Tuning the mechanical properties of glass fiber-reinforced bismaleimide–triazine resin composites by constructing a flexible bridge at the interface

Abstract

We demonstrate a new method that can simultaneously improve the strength and toughness of the glass fiber-reinforced bismaleimide–triazine (BT) resin composites by using polyethylene glycol (PEG) to construct a flexible bridge at the interface. The mechanical properties, including the elongation, ultimate tensile stress, Young’s modulus, toughness and dynamical mechanical properties were studied as a function of the length of PEG molecular chain. It was found that the PEG molecule acts as a bridge to link BT resin and glass fiber through covalent and non-covalent bondings, respectively, resulting in improved interfacial bonding. The incorporation of PEG produces an increase in elongation, ultimate tensile stress and toughness. The Young’s modulus and T_g were slightly reduced when the length of the PEG molecular chain was high. The elongation of the PEG-modified glass fiber-reinforced composites containing 5 wt% PEG-8000 increased by 67.1%, the ultimate tensile stress by 17.9% and the toughness by 78.2% compared to the unmodified one. This approach provides an efficient way to develop substrate material with improved strength and toughness for integrated circuit packaging applications.     

Fabrication and mechanical properties of aramid/nylon plain knitted composites

The presence of fibre/matrix interfaces strongly influences the overall mechanical properties of composites. In order to produce fully recyclable fiber reinforced composites with improved adhesion properties, polyethylene and polypropylene materials were previously used as single-polymer composite materials. In this paper, another breed of single-polymer composite material has been defined as the ‘one-unity’ composite. Polyamide materials were chosen and combined with aramid fibre in an attempt to achieve better interfacial bonding. Weft-knitting technique was used to produce textile reinforcements for aramid/nylon composite processing. Aramid/epoxy knitted composites were also fabricated to compare them with aramid/nylon thermoplastic composites. Mechanical properties of aramid/nylon and aramid/epoxy composites and their relationships to the fibre/matrix interfacial adhesion and interactions have been investigated. With the increase in processing time, tensile modulus and strength of aramid/nylon composites have increased and decreased, respectively. Furthermore, scanning electron microscopic observations clearly indicated that longer molding time has resulted in stronger adhesion property between fiber and matrix. Aramid/nylon knitted composites have revealed comparable strength property in the course direction, albeit they have inferior tensile strength in the wale direction when compared to that in aramid/epoxy composites. In aramid/nylon knitted composites, while tensile modulus exhibited an increasing trend, there were clear drops in tensile strengths with longer molding time. This indicates that there could be an optimum molding condition at which maximum tensile properties can be obtained. Aramid/nylon knitted composites exhibited relatively better interfacial bonding properties than Aramid/epoxy composites, which suffered fibre/matrix debonding.     

Influence of interface microstructure on the mechanical properties of Ti/Ni multi-layered composites

The research was performed to determine the influence of microstructural evolution at interfaces on the subsequent uniaxial tensile properties of Ti/Ni multi-layered composites. The microstructure and chemical composition of the interfaces were examined. The fracture feature of the tensile samples was studied. At longer annealing time, the diffusion regions between Ti and Ni elements from a single side changed to two sides and became thicker. The tensile strength of the annealed composites decreased initially, and then was slightly increased after 60?h. The elongation increased significantly relative to the original rolled samples. Fractography revealed brittle fracture areas produced in the Ti/Ni interfaces. The failure mode in the annealed Ti/Ni composites was a typical ductile mixed brittle fracture.     

Effect of strain rate on the mechanical properties of composites with a weak fibre/matrix interface

Modelling studies have indicated a strong effect of the rate of deformation on the tensile strength of composites with a weak fibre/matrix interface. At high rates, the mode of deformation changes from a fibre pull-out to a fibre breaking mechanism typical of good adhesion composites. As a result, the mechanical properties become independent of those of the fibre/matrix interface. The model predictions are of great importance because they allow a straightforward identification of composites with poor fibre-matrix adhesion.     

The interface,microstructure and mechanical properties of Cf/LAS glass-ceramic composites

Carbon fibre (C_f)-reinforced lithium aluminium silicate (LAS) glass-ceramic matrix composites were prepared by using LAS ultrafine powders and LAS sol as starting materials and binder, respectively. The effects of fibre content, hot-pressing temperature and pressure on the mechanical properties of the composites were studied. By means of SEM and theoretical calculation, the effects of thermal mismatching between fibre and matrix, and the microstructure on the mechanical properties of the composites were analysed and discussed. The flexural strength and fracture toughness of C_f/LAS glass-ceramic matrix composite prepared were 740 MPa and 19.5 MPa m^1/2, respectively. The wettability of carbon fibre with matrix was also investigated.     

Preparation of properties of SWNT/graphene oxide type flexible transparent conductive films

Single walled carbon nanotube (SWNT)/graphene oxide (GO) hybrid films were prepared by a facile bar coating method on a polyethylene terephthalate substrate using a mixed solution of SWCNTs and GO. An acryl type polymer was employed as a dispersion agent to obtain SWCNT and GO suspension in ethyl alcohol. The SWCNT/GO hybrid films were highly transparent and electrically conductive, showing 80% transmittance and 1.8 x 10(3) ohm/sq surface resistance. The surface resistance of the SWCNT/GO film could be further improved to 750 ohm/sq by hydrazine vapor reduction.     

