Hybrid glass fibre reinforced composites containing silica and cement microparticles based on a design of experiment

Hybrid Glass Fibre Reinforced Composites (HGRFCs) made with unidirectional glass fibres and silica or cement microparticles inclusions were investigated in order to improve their performance under flexural and impact loadings. Two full factorial designs were conducted to evaluate (i) the effect of the particle weight fraction on the compressive modulus of epoxy polymer (2¹3¹) and (ii) the effect of the number of layers and type of particle (3²) on the apparent density, flexural modulus and strength of HGFRCs. Composites with higher flexural properties were evaluated under impact loading via one-way analysis. TGA and FTIR analyses were used to verify the effect of ceramic particles within the polymeric phase. A microstructural analysis (SEM) was performed to verify the fracture mode and better assess the mechanical performance of HGFRCs.     

Stiffness evaluation of contacting surfaces by bulk and interface waves

This paper describes ultrasonic measurements of normal and tangential stiffnesses of the contacting interface between polished aluminum blocks subjected to nominal contact pressures up to about 3.8 MPa. These stiffnesses were evaluated by ultrasonic spectroscopy methods for the bulk (longitudinal and transverse) wave reflection coefficients and the anti-symmetric mode interface wave velocity. The measurements revealed the interfacial stiffnesses as functions of the frequency as well as the applied contact pressure. The ratio of the tangential and normal stiffnesses is discussed in the light of foregoing theoretical and experimental findings. Furthermore, possible explanations for the frequency dependence of the measured stiffnesses are reviewed, invoking the spatial inhomogeneity of the interfacial stiffness as well as its lossy nature.     

Mechanical properties of lateral transition metal dichalcogenide heterostructures

Transition metal dichalcogenide(TMD)monolayers attract great attention due to their specific structural,electronic and mechanical properties.The formation of their lateral heterostructures allows a new degree of flexibility in engineering electronic and optoelectronic dervices.However,the mechanical properties of the lateral heterostructures are rarely investigated.In this study,a comparative investigation on the mechanical characteristics of 1H,IT'and 1H/1T'heterostructure phases of different TMD monolayers including molybdenum disulfide(M0S₂)molybdenum diselenide(MoSe₂),Tungsten disulfide(WS₂),and Tungsten diselenide(WSe₂)was conducted by means of density functional theory(DFT)calculations.Our results indicate that the impact of the lateral heterostructures has a relatively weak mechanical strength for all the TMD monolayers.The significant correlation bet ween the mechanical properties of the TMD monolayers and their structural phases can be used to tune their stiffness of the materials.Our findings,therefore,suggest a novel strategy to manipulate the mechanical characteristics of TMDs by engineering their structural phases for their practical applications.     

Lateral magnetic stiffness under different parameters in a high-temperature superconductor levitation system

Magnetic stiffness determines the stability of a high-temperature superconductor(HTS) magnetic levitation system.The quantitative properties of the physical and geometrical parameters that affect the stiffness of HTS levitation systems should be identified for improving the stiffness by some effective methods. The magnetic stiffness is directly related to the first-order derivative of the magnetic force with respect to the corresponding displacement, which indicates that the effects of the parameters on the stiffness should be different from the relationships between the forces and the same parameters.In this paper, we study the influences of some physical and geometrical parameters, including the strength of the external magnetic field(B0) produced by a rectangular permanent magnet(PM), critical current density(Jc), the PM-to-HTS area ratio(α), and thickness ratio(β), on the lateral stiffness by using a numerical approach under zero-field cooling(ZFC)and field cooling(FC) conditions. In the first and second passes of the PM, the lateral stiffness at most of lateral positions essentially increases with B0 increasing and decreases with β increasing in ZFC and FC. The largest lateral stiffness at every lateral position is almost produced by the minimum value of Jc, which is obviously different from the lateral force–Jc relation. The α-dependent lateral stiffness changes with some parameters, which include the cooling conditions of the bulk HTS, lateral displacement, and movement history of the PM. These findings can provide some suggestions for improving the lateral stiffness of the HTS levitation system.     

Infinite Compressibility States in the Hierarchical Reference Theory of Fluids. II. Numerical Evidence

Continuing our investigation into the Hierarchical Reference Theory of fluids for thermodynamic states of infinite isothermal compressibility _T we now turn to the available numerical evidence to elucidate the character of the partial differential equation: Of the three scenarios identified previously, only the assumption of the equations turning stiff when building up the divergence of _T allows for a satisfactory interpretation of the data. In addition to the asymptotic regime where the arguments of part I directly apply, a similar mechanism is identified that gives rise to transient stiffness at intermediate cutoff for low enough temperature. Heuristic arguments point to a connection between the form of the Fourier transform of the perturbational part of the interaction potential and the cutoff where finite difference approximations of the differential equation cease to be applicable, and they highlight the rather special standing of the hard-core Yukawa potential as regards the severity of the computational difficulties.     

