An investigation on failure behavior of semi-flexible composite mixture at different temperatures

Semi-flexible composite mixture(SFCM)is a kind of pavement material formed by pouring cement-based grout material into a porous asphalt mixture with air voids from 20%to 30%.SFCM is widely used for its outstanding anti-rutting performance.Its mechanical performance is complicated due to its heterogeneity and interlocking structure.According to the present study,asphalt deforms at different temperatures,whereas cement-based grout has no similar characteristics.Rare research focuses on the temperature-based performance of SFCM.Therefore,the study was on the thermal performance of SFCM by seven open-graded asphalt mixture skeletons with different porosities and two types of grouts with early strength(ES)and high strength(HS).The test temperatures ranged from 10℃to 60℃.The mechanical investigation was performed using the semi-circular-bending(SCB)and beam bending tests.The strain sensor was used for analyzing the thermal performance of SFCM.The results show that the temperature significantly affected the SFCM's performance.The porosity was selected for three sections based on the trend of fracture energy(Gf)curves at 25℃.The turning points were the porosity values of 20%and 26%.The initiation slope during elastic deformation increases with the porosity increase.This trend was more evident at intermediate temperature.The shrink strain of SFCM was lower than that of the usual asphalt mixture(AC).The thermal stress of the SFCM filled with HS(HS-SFCM)was higher than that of the SFCM filled with ES(ES-SFCM)at 10℃.Moreover,the thermal failure characteristics of SFCM were influenced by porosity.

Semi-flex印制板制作工艺研究

使用半固化片(PP)开窗法制作Semi-flex印制电路板时,半固化片开窗的尺寸及品质直接影响压合时树脂向Semi-flex印制板挠性区域的流动情况,进而影响其挠曲性能。本文使用开窗法制作挠性层为L5/L6层的10层Semi-flex印制板,研究了铣刀转速、叠合张数等加工参数对半固化片开窗品质的影响,以及半固化片开窗放大尺寸与压合时刚挠结合处PP溢胶长度的关系。为了验证产品其可靠性,对其进行了漂锡测试、回流焊测试和冷热冲击测试。

Mechanical Behavior and Failure Mechanism of Recycled Semi-flexible Pavement Material

The mechanical behavior and failure mechanism of recycled semi-flexible pavement material were investigated by different scales method. The macroscopic mechanical behavior of samples was studied by static and dynamic splitting tensile tests on mechanics testing system(MTS). The mechanical analysis in micro scale was carried out by material image analysis method and finite element analysis system. The strains of recycled semi-flexible pavement material on samples surface and in each phase materials were obtained. The test results reveal that the performance of recovered asphalt binder was the major determinant on the structural stability of recycled semi-flexible pavement material. The asphalt binder with high viscoelasticity could delay the initial cracking time and reduce the residual strain under cyclic loading conditions. The failure possibility order of each phase in recycled semi-flexible pavement material was asphalt binder, reclaimed aggregate, cement paste and virgin aggregate.

Miscibility of Semi-flexible Thermotropic Liquid Crystalline Copolyesteramide with Polyamide 66

Liquid crystalline polymer-polyamide 66 (LCP/PA66) blends were compounded by using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30% (molar fraction ) of p-amino benzoic acid (ABA ) and 70% (molar fraction) of poly (ethylene terephthalate) (PET). The LCP/PA66 blends were investigated in terms of the thermal and dynamic mechanical properties. It was found that PA66 and LCP components of the blends are miscible in the molten state, but are partially miscible in the solid state. The inclusion of the semi-flexible LCP into PA66 retards the crystallization rate of PA66. Furthermore, the melting temperature and the degree of crystallinity of PA66 are reduced considerably due to the LCP addition.

Simulation of the Critical Adsorption of Semi-Flexible Polymers

The critical adsorption of semi-flexible pol.ymer chains on attractive surfaces is studied using Monte Carlo simulations.The results reveal that the critical adsorption point of a free polymer chain is the same as that of an end-grafted one.For the end-grafted polymer,we find that the finite-size scaling relation and the maximum fluctuation of adsorbed monomers are equivalent in estimating the critical adsorption point.The effect of chain stiffness on the critical adsorption is also investigated.The surface attraction strength for the critical adsorption of semi-flexible polymer chain decreases exponentially with an increase in the chain stiffness;In other words,lower adsorption energy is needed to adsorb a stiffer polymer chain.The result is explained from the viewpoint of the free energy profile for the adsorption.

Study on Air-Purifying Performance of Semi-Flexible Asphalt Samples Coated with Titanium Dioxide Using Different Methods

Titanium dioxide(TiO_(2))was recently employed to apply onto road surfaces to degrade the harmful compounds from vehicle emissions.However,it remains a challenging task to find a highly compatible pavement type for TiO_(2)application to achieve durable and efficient air-purifying performance.This study proposed to coat TiO_(2)particles onto semi-flexible pavement surface and tried to investigate an optimum coating method.Three coating methods,including direct mixing TiO_(2)(MT)with asphalt mixture,spraying dry TiO_(2)(ST)coating and watersolution-based TiO_(2)(WT)coating on semi-flexible pavement surface.To achieve this objective,semi-flexible samples were prepared to evaluate and compare the performances of three coating methods by employing resistance to wearing,NO removal efficiency tests and residual texture depth tests.It was found that the ST method not only provided better NO degrading efficiency but also improved the resistance to wearing than the other two methods.

