Uniaxial deformation behavior

Morphological changes induced by small uniaxial deformation 

In the preceding section, it was shown that, at relatively small deformations, the hard PA domains become activated and act as load-bearing structures. 

At the other compositional extreme (P7033), the PA content is high enough to allow the formation of a continuous spherulitic PA superstructure when the 

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Bicakci, E., Zhou, X. and Cakmak, M., Phase and uniaxial deformation behavior of ternary blends of poly(ethylene naphthalate), poly(ether imide) and poly(ether ether ketone), in Proceedings of the 55th SPE ANTEC 97 Conference, May 5-8, 1997, Toronto, ON, Canada, Society of Plastics Engineers, Brookfield, CT, 1997, Vol. 2, pp. 1593-1599. 

Model networks, synthesized by endlinking processes, contain few structural defects and are close to ideality. Spring-suspended bead models seem to fit adequately with the structural data obtained on labelled model networks and with the swelling and uniaxial deformation behavior of these networks. (67 refs.)... 

Figure 3. Uniaxial deformation behavior of a thin film PP-nylon composite. See text for the description of the sequence.

Koike Y, Cakmak M. The influence of molten fraction on the uniaxial deformation behavior of polypropylene Real time mechanoa optical and atomic force microscopy observations. J Polym Sci B 2006 44 925-941. 

Semicrystalline Segmented Poly (Ether-6-Amide) Copolymers Overview of Solid-State Structure-Property Relationships and Uniaxial Deformation Behavior... 

Since the introduction of PEBAX by Atochem, many research groups have devoted much effort in the study of the morphology and properties of these copolymers, in addition to other PEBA systems consisting of various polyamides, such as nylon 6, nylon 11, nylon 12, etc., and polyesters, such as PTMO, poly (ethylene oxide) (PEO), and poly(propylene oxide) (PPO). This chapter aims to present an overview of these materials its scope is limited to the solid-state structure-property relationships and uniaxial deformation behavior of the PEBA copolymers. It is divided into two main sections. PTMO-PA12 systems are first presented and, in the second section, systems based on PEO or PTMO... 

The structure-property behavior and the uniaxial deformation behavior of poly (ether-6-amide) copolymers have been reviewed in this chapter. Copolymers based on either aliphatic or aromatic (of uniform length) hard segments and PTMO or PEO as the soft segments were partially explored. These PEBA copolymers possess a complex morphology consisting of microphase-separated hard and soft phases. The extent of microphase separation in these materials is a function of the relative composition of the hard and soft phases and is also dependent on the segment molecular weight. 

Fig. 2.10. Characteristic uniaxial deformation behavior of polymers, a. brittle (PS at room-temperature), b. hard elastic (lamellar PP film), c. ductile (PVC at room-temperature), d. soft (PTFE at 100 °C).

Section II B of Chapter 2 gave a description of the uniaxial deformation behavior of an unoriented thermoplastic polymer. It was indicated that — depending on experimental and material parameters - failure could occur at any of the different stages of a tensile loading process ... 

A theoretical investigation of the use of NMR lineshape second moments in determining elastomer chain configurations has been undertaken. Monte Carlo chains have been generated by computer using a modified rotational isomeric state (RIS) theory in which parameters have been included which simulate bulk uniaxial deformation. The behavior of the model for a hypothetical poly(methylene) system and for a real poly(p-fluorostyrene) system has been examined. Excluded volume effects are described. Initial experimental approaches are discussed. 

The success of the developed model in predicting uniaxial and equi-biaxi-al stress strain curves correctly emphasizes the role of filler networking in deriving a constitutive material law of reinforced rubbers that covers the deformation behavior up to large strains. Since different deformation modes can be described with a single set of material parameters, the model appears well suited for being implemented into a finite element (FE) code for simulations of three-dimensional, complex deformations of elastomer materials in the quasi-static Emit. 

Here, we investigate the stress response to large uniaxial deformations of model single-protein films and protein plus surfactant mixed films. We show that the general structure of a compressed (expanded) protein film is very sensitive to the breakability of the protein-protein bonds. We then study the structural changes and mechanical response of a protein plus surfactant mixed film to large compression (expansion). We show that the nature of the protein-protein bond parameters also affects the overall displacement behavior of the coadsorbed surfactant during compression. 

Figure 22.2 General description of the uniaxial load/deformation behavior for (a) flexible plastics and (b) elastomers. Source Adapted with permission of John Wiley Sons, Inc., from Odian G. Principles of Polymerization. 4th ed. New York Wiley-Interscience 2004 [1].

Experimental creep data for ceramics have been obtained using mainly flexural or uniaxial compression loading modes. Both approaches can present some important difficulties in the interpretation of the data. For example, in uniaxial compression it is very difficult to perform a test without the presence of friction between the sample and the loading rams. This effect causes specimens to barrel and leads to the presence of a non-uniform stress field. As mentioned in Section 4.3, the bend test is statically indeterminate. Thus, the actual stress distribution depends on the (unknown) deformation behavior of the material. Some experimental approaches have been suggested for dealing with this problem. Unfortunately, the situation can become even more intractable if asymmetric creep occurs. This effect will lead to a shift in the neutral axis during deformation. It is now recommended that creep data be obtained in uniaxial tension and more workers are taking this approach. 

L J Zapas and J M Crissman, Creep and recovery behavior of ultra-high molecular weight polyethylene in the region of small uniaxial deformations . Polymer... 

An important issue is the influence of an electrochemical environment on the cyclic deformation behavior of metals [74,33-35]. As illustrated by the data in Fig. 1 for a carbon-manganese steel in high-temperature water, environment does not typically affect the relationship between stresses and strains derived from the maximum tensile (or compressive) points of steady-state (saturation) hysteresis loops [36]. Such loops should relate to elastic and plastic deformation prior to substantial CF microcracking. CF data of the sort shown in Fig, 1 are produced by either stress or total strain controlled uniaxial fatigue experiments, identical to the methods... 

Small angle neutron scattering (SANS) measurements were performed on poly(isoprene) networks at different uniaxial strains, i.e., 1,0 < X (extension ratio) <2.1. The networks were prepared from anionically polymerized, a, oo-dihydroxy-poly(isoprene) precursors (H-chains) and the corresponding poly(isoprene-dg) isotopic counterparts (D-chains), crosslinked in concentrated tetrahydrofuran solutions by trifunctional crosslinkers, tri-isocyanates. The two components of the radius of gyration of elastic strands, parallel and perpendicular to the strain axis, were determined from the vSANS data of the networks with 8% and 15% D-chains. Two molecular weights of D-chains, 26,000 and 64,000, crosslinked with approximately the same molecular weight H-chains (29,000 and 68,000 respectively) were examined for the deformation behaviors. 

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