Young orientation dependence

Fig. 2.10. Orientation dependence of Young s modulus for some materials of table 2.3. In each spatial direction, the distance of the surface from the origin is a measure of Young s modulus...

In the uniaxially oriented sheets of PET, it has been concluded that the Young s modulus in the draw direction does not correlate with the amorphous orientation fa or with xa "VP2(0)> 1r as might have been expected on the Prevorsek model37). There is, however, an excellent correlation between the modulus and x,rans,rans as shown in Fig. 15. It has therefore been concluded 29) that the modulus in drawn PET depends primarily on the molecular chains which are in the extended trans conformation, irrespective of whether these chains are in a crystalline or amorphous environment. It appears that in the glassy state such trans sequences could act to reinforce the structure much as fibres in a fibre composite. 

Hardness 29.89 3.12 GPa (depending on crystal orientation) Compressive Strength 2730 MPa Young s Modulus 650 GPa Fracture Toughness 6.4 MPa m ... 

The state of conscious awareness, with orientation of self in time and space, depends on hnely tuned and accurately co-ordinated activity in multiple neuronal networks in the brain (Park Young, 1994). Such activity involves parallel processing in many cortical and subcortical pathways including arousal and memory systems (Chapters 3 and 4) and systems involved in mood (Chapters 5 and 18) and utilises an orchestra of many neurotransmitters. The whole ensemble appears to be synchronised by high frequency (40+ Hz) oscillatory electrical activity which binds the component parts together (Llinas et ah, 1998 Tallon-Baudry Bertrand, 1999). 

Delaminations can occur during cure as a result of high internal stresses. These stresses develop due to resin shrinkage and thermal volume changes. The level of stresses depend on several material properties, such as the Young s modulus, Poisson s ratio, and thermal expansion coefficients of both resin and fibers. In addition, the level of stresses also depends on several conditions, such as fiber orientation, fiber volume fraction, and part geometry. 

Recently, some models (e.g., Halpin-Tsai, Mori- Tanaka, lattice spring model, and FEM) have been applied to estimate the thermo-mechanical properties [247, 248], Young s modulus[249], and reinforcement efficiency [247] of PNCs and the dependence of the materials modulus on the individual filler parameters (e.g., aspect ratio, shape, orientation, clustering) and on the modulus ratio of filler to polymer matrix. 

In this expression, Ef and Em are the Young modulus of respectively the fiber and the matrix, and f is the fiber volume fraction. //0 is the fiber orientation factor this factor is equal to 1 for perfectly oriented fibers and 1/6 for a random orientation, tj, is the so-called effective length coefficient (10), which mainly depends on the aspect ratio of the fiber. Indeed ... 

The Young s moduli of the small-diameter extrudates were uniquely related to the extrusion ratio R to a very gocxl approximation. As shown in Fig. 19, this relationship does not depend on the molecular weight of the polymer, consistent with the second principle enunciated above. In fact, it appears from extensive studies of the structure and properties of oriented LPE, PP and POM that comparable materials are produced in large section by hydrostatic extrusion to those produced as fibres or tapes by tensile drawing. 

In this section, we follow Young (1980b) and first focus on a variant of the two-dimensional XY model, namely the plane rotator model where each lattice site i carries an unit vector (cos 6, sin0,-) and the Hamiltonian depends only on the relative orientations of these vectors,... 

All mechanical properties depend on crystallinity, orientation and crosslinking. These three factors will all be discussed in this chapter. See also Kinloch and Young [2] and van Krevclcn [71 for discussions on the effects of crystallinity and orientation on the mechanical properties. The discussion of the morphologies and the mechanical properties of multiphase polymeric systems (such as composites and blends) will be postponed to Chapter 19 and Chapter 20, respectively, where crystallinity and orientation will be discussed further in this broad context. 

Abstract. The intrinsic polarization of young stars contains important information about the physical state of the objects and their surroundings. In particularly, the investigations of polarimetric activity of the variable stars can throw light upon variability mechanisms. In stars surrounded by circumstellar disks unresolved with a telescope, the position angle of the intrinsic linear polarization can indicate disk orientation. The wavelength dependence of the linear polarization is a sensitive function of the optical parameters of the dust particles and can be used for their diagnostics. 

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