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Mechanics of Composites
Published in Sumit Sharma, Composite Materials, 2021
Use of the two concepts of macromechanics and micromechanics allows the tailoring of a composite material to meet a particular structural requirement with little waste of material capability. The ability to tailor a composite material to its job is one of the most significant advantages of a composite material over an ordinary material. Perfect tailoring of a composite material yields only the stiffness and strength required in each direction, no more. In contrast, an isotropic material is, by definition, constrained to have excess strength and stiffness in any direction other than that of the largest required strength or stiffness. The inherent anisotropy (most often only orthotropy) of composite materials leads to mechanical behavior characteristics that are quite different from those of conventional isotropic materials. The behavior of isotropic, orthotropic, and anisotropic materials under loadings of normal stress and shear stress is shown in Figure 4.1 and discussed in the following paragraphs.
Selection of Materials to Resist Failure
Published in Mahmoud M. Farag, Materials and Process Selection for Engineering Design, 2020
Although many engineering materials are almost isotropic, there are important cases where significant anisotropy exists. In the latter cases, the strength depends on the direction in which it is measured. The degree of anisotropy depends on the nature of the material and its manufacturing history. Anisotropy in wrought metallic materials is more pronounced when they contain elongated inclusions and when processing consists of repeated deformation in the same direction. Composites reinforced with unidirectional fibers also exhibit pronounced anisotropy, which can be useful if the principal external stress acts along the direction of highest strength.
Anisotropic ferromagnet
Published in A.G. Gurevich, G.A. Melkov, and Waves, 2020
Anisotropy is a dependence of the properties of a substance or a body on the angles between the directions of applied fields and some preferred directions. These directions can be determined by the substance structure, by the shape of the body, or (if we consider the properties in ac fields) by the directions of some external steady fields. Two kinds of anisotropy were already treated in Chapter 1. First, the gyrotropy when the direction of the steady magnetization M0 was the preferred one, and the high-frequency magnetic susceptibility acquired the tensor form (1.42). Second, we have seen in Section 1.5 that the ferromagnetic-resonance conditions depend on the orientation of M0 relative to the ellipsoid axes. Such anisotropy can be referred to as the shape anisotropy. However, it was assumed throughout Chapter 1 that the substance itself (a ferromagnet), in the absence of steady magnetization, is isotropic.
Relationship among air void microstructural characteristics, stiffness, and fatigue of asphalt concrete mixtures
Published in Road Materials and Pavement Design, 2022
Thiago Delgado de Souza, Alexis Jair Enríquez-León, Patrícia Hennig Osmari, Larissa Montagner de Barros, Alex Duarte de Oliveira, Francisco Thiago Sacramento Aragão, André Maués Brabo Pereira
Anisotropy can be defined as the variation of the material physical properties when they are measured in different directions. In this paper, the degree of anisotropy is defined as a 3D structural symmetry parameter that determines the presence or absence of a preferential alignment of structures along a particular direction. This characteristic may significantly affect the mechical responses of the materials (Choudhary et al., 2019; Kastner et al., 2021 Odgaard, 1997). It can be obtained using the decomposition of the anisotropy tensor, resulting in eigenvalues and eigenvectors, which are related to the material lengths and orientation, regarding the different axes. Equation (3) (Odgaard, 1997) was used to quantify the degree of anisotropy for the air voids. It is worthy to mention that a degree of anisotropy of 0 characterises a material hypothetically isotropic, while a value of 1 represents a totally anisotropic sample.
Chebyshev pseudospectral method in the reconstruction of orthotropic conductivity
Published in Inverse Problems in Science and Engineering, 2021
Everton Boos, Vanda M. Luchesi, Fermín S. V. Bazán
Materials whose physical properties, such as elasticity moduli, Poisson coefficients, heat conductivity, etc., vary depending on spatial orientation of the physical body are referred to as anisotropic, while those materials that do not change with spatial orientation are referred to as isotropic [1]. Orthotropic material is a type of the anisotropic material whose characteristics remain unchanged along its planes of elastic symmetry. In nature, there are many materials that can be considered anisotropic such as crystal, woods, geological sediments and biological tissues. With the advent of new technologies, new anisotropic materials have been manufactured by industrial engineering, making it necessary to know their driving properties. These properties can be roughly defined by the difference in physical material or mechanical attributes when measured along different axes, such as absorbance, refraction, conductivity, tensile strength, etc.
Post-processing treatments to enhance additively manufactured polymeric parts: a review
Published in Virtual and Physical Prototyping, 2021
F. Tamburrino, S. Barone, A. Paoli, A. V. Razionale
Mechanical properties are also affected by anisotropy. The layer-by-layer approach introduces directional dependencies of the mechanical behaviour of the printed parts, which may exhibit lower tensile strength along the Z-direction (build direction) than the X–Y direction (in plane), as shown in Figure 1-e. The fracture occurs in correspondence to the layer interface, which represents the weak point due to the layer-to-layer bond (Torrado et al. 2015). For ME, anisotropy is one of the most significant factors in comparison to the other AM technologies, and it is influenced by the building direction, layer thickness, layer width, airgap, raster pattern, and angle (Dizon et al. 2018). For VAT, anisotropy is typically very low (approximately 1%), and it is influenced by layer thickness, post-curing carried out at various wavelengths, and thermal treatments carried out at different temperatures and durations (Dizon et al. 2018). The anisotropy for PBF is relatively low (approximately 10%), and it is influenced by energy density, laser beam speed, part orientation, layer thickness, bed temperature, and hatch pattern. The control of polymer powder in terms of shape, size, and distribution also plays a crucial role (Caulfield, McHugh, and Lohfeld 2007). The anisotropy of BJ can be ascribed to the same factors that affect PBF, but its significance can be increased by the higher porosity and hygroscopicity. The anisotropy for MJ (approximately 2%) is similar to that observed for VAT. This can be ascribed to the high homogeneity of parts produced by MJ and VAT, which show low porosity.