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• Flexural tensile strengths calculated with tensile and compressive differences are reduced by nearly 20 % when compared to those calculated without tensile and compressive differences. • A power function decay model of the tension–compression moduli of cement stabilized macadam was established in the four-point bending fatigue test. • The fatigue damage model of cement stabilized macadam was established and its accuracy was verified. Cement stabilized macadam (CSM) is a mixture created by combining cement as a binding material, water, and various particle sizes of minerals. The cement stabilized macadam material exhibits different moduli in tension and compression due to both its mechanical properties and the mechanical response in the asphalt pavement structure. To explore the strength, modulus and fatigue damage characteristics of CSM under different tensile and compressive modulus, this paper carried out the research. The calculation formulas for flexural tensile strength and tension–compression modulus were derived based on the difference in tension–compression modulus. A four-point bending strength test of CSM was carried out. Four-point bending fatigue tests with varying stress ratios were performed. It reveals deterioration laws of tension–compression modulus during fatigue process. The double logarithmic fatigue equation of CSM, as well as its nonlinear fatigue damage evolution equation, are established based on fatigue life results. The results of an analytical solution for fatigue life of rectangular section beams based on damage mechanics were obtained and compared to the results of four-point bending fatigue tests. The results reveal that the modulus of CSM differs in tension and compression. The calculated flexural tensile strength with the tension and compression difference is nearly 20 % lower than without the difference. The calculation approach that does not account for the difference in tension and compression overestimates the flexural tensile strength of CSM. The tension–compression moduli of CSM exhibit a power function decay law in the four-point bending fatigue processes. In the first stage, the dynamic modulus decays at a steady rate, accounting for 90 % of total fatigue life. The second stage in the life ratio of 0.9 occurs when the decay rate of the modulus rapidly increases and enters the stage of sharp decay. Based on the results of the four-point bending test, the modulus decay model was created. The decay parameter m has an exponential relationship with the stress ratio. The relative errors between the mean values of fatigue life tests and the predicted values of the analytical solutions range from 10.8 to 30.6 percent. The established fatigue damage equation for CSM can better reflect its fatigue damage evolution law. The research findings have great significance to solve the determination of pavement materials parameters based on the difference in tension and compression modulus. It also has a specific reference value for asphalt pavement design theory and calculation method when the varied modulus of tension and compression are considered. [ABSTRACT FROM AUTHOR]

Piezoelectric composites will cause different degrees of deformation when ambient temperature changes during transportation, storage and use, affecting the performance and reliability seriously. The deformation measurement of cylindrical piezoelectric composites based on fiber Bragg grating (FBG) measurement is presented in this paper. The deformation and electromechanical properties of cylindrical piezoelectric composites over a wide range of temperature, from 233 K to 373 K, are investigated in detail. The deformation of piezoelectric composites in different directions is calculated. Adding deformation information, the frequency constant and dielectric constant data are modified. The results show that, at 233 K, the relative change of curvature of the cylindrical composite material in the arc direction is 0.024% and the relative change of deformation in the width and thickness direction are 0.018% and 0.026%, respectively. When the environment's temperature is increased to 100℃, the relative change of curvature in the arc direction is 0.019% and the relative changes of deformation in the width and thickness direction are 0.019% and 0.008%, respectively. After adding the deformation information, the most evident changes of frequency constant and dielectric constant are between 303 K and 333 K, the rate of change (slope) of frequency constant and the dielectric constant are −1.82983 kHz·mm/K(decreasing) and 3.85591 kHz·mm/K(increasing), respectively. [ABSTRACT FROM AUTHOR]

Biomass-derived metal/carbon hybrid functional materials are considered to be highly promising electrocatalysts for oxygen reduction reactions (ORR). This is because of the desirable properties that they offer, including their complex microarchitectures，low costs，and feasibility of large scale production. In this work, we report a bottom-up synthesis of an economical, highly-active, and stable ORR electrocatalyst -- Fe/Cu-phenolic supramolecule decorated hierarchical porous biomass-derived N-self-doped carbon aerogel. With our method of thermal carbonization of bimetallic polyphenol networks functionalized collagen/cellulose nanocrystals (Col/CNCs), this material is shown to have a large number of storage sites and enhanced diffusion kinetics for optimal electrocatalytic oxygen reduction. Thanks to the rich active functional groups of Col/CNCs, along with the interfacial adhesion ability of plant polyphenols, we successfully synthesized a group of carbon aerogel composites loaded with metal nanoparticles. Benefiting from the fractal structure of the natural building blocks, the as-synthesized Fe x Cu y /C Col-CNCA presents a hierarchical porous structure, exquisite aerogel morphology and a heteroatom composition. With these advantages, it is demonstrated to have higher durability and better electrocatalytic ORR performance than the commercial 20% Pt/C. [Display omitted] • A versatile metal-phenolic networks (MPNs) coating strategy for fabricating porous N‑self-doped carbon aerogel. • Tannic acid with super interfacial adhesion for the stabilization and dispersion of the bimetal nanoparticles. • Novel electrocatalysts with exquisite aerogel morphology and heteroatom compositional advantages. • As-synthesized low-cost electrocatalysts manifest superior oxygen reduction performance and excellent durability. [ABSTRACT FROM AUTHOR]

Good conductive treatment of curved-surface piezoelectric composites could prevent failure of curved transducers, which are the core devices of many wideband and high-frequency sonar systems. A series of ratio between epoxy resin and curing agent were tested to investigate conductive treatments of curved-surface piezoelectric composites. The curved-surface piezoelectric composite was first prepared. The sample whose epoxy resin to and curing agent ratio was 100:150 showed the largest welding spot strength in many areas, but its homogeneity was not as good as samples with epoxy resin to curing agent ratio of 100:100 or 100:200. With increases in curing agent, the volume resistivities decreased, and the homogeneity became better. Unlabelled Image • Conductive treatment of curved surface piezoelectric composite was proposed. • The curved surface piezoelectric composite was prepared. • Application on curved surface piezoelectric composite material was discussed. [ABSTRACT FROM AUTHOR]