Papers by Keyword: Shear Modulus

Abstract: A 3D Carbon-Carbon (Cf/C) composite with fabric reinforcement is of interest in applications where flexural loads are dominant, such as in the wings and control surfaces of aircraft and missile systems. Investigating the mechanical properties of these composites is crucial for understanding their performance, especially for designing and analysing composite structures used in extreme conditions. In this research paper, the compression and shear responses of the 3D PF Cf/C composite samples have been determined at room temperature. The samples were machined in the directions of XY, XZ, and ZX, respectively. Then, the Iosipescu shear test and the short beam shear test were employed to evaluate the shear strength and shear modulus of the composite samples, respectively. The material exhibits a strain to failure of around 0.15% in the X direction with a modulus of 54 GPa. In the Z direction, it deforms more, with a strain to failure of approximately 20% and a modulus of 6.2 GPa.

Abstract: Determining interlayer shear modulus of composite materials by the method of three-point transverse bending is considered, and Timoshenko approaches to estimating the shear strains in this type of loading are assessed. It is shown that these approaches make it possible to determine the shear component of beam deflection with an accuracy acceptable for practice in testing them in three-point transverse bending, but only for isotropic materials. For anisotropic materials, they are unacceptable. These approaches are also unacceptable for determining the shear modulus of isotropic and anisotropic materials. Based on the data obtained as a result of the study, a simple and economical method for determining the shear moduli in the three-point transverse bending is proposed. This method was tested on both isotropic and composite materials with different reinforcement structures. Results showed a good agreement between the calculated and experimental values of the shear moduli for all the materials considered, which confirmed that the method proposed method can be used in practice.

Abstract: The usage of reinforcing fibers extracted from nature is increasing in the present decade due to increasing the demand for biodegradability and environmentally friendly materials. In this paper, biodegradable sisal fiber and corn starch powder mixed thermoset and thermoplastic composite are prepared and tested for Young’s modulus. The effect of sisal fiber weight fraction on the Young’s modulus is identified at constant content of corn starch powder. Later, using Micromechanics approach and Finite Element Method simulation studies are performed to estimate transverse Modulus, Shear modulus, major and minor Poisson’s ratio of the sisal and starch based polymer composites. It is found that the composites prepared with sisal fiber and corn starch powder are a promising replacement for plastic reinforced composite to promote the biodegradability, especially under high weight fraction of sisal fiber

Abstract: The motion of a rigid sphere located at tissue-mimicking material interface in response to a dynamic force of short duration for the purpose of the determination of material viscoelastic properties was investigated in this study. The experiments were performed using a rigid sphere located at tissue-like material (gelatin phantom) interfaces. An electromagnet was used to apply the desired dynamic force to the sphere and a high-speed camera was used to track the movement of the sphere. Using the experimentally measured response of the sphere and the dynamic response of the sphere predicted by a sophisticated analytical model of the sphere located at a medium interface, the shear modulus, density and damping of the tissue-mimicking material were determined. The procedure followed in this study successfully produced the shear modulus, density and viscous damping ratio of the 20% (and 30%) gelation phantom as 1320 Pa, 1040 kg/m³ and 0.12 (and 2580 Pa, 1180 kg/m³ and 0.2), respectively. As the sophisticated theoretical model that is valid for small and large sphere displacements includes many parameters for the system such as the mass and size of the sphere, the inertia force of the medium involved in motion and the radiation damping due to shear waves and the experimental setup is very straightforward, it is believed that the procedure proposed in this study can be widely exploited to identify accurate material viscoelastic properties in practice.

Abstract: As a result of the research, the deformation properties of aluminosilicate adhesives modified with nitrate salts and intended for gluing wooden products and structures made of pine, beech and oak wood at different stages of their hardening were determined. Considering that pine is the most common wood in the manufacture of products and structures, then in order to reduce the numerical values of the elastic modulus in glued materials, it is advisable to add ammonium, lithium and sodium nitrates in an amount of 0.5%, potassium nitrate in an amount of 1% into the composition of an aluminosilicate adhesive. which will ensure the approximation of the elastic modulus values to the values of the unmodified aluminosilicate adhesive and will significantly affect the water resistance of the glue joint and the depth of penetration of the adhesive into the wood structure. For gluing beech wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% ammonium and potassium nitrates and 1% lithium and sodium nitrates, which will reduce the numerical values of the elastic modulus in glued materials by 1.18 and 1.53 times compared with the values of the elastic modulus of the unmodified aluminosilicate adhesive. For gluing oak wood products to reduce the elasticity modulus, it is advisable to introduce 0.5% potassium nitrate and 1.5% sodium nitrate, which will reduce the numerical values of the elastic modulus in glued materials by 1.4 and 2.83 times compared to the values modulus of elasticity of unmodified aluminosilicate adhesive.

Abstract: In this paper we report on investigation of the viscoelastic and rheological properties of early synthesized and characterized nanosuspensions by acoustical method, allowing to obtain the characteristic curves of shear elastic moduli and to assess the degree of "hardening" and structuring of the suspension. The paper is rising the question of fundamental problem - the structuring the nanosuspension, that might shed a light on the possibility of "engineering" the structure of a liquid by controlling and regulating the degree and nature of intermolecular interaction.

Abstract: Following the fundamental work by Bazaron, Bulgadaev and Derjaguin [6] on the observation of shear elasticity of low viscous liquids, we build on this study by examining viscous liquids, polymers and suspensions of nanoparticles. In this paper, we review our past and current efforts in these areas. The mechanical properties of liquids, polymers and nanosuspensions have been studied at relatively low frequencies of 10⁵ Hz. The real and imaginary shear moduli of these samples were obtained on equipment using the acoustic resonance technique. It was shown that the shear modulus and viscosity decreases with increasing shear deformation. The behavior of viscoelastic fluids near surfaces is similar to that of colloidal and polymer suspensions, suggesting that the liquid component is determined by the mechanical response of suspensions.

Abstract: The contribution is focused on estimating the shear modulus of the samples of circular and hollow circular sections by static method. The samples were loaded by simple torsion, individual sections were stressed by shear stress. Theoretical basis are determined by linear elasticity and strength theory and they define the relation between shear modulus, maximum shear stress and relative strains. Relative strains are determined by using measurement apparatus and measurement system Quantum X MX 840.

Abstract: Shear properties and shear modulus of an advanced 3D multi-layer glass reinforced polyester thermoformed composite material to be used for manufacture of selected car body components were evaluated. The experimental methodology is described in detail and some aspects like effects of extensometer gauge length or minimum material macrostructure length unit on final results are analysed and discussed. Shear modulus values of the material are presented.

Abstract: The resonant column method is established as a standard laboratory method for the study of the elastic properties of soils. The study presents low-amplitude resonant column test results on volcanic sands with intra-particle voids. The experiments were performed on dry samples prepared at variable relative densities and tested in torsional mode of vibration. In the first part of the article, the important factors that control the elastic stiffness of uncemented sands are described shortly and recent findings on granular soils dynamic properties are presented briefly. The second part describes the basic features of the resonant column used in the investigation and the materials of the study and in the third part representative results of an extensive experimental testing program on volcanic granular soils are presented and discussed with a focus on comparisons between the elastic stiffness of volcanic and quartz granular soils. The importance of the effect of the presence of intra-particle voids within the particle mass of the volcanic soils is emphasized, which in turn affects markedly the global void ratio of the samples.