Anisotropic mechanical behavior

Fig. 13 Anisotropic mechanical behavior of a mPDMS sample containing 30 wt % magnetite. The arrows on the samples indicate the direction of compressive force...

LLM traditionally uses paper or plastics, but metals and ceramics are available as well. As an advantage, LLM processes all types of sheet materials. They are comparably inexpensive. The big amount of waste compensates this favor at least partly. Another disadvantage is the anisotropic mechanical behavior. 

Due to its surface texture and its anisotropic mechanical behavior, extrusion processes are not reconnnended for tooling, for neither Prototype nor Indirect or Direct Tooling. 

There exists anisotropic mechanical behavior for short carbon fiber reinforced composites. The fibers oriented along mechanical loading direction generally yield higher reinforcing efficiency than those perpendicular to the loading direction [33]. On the basis of the periodic-cell simulation for short-reinforced composites, Nishikawa et al. demonstrated... 

Blood vessels either delivering oxygenated blood - arteries, arterioles, capillaries or returning with carbon dioxide -veins and venules, display highly nonlinear elastic and anisotropic mechanical behavior and exhibit complex material properties [1,2],... 

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 1-4 and discussed in the following paragraphs. 

James Martin Whitney, A Study of the Effects of Coupling Between Bending and Stretching on the Mechanical Behavior of Layered Anisotropic Composite Materials, Ph.D thesis. Department of Engineering Mechanics, The Ohio State University, Columbus, Ohio, 1968. (Available from University Microfilms, Inc., Ann Arbor, Michigan, as no. 69-5000.)... 

Both E, in ideal solids, and rj, in ideal liquids, are material functions independent of the size and shape of the material they describe. This holds for isotropic and homogeneous materials, that is, materials for which a property is the same at all directions at any point. Isotropic materials are so characterized because their degree of symmetry is infinite. In contrast, anisotropic materials present a limited number of elements of symmetry, and the lower the number of these elements, the higher the number of material functions necessary to describe the response of the material to a given perturbation. Even isotropic materials need two material functions to describe in a generalized way the relationship between the perturbation and the response. In order to formulate the mechanical behavior of ideal solids and ideal liquids in terms of constitutive equations, it is necessary to establish the concepts of strain and stress. 

Fig. 14 Deviation from the ideal mechanical behavior for anisotropic magnetoelasts having different amounts of filler particles, as indicated in the figures. The cross-linker content was 3.5 wt % in every case...

The deformation parallel to the structure has a strong influence on the mechanical behavior because of the bending of the ordered structure. The anisotropic magnetite-loaded PDMS samples showed similar behavior under compression. 

Linear viscoelasticity is valid only imder conditions where structural changes in the material do not induce strain-dependent modulus. This condition is fulfilled by amorphous polymers. On the other hand, the structural changes associated with the orientation of crystalline polymers and elastomers produce anisotropic mechanical properties. Such polymers, therefore, exhibit nonlinear viscoelastic behavior. 

The structure and orientation of the reinforcing fibers in the matrix system are essential for the mechanical properties of the work-piece. The choice of a particular architecture is dependent on multiple factors like drapeabiUty of the fabric, geometry/shape of the workpiece, mechanical requirements, and manufacturing process. Compraients made of unidirectional layers (laminates) are showing the best mechanical properties since the fibers are completely stretched (no undulation). Usually the single layers of a laminate are showing different fiber orientations. This causes anisotropic material behavior in the planar direction. The structure of a multiaxial layered laminate is shown in Fig. 2. 

Mclamore, R., Gray, K. E. (1967). Mechanical behavior of anisotropic sedimentary rocks. Journal of Engineering for Industry, 89, 62-61. 

Buyanov AL, Gofman IV, Revel skaya LG, Khripunov AK, Tkachenko AA (2010) Anisotropic swelling and mechanical behavior of composite bacterial cellulose-poly(acrylamide or acrylamide-sodium acrylate) hydrogels. J Mech Behav Biomed Mater 3 102-111... 

Continuum shell models used to study the CNT properties and showed similarities between MD simulations of macroscopic shell model. Because of the neglecting the discrete nature of the CNT geometry in this method, it has shown that mechanical properties of CNTs were strongly dependent on atomic structure of the tubes and like the curvature and chirality effects, the mechanical behavior of CNTs cannot be calculated in an isotropic shell model. Different from common shell model, which is constmcted as an isotropic continuum shell with constant elastic properties for SWCNTs, the MBASM model can predict the chirality induced anisotropic effects on some mechanical behaviors of CNTs by incorporating molecular and continuum mechanics solutions. One of the other theory is shallow shell theories, this theory are not accurate for CNT analysis because of CNT is a... 

SINCE the discovery of liquid crystalline phenomenon for low molecular weight liquid crystals (LMWLCs) more than 100 years ago, anisotropic ordering behaviors of liquid crystals (LCs) have been of considerable interest to academe [1-8], In the 1950s, Hory postulated the lattice model for various problems in LC systems and theoretically predicted the liquid crystallinity for certain polymers [1-3], As predicted by the Hory theory, DuPont scientists synthesized lyotropic LCPs made of rigid wholly aromatic polyamide. Later, Amoco, Eastman-Kodak, and Celanese commercialized a series of thermotropic main-chain LCPs [2]. Thermotropic LCPs have a unique combination of properties from both liquid crystalline and conventional thermoplastic states, such as melt processibility, high mechanical properties, low moisture take-up, and excellent thermal and chemical resistance. Aromatic main-chain LCPs are the most important class of thermotropic LCPs developed for structural applications [2,4-7]. Because they have wide applications in high value-added electronics and composites, both academia and industry have carried out comprehensive research and development. 

Kwasniewski, A.M. 1993. Mechanical Behavior of anisotropic rocks. Comprehensive rock engineering, 1 285-312. Pergamon Press, Oxford. 

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