Polymer under tensile load

The most extensive ESR studies of polymers under tensile load have undoubtedly been carried out on drawn crystalline fibres, and this work has been reviewed recently by Kausch and De Vries It is clear that the morpholines of oriented crystalline fibres, with extensive tie-chain populations and hn d rees of molecular uncoiling, strongly favour the incidence of molecular hracture under tensile stress. 

Acoustic Emission of Polymers under Tensile Load... 

Polymers Under Tensile Load - Adv. Polymer Sci. Engineering, Ed. by K. D. Pae, D. R. Morrow, and Y. Chen, Plenum Press,... 

For polyurethane production, Donnelly [109] has carried out the synthesis of copolyurethanes based on mixtures of commercial poly(THF diol)s with glucose. Complex products resulted, which can be represented by mono- or bis(glucoside) structures. From a variety of polyol blends, solid polyurethanes were prepared which ranged from linear, soluble, weak elastomers to polymers of higher transition temperature and stiffness, low solubility, and low extension under tensile load [110]. 

Under tensile loading, the stress concentrating effect of an unbonded spherical particle is dmilar to that of a void. Nicolais and co-workers have studied the tensile stress-strain behaviour of composites based on SAN, ABS, PPO, and epojgr resins " 4-36) jjj jj g g polymers, unbonded glass beads cause yielding... 

Fig. 36. Comparison of cr—N curve under a square-wave loading with creep-rupture data for a typical ABS polymer (175). Note that the creep-rupture time scale is equivalent to that of the fatigue cycle scale in terms of time under tensile load. To convert MPa to psi, multiply by 145.

Angus C C L, Cheng J J R, Michael C H Y and Gaylene D K (2007), Repair of steel structures by bonded carbon fibre reinforced polymer patching experimental and numerical study of carbon fibre reinforced polymer-steel double-lap joints under tensile loading . Can J Civil Eng, 34(12), 1542-1553. 

Potschke P, Bhattacharyya A R and Janke A (2003) Morphology and electrical resistivity of melt mixed blends of polyethylene and carbon nanotube filled polycarbonate. Polymer 44 8061-8069. Yu M F, Lourie 0, Dryer M J, Molor K, Kelly T F and Ruoff R S (2000) Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load. Science 287 637-640. 

Until relatively recently, the use of quantum MD for modeling polymers seemed completely unrealistic. This approach, however, is now applicable to polymeric systems that could only be studied by means of empirical and semiempirical methods a decade ago. First-principles MD simulations have been successfully applied to a wide variety of important problems in polymer physics and chemistry and are now beginning to influence biology as well. ° Representative examples include the simulations of polyethylene (PE) (the prediction of Yoimg s modulus for crystalline material, strain energy storage and chain mpture under tensile load, the... 

Rgurel.18 Different deformation zones in polymers under tension loading, showing tensile bars after loading and the light optical appearance of the deformation area (left), as well as schematic illustrations of the micromechanical structures and macromolecular mechanisms (right)... 

Figure 2 shows the general test set-up of the two-material sample under tensile load with the coordinate systems irsed for calcirlation of the stress distribution along the interface. Two polymer mat ials are bonded by a curved interface with the cylindrical coordinates r=r and 6. Because of symmetry, only half of the sample needs to be considered, i.e., 0 < jc < a and 0 < 0< 90 . By choosing different radii r, different curvatures of the line and consequently different angles 0, respectively 02, can be realized at.r = a. The geometrical situation near the points = a is shown at the right hand side of Figure 2. If the curvature of the interface in the very vicinity of that point is neglected, the typical open wedge problem of two-material interfaces is faced.

The mechanical properties of plastics materials may often be considerably enhanced by embedding fibrous materials in the polymer matrix. Whilst such techniques have been applied to thermoplastics the greatest developents have taken place with the thermosetting plastics. The most common reinforcing materials are glass and cotton fibres but many other materials ranging from paper to carbon fibre are used. The fibres normally have moduli of elasticity substantially greater than shown by the resin so that under tensile stress much of the load is borne by the fibre. The modulus of the composite is intermediate to that of the fibre and that of the resin. 

It hag been shown that transition of a backbone carbon from the sp to sp state is promoted by tensile stresses and inhibited by compressive strains (10,44). The acceleration of the process of ozone oxidation of the polymers under load is not associated with the changes in supramolecular structure or segmental mobility of the chain. The probably reason of this effect is a decreasing of the activation energy for hydrogen abstraction (44). The mechanism of initial stages of the reaction of ozone with PP can be represented as ... 

TMA measures the mechanical response of a polymer looking at (1) expansion properties including the coefficient of linear expansion, (2) tension properties such as measurement of shrinkage and expansion under tensile stress, i.e., elastic modulus, (3) volumetric expansion, i.e., specific volume, (4) single-fiber properties, and (5) compression properties such as measuring the softening or penetration under load. 

Figure 5.92 Schematic illustration of fiber in polymer matrix (a) in the undeformed state and (b) under a tensile load. Horizontal lines are shown to demonstrate strain distribution. Reprinted, by permission, from N. G. McCrum, C. P. Buckley, and C. B. Bucknall, Principles of Polymer Engineering, 2nd ed., p. 242. Copyright 1997 by Oxford University Press.

Unlike ductile metals, composite laminates containing fiber-reinforced thermosetting polymers do not exhibit gross ductile yielding. However, they do not behave as classic brittle materials, either. Under a static tensile load, many of these laminates show nonlinear characteristics attributed to sequential ply failures. One of the difficulties, then, in designing with laminar composites is to determine whether the failure of the first ply constitutes material failure, termed first-ply failure (FPF), or if ultimate failure of the composite constitutes failure. In many laminar composites, ultimate failure occurs soon after first ply failure, so that an FPF design approach is justified, as illustrated for two common laminar composites in Table 8.9 (see Section 5.4.3 for information on the notations used for laminar composites). In fact, the FPF approach is used for many aerospace and aircraft applications. 

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