Structure/property material behavior

In this chapter, we will review the effects of shock-wave deform.ation on material response after the completion of the shock cycle. The techniques and design parameters necessary to implement successful shock-recovery experiments in metallic and brittle solids will be discussed. The influence of shock parameters, including peak pressure and pulse duration, loading-rate effects, and the Bauschinger effect (in some shock-loaded materials) on postshock structure/property material behavior will be detailed. 

Materials science is concerned with the structure of materials, the binding forces that hold materials together, and the relation between structure, properties, and behavior. Two types of structure may be distinguished—atomic structure and microscopic structure. 

This book comprehensively covers aU aspects of SPS, from the synthesis of this new polymer by coordination polymerization to the characterization of structure, properties, and behavior of the neat material as well as of plastic materials, including the different processing opportunities of such materials, to the widely diversified applications of polymers and blends, also considering SPS-based polymers. 

Influence of Shock-Wave Deformation on the Structure/Property Behavior of Materials... 

To illustrate the effect of radial release interactions on the structure/ property relationships in shock-loaded materials, experiments were conducted on copper shock loaded using several shock-recovery designs that yielded differences in es but all having been subjected to a 10 GPa, 1 fis pulse duration, shock process [13]. Compression specimens were sectioned from these soft recovery samples to measure the reload yield behavior, and examined in the transmission electron microscope (TEM) to study the substructure evolution. The substructure and yield strength of the bulk shock-loaded copper samples were found to depend on the amount of e, in the shock-recovered sample at a constant peak pressure and pulse duration. In Fig. 6.8 the quasi-static reload yield strength of the 10 GPa shock-loaded copper is observed to increase with increasing residual sample strain. 

While the structure/property behavior of numerous shock-recovered metals and alloys has received considerable attention in the literature to date, the response of ceramics, cermets, and other brittle solids (including geological materials) to shock loading remains poorly understood [9], The majority of shock-recovery studies on brittle materials have concentrated on examining... 

Designers of most structures specify material stresses and strains well within the pro-portional/elastic limit. Where required (with no or limited experience on a particular type product materialwise and/or process-wise) this practice builds in a margin of safety to accommodate the effects of improper material processing conditions and/or unforeseen loads and environmental factors. This practice also allows the designer to use design equations based on the assumptions of small deformation and purely elastic material behavior. Other properties derived from stress-strain data that are used include modulus of elasticity and tensile strength. 

Multilayered materials owe their properties and behavior to the properties of and the interactions between the components (5). Each of the two or more components contributes its particular property to the total performance of the multilayered material. For example, in Pouch 1, Table II, the aluminum foil provides high oxygen and water vapor permeability resistance, poly (ethylene terephthalate) provides structural strength and stiffness, and the ethylene-butene copolymer provides a heat sealable layer. If the components of the multilayered materials interact then the whole would be something different than the sum of its parts. In other words, the properties of the components of the multilayered materials are not independent of one another but rather are interdependent. 

Polyethylene s simplicity of structure has made it one of the most thoroughly studied polymeric materials. With an estimated demand of close to 109 billion pounds in 2000 of the homopolymer and various copolymers of polyethylene,24 it is by far the world s highest volume synthetic macromolecule. Therefore, it is still pertinent to study its structure-property relationships, thermal behavior, morphology, and effects of adding branches and functional groups to the polymer backbone. 

Material properties at a critical point were believed to be independent of the structural details of the materials. Such universality has yet to be confirmed for gelation. In fact, experiments show that the dynamic mechanical properties of a polymer are intimately related to its structural characteristics and forming conditions. A direct relation between structure and relaxation behavior of critical gels is still unknown since their structure has yet evaded detailed investigation. Most structural information relies on extrapolation onto the LST. 

Many techniques ideally suited for nanostructure characterization unfortunately depend also on the substrate properties. For example, the reflectivity and conductivity of a substrate play an important role in the successful execution of the instrumental method. Hence, substrate-independent techniques are needed so that structure and/or behavior of the material can be investigated in a confined geometry, decoupled from the potentially invasive effect of the substrate-mate-rial interface. 

It has grown increasingly apparent that the non-crystalline portions of cellulose structures may play as important a role in the properties and behavior of cellulosic materials as the crystalline parts. X-ray diffraction studies have greatly extended knowledge of crystalline cellulose but in the case of the amorphous or disordered fraction the methods of study have necessarily been indirect and not completely reliable. 

Polymers vary from liquids and soft rubbers to very hard and rigid solids. Many structural factors determine the nature of the mechanical behavior of such materials. In considering structure-property relationships, polymers may be classified into one of several regimes, shown in the volume-temperature plot (Fig. 23.1). 

The dynamic mechanical thermal analyzer (DMTA) is an important tool for studying the structure-property relationships in polymer nanocomposites. DMTA essentially probes the relaxations in polymers, thereby providing a method to understand the mechanical behavior and the molecular structure of these materials under various conditions of stress and temperature. The dynamics of polymer chain relaxation or molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of polymeric macromolecules. The temperature dependence of molecular mobility is characterized by different transitions in which a certain mode of chain motion occurs. A reduction of the tan 8 peak height, a shift of the peak position to higher temperatures, an extra hump or peak in the tan 8 curve above the glass transition temperature (Tg), and a relatively high value of the storage modulus often are reported in support of the dispersion process of the layered silicate. 

We conclude from this discussion that a very complex correlation between structure and photoelectrochemical behavior is to be expected and it will often be difficult to decide what may be the main influence. The following examples are selected under the aspect to demonstrate some effects of surface orientation and crystal imperfections in systems where they are very pronounced. Materials with a large anisotropy of the crystal properties are the best candidates for this purpose. Therefore semiconductors with layer structure which have been introduced into photoelectrochemical studies by Tributsch (11,12,13) are predominantly used as examples. 

R. Bartnikas, "Engineering Dielectrics Vol. IIA—Electrical Properties of Solid Insulating Materials Molecular Structure and Electrical Behavior," ASTM... 

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