Infinite Compressibility States in the Hierarchical Reference Theory of Fluids. I. Analytical Considerations

In its customary formulation for one-component fluids, the Hierarchical Reference Theory yields a quasilinear partial differential equation (PDE) for an auxiliary quantity f that can be solved even arbitrarily close to the critical point, reproduces non-trivial scaling laws at the critical singularity, and directly locates the binodal without the need for a Maxwell construction. In the present contribution we present a systematic exploration of the possible types of behavior of the PDE\ for thermodynamic states of diverging isothermal compressibility _T as the renormalization group theoretical momentum cutoff approaches zero. By purely analytical means we identify three classes of asymptotic solutions compatible with infinite _T, characterized by uniform or slowly varying bounds on the curvature of f, by monotonicity of the build-up of diverging _T, and by stiffness of the PDE in part of its domain, respectively. These scenarios are analzyed and discussed with respect to their numerical properties. A seeming contradiction between two of these alternatives and an asymptotic solution derived earlier [Parola et al., Phys. Rev. E 48:3321 (1993)] is easily resolved.     

Characteristic Analysis of Bending Coupling Between Two Optical Waveguides

By means of the coupled mode theory and transfer matrix technique, a method is presented for analyzing the bending coupling between straight and bent rectangular waveguides, or between two bent rectangular waveguides. Calculations show that an effective coupling region exists around the central coupling point, in which the bending coupling appears, beyond which the bending coupling is very weak, and the propagation power in each waveguide becomes constant. When the bending radius becomes larger or the central coupling gap becomes smaller, this effective coupling region becomes wider, in which the coupling behavior becomes stronger.     

NQR investigations in crystalline 2,5-dichloroacetanilide

Two close NQR lines were observed in 2,5-dichloroacetanilide at room temperature at 34.606 MHz and 35.212 MHz as well as at liquid nitrogen temperature at 34.832 MHz and 35.791 MHz, using a self-quenched super-regenerative spectrometer. Analysis of the Zeeman effect on the two lines using a cylindrical single crystal reveals that the crystal belongs to either orthorhombic or monoclinic system. There are two crystallographically equivalent but physically non-equivalent directions for the principal field gradientZ axes making an angle of 77° for both resonance lines. The unit cell contains either two or a multiple of two molecules. There is an in-plane bending of the two C-Cl bonds by 1°. The ionic, single bond and double bond characters of C-C1 bonds for both chlorines are almost equal and are in the ratio 25:74:1.     

Recent advances in methods for numerical solution of O.D.E. initial value problems

This is a review paper which describes recent advances in numerical methods and computer codes for solving initial value problems of ordinary differential equations. Particular emphasis is placed upon stiff systems.     

Management of both toughness and stiffness of polypropylene nanocomposites using poly(5‐hexen‐1‐ol‐co‐propylene) and silica nanospheres

We developed novel polypropylene (PP)/silica nanocomposites using PP and silica nanospheres (SNSs) combined with poly(5‐hexen‐1‐ol‐co‐propylene) (PPOH), which is a functionalized PP containing hydroxyl groups that was assumed to play a role as not only an elastomer but also an interface modifier. Since the affinity between the PP matrix and silica filler was expected to be improved by blending with PPOH, its influence on the mechanical properties, structure, and toughness of the ternary composites was examined in detail to provide a better understanding of the role of the matrix‐filler affinity on the mechanical properties. The dispersity of the SNSs in the fabricated PP/PPOH/SNS nanocomposite was improved by increasing the hydroxyl group content of PPOH due to the enhanced affinity between PPOH and the SNSs. The SNSs in the composite with PPOH containing 6.4 mol% hydroxyl groups (PPOH6.4) were almost dispersed in the microscale domain, while the SNSs in the composite with 1.3 mol% hydroxy groups (PPOH1.3) were considerably aggregated. The toughness of the nanocomposite was noticeably improved by blending PPOH6.4 without a significant loss of stiffness. In contrast, the toughness was hardly improved using PPOH1.3. Therefore, both the fine dispersion of the SNSs and the excellent affinity between PPOH6.4 and the SNSs contributed to the good balance of toughness and stiffness of the PP/PPOH/SNS nanocomposite.