.6 g·L^(-1),which is about twice the result of acid etching TiNi wires.

形状记忆合金研究进展与高熵形状记忆合金

形状记忆合金具有形状记忆效应、超弹性、良好的耐蚀性及力学性能等,是一种极具发展潜力和应用价值的功能材料,形状记忆合金自研发之初就受到了人们的广泛关注,目前已在诸多领域得到了广泛应用。系统总结了形状记忆合金的种类、制备方法、主要应用领域和最新的研究成果等,重点综述了目前研究的热点——高熵形状记忆合金的研究进展,并从合金成分、热机械处理、相结构3方面阐明了影响高熵形状记忆合金性能的因素,理清了阻碍形状记忆合金发展的主要因素,分析了高熵形状记忆合金的研究价值,并对形状记忆合金的未来发展方向进行了展望。

基体配比对VIHPS制备GO-CF/EP复合材料微观组织与形状记忆性能的影响

碳纤维混杂增强复合材料由于具有重量轻、可设计性强等诸多优点,广泛用于汽车、海洋、航空航天等行业.根据固化剂与环氧树脂的配比化学原理,计算出石墨烯-碳纤维混杂增强树脂基(GO-CF/EP)复合材料的最佳配比为1∶5,并采用真空浸渗热压成型工艺(VIHPS)制备1∶2~1∶7共六个配比的试样,结合形状记忆性能测试及微观形貌的观察,得到固化剂与环氧树脂实际最佳配比.实验结果表明,GO-CF/EP复合材料性能主要取决于体系中交联度的大小,交联度越大,复合材料的形状记忆性能越好,微观组织形貌也较理想.当基体配比为1∶5时,GO-CF/EP复合材料体系中交联度最大,微观形貌呈现均匀致密的状态,形状固定率最大,为95.90%;形状回复率最大,为95.40%;形状回复时间最短,为80.30 s;形状回复力最大,为9.48 N.当基体配比为1∶2或1∶7时,固化剂过量或不足,交联度较小,微观组织形貌中有大量的基体聚集区,其形状记忆性能下降,形状固定率及回复率也相应减小,分别为82.99%,81.66%,81.91%,78.75%;形状回复力分别只有5.20 N和5.50 N.

形状记忆聚合物复合材料及其在空间可展开结构中的应用

综述了形状记忆聚合物复合材料及其在空间可展开结构中的应用。形状记忆聚合物是一种智能主动变形的高分子材料,该材料在外界激励作用下能够产生较大的可回复变形,可应用于智能主动变形结构。首先简述了形状记忆聚合物的研究现状,然后分别介绍了颗粒、短纤维和连续纤维增强的形状记忆聚合物复合材料的研究现状,并重点评述了三种复合材料的电-热致驱动变形性能。此外,本文还介绍了纤维增强形状记忆复合材料在空间可展开结构上的应用,主要包括可展开铰链、可伸缩梁和可展开天线等。

形状记忆聚合物复合材料的研究进展

形状记忆聚合物复合材料已成为形状记忆材料的研究热点和重点,文中针对近年来形状记忆聚合物复合材料的最新研究进行了综述。分别对颗粒增强、纤维增强和颗粒纤维混合3类增强材料制备的形状记忆聚合物复合材料的结构与性能特点进行了分析和评述;着重阐述了形状记忆聚合物复合材料形状记忆效应的机理以及影响形状记忆行为的因素;分析了形状记忆聚合物复合材料研究中存在的问题,同时对形状记忆聚合物复合材料的应用前景进行了展望。

复合材料圆柱螺旋弹簧的制造与实验研究

对玻璃纤维复合材料圆柱螺旋弹簧的加工和弯曲力学性能进行了研究。通过大量探索性试验确定了复合材料弹簧的成型工艺流程 ,讨论了弹簧的加工工艺及结构参数对其弯曲回弹力、回复率及拉伸性能等的影响规律。研究结果表明 ,复合材料弹簧的弯曲力学性能与弹簧内径、纤维束的捻度、股数及直径等有直接关系 ,并受弯曲、回复时间的影响 。