Effects Of Modulus Ratio Research Articles

Experimental study of the feasibility of using anhydrous sodium metasilicate as a geopolymer activator for soil stabilization

This paper presents recent research on the use of anhydrous sodium metasilicate (ASM) powder as the alkaline activator of a one-part geopolymer binder for use in soil stabilization, to enhance the strength properties of soft clay. Geotechnical, mineralogical and microstructural tests were used to determine the performance of the geopolymer binder when mixed into an artificial soft clay. Comparison with the strength development of geopolymer-stabilized clay samples activated by a conventional sodium hydroxide activator and the ASM activator had been made. The effects of modulus ratio (SiO2/Na2O), content of the activators, as well as the GGBS content, water content, and curing time on the strength development of the geopolymer-stabilized clay samples were evaluated. The results indicate that the ASM powder alone is suitable as an alkaline activator to generate a one-part geopolymer binder for soil stabilization based on its high 28-d strength (4.2MPa) and its modulus ratio, which was in the optimal range (0.9–1.2). The microstructural analyses confirm the influence of the two-stage dissolution process of the hydrated amorphous alkali metal silicate powders on the strength development of the ASM-powder clay samples and the formation of the geopolymer gels. This study demonstrates that the ASM powder can be used to substitute for sodium hydroxide in generating a geopolymer binder, which can lead to more practical applications for geopolymer in soil stabilization.

Proof and Control of Structural Modulus Gradient for Pure Flexible Pavement

Flexible base asphalt pavement was gradually applied in high-grade highway recently. Whether pavement is designed properly directly affects operating life and durability. Proper modulus gradient-controlling of structural layers was useful for structure stress. In order to further verify the necessity of modulus gradient-controlling of structural layers, the paper chose modulus ratio between base and surface affecting stress distribution of structure most obviously as entrance point, set interlayer binding condition as not fully continuous and then comprehensively calculated the mechanical responses of flexible pavement with modulus ratio between base and surface changing by shell designing software Bisar3.0, so the effect of modulus ratio was quantified. The results showed that when modulus ratio between base and surface changed from 8 to 14, maximum flexible strain of asphalt layer and maximum flexible stress of structure both showed the trend of increasing, at the same time shear stress of surface decreased; Controlling flexible stress and shear stress together and taking higher value of base module in proper scale was good for structure to keep mechanical balancing. It was suggested to control modulus gradient-controlling of structural layers at the scale from 8 to 10.

Vibration analysis of a specially orthotropic composite laminate with rectangular cutout using independent coordinate coupling method

In this paper, the independent coordinate coupling method is further developed and applied for solving the free vibration of a specially orthotropic composite laminate with rectangular cutout. The total energies of the laminate with cutout are calculated by subtracting the energies of the cutout domain from the energies of the laminate domain, where the energies of laminate domain and cutout domain are calculated independently. The mode shape functions of beams with various boundary conditions are considered in each direction as admissible functions. Two coordinate systems are coupled by imposing the displacement matching condition at the cutout domain. So it is very convenient to construct and calculate the mass and stiffness matrices. The effects of modulus ratio, aspect ratio and boundary conditions on the natural frequencies are investigated. The numerical results demonstrate that the proposed methodology can be used as an efficient tool to solve the free vibration problems of specially orthotropic composite laminates with rectangular cutout.

Effects of modulus ratio and dosage of alkali-activated solution on the properties and micro-structural characteristics of alkali-activated fly ash mortars

This study investigates the properties and micro-structural characteristics of alkali-activated fly ash (AAFA) mortars. Sodium oxide (Na2O) dosages of 121 and 150kg/m3 and liquid sodium silicate with alkaline modulus ratios (mass ratio of SiO2 to Na2O) of 1.23 and 0.8 were prepared as activators. Three alkaline solution to binder ratios of 0.35, 0.5, and 0.65 were selected to cast AAFA mortars. Compressive strength test, drying shrinkage test, water absorption test, initial surface absorption test, mercury intrusion porosimetry test (MIP), scanning electron microscopy (SEM) and X-ray diffraction analysis were conducted and their performance was discussed and compared with reference mortars produced with ordinary Portland cement (OPC). Test results show that both alkaline modulus ratio and the dosage of Na2O are two significant factors influencing the characteristics of AAFA mortars. The higher alkaline modulus ratio and dosage of Na2O are, the superior properties of AAFA mortars achieved. SEM and XRD demonstrate that the activation products of AAFA mortars are mainly amorphous alkaline aluminosilicate gels, which are attributed to the compressive strength. Under the alkaline modulus ratio of 1.23 and liquid/binder ratio of 0.5, AAFA mortars with Na2O dosage of 150kg/m3 may be considered as the optimum mix design based on the results.

Hygrothermal Effects on the Buckling of Laminated Composite Plates with Random Geometric and Material Properties

The combined effects of temperature and moisture on the buckling of laminated composite plates with random geometric and material properties are investigated. A C0 finite element based on higher order shear deformation theory has been used for deriving the standard eigenvalue problem. The random material and geometric properties are modeled as basic random variables. A Taylor series based mean-centered first order perturbation technique is used to find mean and standard derivation of the hygrothermal buckling loads of laminated composite plates subjected to uniform temperature and moisture rise with different boundary conditions. The effects of modulus ratio, fiber orientation, length to thickness ratio, aspect ratio, and boundary conditions on the hygrothermal buckling are analyzed. It is found that a small amount of material and geometric variations of the composite plate significantly affect the hygrothermal buckling loads. The results have been validated with independent Monte Carlo simulations and those are available in literature.

Thermal buckling of laminated composite plates

The thermal buckling of laminated composite plates is analysed using the finite element method based on the Reissner-Mindlin first order shear deformation theory. The nine-node Lagrangian isoparametric element is employed for the thermal buckling analysis of symmetric cross-ply, symmetric angle-ply and quasi-isotropic laminates subjected to uniform temperature distribution. The effects of modulus ratio, fibre orientation, length to thickness ratio, aspect ratio and various boundary conditions on the critical temperature are analysed. The influence of the stress distribution on the variation of the critical temperature with fibre orientation is studied for different boundary conditions. Also, the variation of critical temperature with shear correction factor is considered.

Effect of modulus ratio on stress near a discontinuous fiber

The effect of the fiber to matrix modulus of elasticity ratio varying from 1.0 to 200 was investigated for a two-dimensional plane-stress composite configuration having a simulated fiber volume fraction of 0.45 and containing a discontinuous fiber. Uniaxial loading parallel to the fibers was considered. Two independent techniques were used: moire strain analysis and finite-element analysis. Displacements were measured from four experimental models by utilizing optical fringe-multiplication techniques. The finite-element method yielded stresses which agreed closely with those obtained from the experimental analysis. Matrix stress-concentration factor near the discontinuous fiber was found to increase rapidly with increasing modulus ratio, reaching a value of 20 for a modulus ratio of 200. The finite-element method was shown to be a valuable tool for micromechanical stress analysis of composite materials, and the accuracy of strain analysis by moire-fringemultiplication techniques was demonstrated for problems containing sever strain gradients.