Influence of microstructure of fibre/matrix interface on mechanical properties of Al/SiC composites

Abstract

The relationship between microstructure and mechanical properties of composites of squeeze cast Al–Cu and Al–Cu–Mg reinforced with 25 vol.-%SiC whiskers was investigated. Tensile test results were compared with values calculated using a modified rule of mixtures (ROM). The results were found to be in good agreement for the Al–Cu matrix composite, whereas a relatively large discrepancy was observed for the Al–Cu–Mg matrix composite. It was concluded from microstructural observations that this difference resulted from a reduction of the whisker strength due to more pronounced decoration of the interfaces by oxides and spinels. For the Al–Cu–Mg composite, the effect of interfacial phases on the composite strength must betaken into account when the modified ROM is applied.

MST/1242     

碳纤维-Ni/尼龙66复合材料的制备与性能表征

为制备低电阻率的尼龙66基复合材料,以碳纤维和镍粉(Ni)填充尼龙66制备碳纤维-Ni/尼龙66高导电复合材料。研究填料表面改性和含量对碳纤维-Ni/尼龙66复合材料导电性能和力学性能的影响。结果表明:KH550改性碳纤维和Ni有助于降低碳纤维-Ni/尼龙66复合材料的电阻率。碳纤维-Ni/尼龙66复合材料的电阻率随着碳纤维和Ni含量的增加而减小,且碳纤维和Ni填充尼龙66的导电逾渗阈值均为20wt%,此时制备的碳纤维-Ni/尼龙66复合材料的电阻率为455Ω·cm,熔融温度为202.2℃。碳纤维-Ni/尼龙66复合材料的弯曲强度和拉伸强度随着碳纤维或Ni含量的增加而先增大后减小。当Ni含量为20wt%时,碳纤维-Ni/尼龙66复合材料的弯曲强度和拉伸强度在碳纤维含量分别为20wt%和10wt%时达到最大值,分别为98MPa和70 MPa;当碳纤维含量为20wt%时,碳纤维-Ni/尼龙66复合材料的弯曲强度和拉伸强度则在Ni含量为30wt%和20wt%时达到最大值,分别为120 MPa和67 MPa。     

乙烯-乙烯醇共聚物/尼龙6复合材料的加工流变性能

采用熔融共混法制备了乙烯-乙烯醇共聚物/尼龙6(EVOH/PA6)复合材料,用高级毛细管流变仪和旋转流变仪研究了复合材料的加工流变特性.通过幂律模型对EVOH/PA6复合材料的黏度与剪切速率(?γ)的关系进行了拟合,并用Arrhenius方程描述了复合材料黏度与温度的关系.结果表明,EVOH/PA6复合材料为假塑性流体,复合材料的表观黏度(ηa)和非牛顿常数(n)随着EVOH添加量的增加而增大.在角频率(ω)扫描范围内,EVOH的加入提高了EVOH/PA6复合材料的储能模量(G')、损耗模量(G″)和复数黏度|η*|.用Han曲线、Cole-Cole曲线和扫描电子显微镜(SEM)等方法研究发现,EVOH和PA6之间具有较好的相容性.另外,EVOH/PA6复合材料在EVOH的添加量达到15％(质量分数)时形成了微观相分离结构.     

The mechanical properties and thermal conductivity of carbon/carbon composites with the fiber/matrix interface modified by silicon carbide nanofibers

For modification, silicon carbide nanofibers (SiCNFs) are uniformly dispersed on the fiber surface of the unidirectional carbon preform. The modified unidirectional carbon preform was then densified to obtain SiCNF–C/C composites by chemical vapor deposition (CVD). The microstructure of SiCNF–C/C composites was investigated. The mechanical properties and thermal conductivity of the modified composites were analyzed as well. Results show that PyC preferentially deposits on the surface of SiCNFs with high degree of order. The interface between carbon fibers and matrix has high texture, resulting in a good bonding between them. The mechanical properties of C/C composites are adjusted. After modification, the fracture mode is changed and the flexural strength is enhanced, especially in vertical direction. The thermal conductivity of modified composites is also enhanced in both vertical and parallel directions.     

Mass-production of flexible and transparent Te-Au nylon SERS substrate with excellent mechanical stability

Nano Research - In the past two decades, the field of surface-enhanced Raman scattering (SERS) has flourished and many rational strategies have been reported for the successful construction of SERS...     