The Influential Factors of Semi-Flexible Pavement Cracking Performance

The cracking performance of semi-flexible pavement(SFP) was investigated by using the semi-circular bending(SCB) test in this paper. Thirteen grouting slurries were prepared. The compressive strength of these materials ranges from 3 to 100 MPa. The relationship between the compressive strength of the grouting slurry and the cracking property of SFP was obtained at different loading rates and different temperatures. The peak load, fracture energy(E), flexible index(FI), and cracking resistance index(CRI) were calculated to determine the material performance. The results show that the compressive strength of the grout influences the cracking behavior. With a higher comprehensive strength grouting slurry, the FI value of SFP decreased initially and then increased slightly at 25 ℃ in 50 mm/min. The CRI value decreased at the same time. E values changed just according to the test temperature and loading rate. The damage paths of SFP are different. The damage path of the SFP sample appears as diffuse damage at 1 mm/min at 60 ℃ or clean damage at 50 mm/min at 25 ℃. These findings indicate that there is a correlation between the compressive strength of grouting slurry and SFP cracking behavior. The cracking form is influenced by loading rate and temperature.

Helix-like structure formation of a semi-flexible chain confined in a cylinder channel

Molecular dynamics method is used to study the conformation behavior of a semi-flexible polymer chain confined in a cylinder channel.A novel helix-like structure is found to form during the simulation.Moreover,the detailed characteristic parameters and formation probability of these helix-like structures under moderate conditions are investigated.We find that the structure is not a perfect helix,but a bundle of elliptical turns.In addition,we conduct a statistical analysis for the chain monomer distribution along the radial direction.This research contributes to our understanding of the microscopic conformation of polymer chains in confined environments filled with a solvent.

Investigation of material composition,design,and performance of open-graded asphalt mixtures for semi-flexible pavement:A comprehensive experimental study

The primary goal of this study is the design and construction of semi-flexible pavement(SFP)mixture in accordance with the engineering and mechanical criteria.This study involves the use of a range of gradation curves,air void contents,cellulose and synthesized fibers,and neat and modified asphalt binders to prepare the open-graded asphalt(OGA)mixtures.To analyze the characteristics of these mixtures,a variety of test,namely binder drainage,semi-circular bending(SCB),Cantabro,wheel tracking,indirect tensile strength(ITS),and permeability tests were conducted.Additionally,to analyze the prepared grouting material,flexural strength,compressive strength,and fluidity tests were conducted.In the final stage,SFP was compared to HMA in terms of engineering characteristics and performance.According to the results,SFP was more resistant to skid,rutting,fire,and moisture damage,while HMA had a better performance in fracture tests,including SCB test.According to the results of the mechanical performance tests conducted on OGA mixtures,the highest and lowest values for air void content to achieve the highest mechanical performance level were 30%-35%and 25%,respectively.Also,based on the laboratory results,it was determined that the required void ratio for constructing OGA mixtures was 24%-26%based on the bitumen type and fibers amount in the mixture.Finally,SFP mixture can be regarded as a viable alternative to common pavements thanks to its high resistance to rutting and moisture damage,long freezing-thawing fatigue life,and adequate fire and skid resistance.

Compressed wormlike chain moving out of confined space: A model of DNA ejection from bacteriophage

The molecular biomechanics of DNA ejection from bacteriophage is of interest to not only fundamental biological understandings but also practical applications such as the design of advanced site-specific and controllable drug delivery systems. In this paper, we analyze the viscous motion of a semiflexible polymer chain coming out of a strongly confined space as a model to investigate the effects of various structure confinements and frictional resistances encountered during the DNA ejection process. The theoretically predicted relations between the ejection speed, ejection time, ejection length, and other physical parameters, such as the phage type, total genome length and ionic state of external buffer solutions, show excellent agreement with in vitro experimental observations in the literature.

Simulation Study on the Extension of Semi-flexible Polymer Chains in Cylindrical Channel

The scaling relations among the mean end-to-end distance of polymer along the channel<R||>,the polymer length N,and the effective diameter of channel De were investigated for flexible and semi-flexible polymer chains confined in long cylindrical channels.For the flexible polymer chain,scaling relation<R||>~NDe–0.7 was found in the classic de Gennes regime at lp2/b<De<Rg with lp the persistence length,b the bond length,and Rg the radius of gyration of polymer.For the semi-flexible polymer,<R||>~NDe–1 in the transition regime lp<De<xlp(x>1)and<R|>~De–0.7 in the classic de Gennes regime at larger De>xlp were observed.The simulation results revealed that the scaling relation in the transition regime was due to the rod-like behavior of the semi-flexible polymer in the small regime lp<De<xlp.

Development of high stability hot mix asphalt concrete with hybrid binder

Cost reduction of public works projects has been desired due to severe financial circumstances. Therefore, asphalt pavement has been requested to extend its life. Semi-flexible pavement or epoxy asphalt pavement, which has high rutting resistance and oil resistance, may be applied to the place where these performances are demanded. However, special technique is required in manufacturing and construction. In addition, these materials have also raised a problem that they cannot be recycled. Meanwhile, conventional asphalt pavement has several drawbacks. It is vulnerable to rutting caused by traffic load and damage caused by petroleum oils such as gasoline or motor oil. The materials used in asphalt mixtures were studied for improving the durability of asphalt mixture. A high stability asphalt concrete was developed which has equal or superior performance to semi-flexible pavement and epoxy asphalt pavement. In this paper, the process of selecting the substance and the characteristics evaluation of the developed mixtures are described. Furthermore, an inspection result as well as follow- up survey of the performance of the developed mixtures obtained from trial and actual construction is shown.