粉末冶金法炭纤维/Mg复合材料的界面对其力学性能的影响

采用表面化学镀镍前后的短炭纤维(Cf)做为增强体,纯镁粉为基体金属,通过粉末冶金法和热挤压制备镁基复合材料.采用SEM-EDS、TEM、XRD和拉伸等测试手段表征短炭纤维增强镁基复合材料的微观形貌、元素组成、物相组成及其力学性能.结果表明:炭纤维在复合材料中分布均匀且沿挤压方向定向排列;采用经过表面化学镀镍处理的短炭纤维与金属镁复合后界面结合状态优良,Mg2Ni物相的存在表明润湿性的改善是通过金属镁与涂层发生反应而实现;对比屈服强度测试值和理论计算值的大小,表明涂层炭纤维增强镁基复合材料的增强机理主要是界面载荷传递效应.     

Hot-pressed hydroxylapatite/monoclinic zirconia composites with improved mechanical properties

Composites of hydroxylapatite (HA) and monoclinic zirconia were hot-pressed at 1100 °C and 1200 °C under vacuum to study the phase transformations and the mechanical properties. X-ray diffraction results showed a higher phase transformation from monoclinic-ZrO₂ to tetragonal-ZrO₂ when the sintering temperature increased from 1100 °C to 1200 °C. HA decomposed faster when the amount of ZrO₂ in the composites increased. Moreover, small amount of α-TCP and CaZrO₃ was observed in the composites hot-pressed at 1200 °C. Hot-pressing at 1100 °C resulted in better mechanical properties than the hot-pressing at 1200 °C because of less reaction between HA and zirconia at 1100 °C. 40 wt% monoclinic zirconia and HA composite hot-pressed at 1100 °C resulted in promising mechanical properties which are 6.5 GPa of Vickers μ-hardness, 2.23 MPa√m of fracture toughness, and 66 MPa of diametral strength.     

Mechanical properties of E-glass fibre reinforced nylon 6/6 resin composites

The tensile strength, tensile modulus, compressive strength, interlaminar shear strength and residual tensile strength of E-glass fibre reinforced nylon 6/6 resin composite with the variation of fibre volume fraction are characterized. The results are in line with the required limits of theoretical values.     

SiCP/Al复合材料的拉伸性能

对高体积分数碳化硅颗粒增强铝基(SiC_P/Al)复合材料的拉伸强度进行了试验研究。发现在较高应力水平下经过2次卸载的试件与未做卸载的试件相比,拉伸强度变化很小,说明加载-卸载过程对材料的拉伸强度影响不大。在试验研究的基础上,使用ANSYS软件建立了有限元模型,对SiC_P/Al复合材料的拉伸特性进行了仿真模拟。研究结果表明,低体积分数SiC_P/Al复合材料的力学性能更接近塑性材料;而高体积分数SiC_P/Al复合材料的力学性能则接近于脆性材料。拉伸强度模拟计算误差非常小,基体破坏是导致高体积分数SiC_P/Al复合材料破坏的主要因素。     

Thermoelastic properties of fiber composites with imperfect interface

Imperfect interface conditions are defined in terms of linear relations between interface tractions and displacement jumps. All of the thermoelastic properties of unidirectional fiber composites with such interface conditions are evaluated on the basis of the generalized self consistent scheme (GSCS) model. Results for elastic interphase are obtained as a special case by evaluation of interface parameters in terms of interphase characteristics. Numerical evaluation has shown that imperfect interface may have a significant effect on transverse thermal expansion coefficient, transverse shear and Young's moduli and axial shear modulus, a moderate effect on axial Poisson's ratio, small effect on axial thermal expansion coefficient and an insignificant effect on axial Young's modulus.     

尼龙6/橡胶/天然粘土纳米复合材料的制备及其力学性能

采用一种新型的超细全硫化粉末橡胶/蒙脱土复合粉末(UFPRM),可以制备出剥离型的尼龙6/橡胶/天然粘土(尼龙6/UFPRM)纳米复合材料,所用的橡胶是一种具有特殊结构的超细全硫化粉末橡胶(UFPR).微观分析表明,橡胶粒子在尼龙6基体中分散良好,同时天然粘土在橡胶粒子之间的基体中剥离.在一定份数下,复合粉末可以同时提高尼龙6的韧性、刚性及耐热性;随着复合粉末含量的增加,材料的冲击强度进一步增加.而且,复合粉末对高分子量尼龙6的增强、增韧效果好于低分子量尼龙6.进一步研究发现,在适当的剪切速率下,尼龙6/橡胶/天然粘土纳米复合材料可以获得较好的综合力学性能.     

Effects of interface characteristics on mechanical properties of carbon nanotube reinforced polymer composites

Abstract

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable candidates for use as reinforcements in composite materials. To take full advantage of their exceptional properties, load sharing mechanisms needs to be understood in the composite materials. Load transfer in composites is achieved through the fibre/matrix interface. In the present paper, finite element method is used to investigate the effects of interface behaviour on carbon nanotube based composite mechanical properties. The effective nanocomposite mechanical properties are evaluated using a three-dimensional nanoscale representative volume element (RVE). In this RVE approach, a single nanotube and the surrounding polymer matrix are modelled. Two cases of perfect bonding and an elastic interface are considered. In addition, the rule of mixtures relations is used to validate the results of numerical models. The results indicate that mechanical properties of nanocomposite materials are significantly influenced by the interface strength.