Other Micromechanics

Shock-wave compression is also used to study solid-solid phase transformation. Bancroft et al. [58] report a previously unknown phase transformation 

Twinning is itself a kind of solid solid phase transformation with the first and seeond phases having the same erystal strueture (henee the same pressure-volume response) but with prineipal erystallographie orientation at some angle to the original orientation. This results in a eontribution to plastie shear deformation under both quasi-statie and shoek-wave eonditions [61]. 

The preferred erystallographie strueture is determined by the Gibbs free energy, whieh is defined as 

The former is a question involving equilibrium thermodynamies and the latter is elosely related to the mieromeehanieal aetion of defeets. Grady [62] addresses both of these issues in a summary of mierostruetural effeets on wave propagation in solids. 

The motion of disloeations under eonditions of shoek-wave eompression takes plaee at sueh high veloeities (approaehing the elastie sound speed) that many vaeaneies and interstitials are left behind. However, these point defeets ean anneal out at room temperature and are thus diflieult to study by shoek-reeovery teehniques. The presenee of point defeets has little effeet on the material eompressibility and other properties related to equation of state. While they also have little direet influenee on the relief of shear stresses, point defeets do influenee the mobility and multiplieation of disloeations. This, in turn, affeets most of what happens under shoek-wave loading eonditions. 

---

Other aspects of interfacial science and chemistry are examined by Owen and Wool. The former chapter deals with a widely used chemistry to join disparate surfaces, that of silane coupling agents. The latter chapter describes the phenomenon of diffusion at interfaces, which, when it occurs, can yield strong and durable adhesive bonds. Brown s chapter describes the micromechanics at the interface when certain types of diffusive adhesive bonds are broken. The section on surfaces ends with Dillingham s discussion of what can be done to prime surfaces for adhesive bonding. 

Other researchers have substantially advanced the state of the art of fracture mechanics applied to composite materials. Tetelman [6-15] and Corten [6-16] discuss fracture mechanics from the point of view of micromechanics. Sih and Chen [6-17] treat the mixed-mode fracture problem for noncollinear crack propagation. Waddoups, Eisenmann, and Kaminski [6-18] and Konish, Swedlow, and Cruse [6-19] extend the concepts of fracture mechanics to laminates. Impact resistance of unidirectional composites is discussed by Chamis, Hanson, and Serafini [6-20]. They use strain energy and fracture strength concepts along with micromechanics to assess impact resistance in longitudinal, transverse, and shear modes. 

Shear-stress-shear-strain curves typical of fiber-reinforced epoxy resins are quite nonlinear, but all other stress-strain curves are essentially linear. Hahn and Tsai [6-48] analyzed lamina behavior with this nonlinear deformation behavior. Hahn [6-49] extended the analysis to laminate behavior. Inelastic effects in micromechanics analyses were examined by Adams [6-50]. Jones and Morgan [6-51] developed an approach to treat nonlinearities in all stress-strain curves for a lamina of a metal-matrix or carbon-carbon composite material. Morgan and Jones extended the lamina analysis to laminate deformation analysis [6-52] and then to buckling of laminated plates [6-53]. 

In this paper we approach the integrated optical sensors from the science/technological side. In that way it is avoided to discuss also all kinds of other competing sensing fields, in which the sensors are based on non-optical physical phenomena and are implemented as e.g. electrical, micromechanical or acoustical sensors. 

Sensors for measurements of physical parameters such as pressure, rotation or acceleration are commonly based on elongation or vibration of membranes, cantilevers or other proof masses. The electrochemical processes used to achieve these micromechanical structures are commonly etch-stop techniques, as discussed in Section 4.5, or sacrificial layer techniques, discussed in Section 10.7. 

Three-dimensional (3D) structuring of materials allows miniaturization of photonic devices, micro-(nano-)electromechanical systems (MEMS and NEMS), micro-total analysis systems (yu,-TAS), and other systems functioning on the micro- and nanoscale. Miniature photonic structures enable practical implementation of near-held manipulation, plasmonics, and photonic band-gap (PEG) materials, also known as photonic crystals (PhC) [1,2]. In micromechanics, fast response times are possible due to the small dimensions of moving parts. Femtoliter-level sensitivity of /x-TAS devices has been achieved due to minute volumes and cross-sections of channels and reaction chambers, in combination with high resolution and sensitivity of optical con-focal microscopy. Progress in all these areas relies on the 3D structuring of bulk and thin-fllm dielectrics, metals, and organic photosensitive materials. 

The commercial composite materials being marketed today are optimized in order to make the interfacial properties acceptable in the sense that they will not fail at such low levels as to detract from the overall composite behavior. Considering a unidirectional specimen, where the fibers are all aligned parallel to each other, commercial systems can be described by a rule of mixtures661 relationship (Fig. 10). Properties of the matrix and fiber can be linearly combined based on the volume fraction of each constituent. For example, the longitudinal tensile modulus is the sum of the proportion of each component. The interface in these systems is considered ideal in that it efficiently transmits forces between fiber and matrix without failure. Using this model as a basis for micromechanical analysis and discussion, the magnitude of the forces present at the interface can be predicted. 

T = 140 °C. Here, during solidification, the H increase from 140 °C down to about 100 °C is the result of a double contribution of (a) the crystallization of the fraction of molten crystals and (b) the thermal contraction of the nonpolar phase crystals. The hysteresis behavior is also found in other mechanical properties (dynamic modulus) derived from micromechanical spectroscopy [66, 67], where it is shown that the hysteresis cycle shifts to lower temperatures if the samples are irradiated with electrons. It has also been pointed out that the samples remain in the paraelectric phase, when cooling, if the irradiation dose is larger than 100 Mrad. 

Some analytic expressions are collected in Table 7.6 that have been used in literature to describe the experimental accumulation kinetics, n(t), or dn/dt, the rate of concentration accumulation. Experimentally such kinetics have been studied, both in the alkali-halide crystals [13, 17] and in many metals [43-45] in a wide temperature interval, starting with low (liquid-helium, 4 K) temperatures. Since often a succesful approximation of the accumulation curve is associated with better understanding of a micromechanism of defect formation (see, e.g., [40]) and with other important physical conclu-... 

Therefore, often main attention in studying chemical oscillations is paid to their formal description on the macroscopic level rather than to an attempt to understand in detail the micromechanism of oscillations. It often results in necessity to make a choice between several alternative models suggested for a particular chemical system. It is difficult to restrict ourselves in theory to a definite universal basic model since it can turn out to be either too complicated for studying a particular kind of the autowave processes or, on the other hand, of a limited use due to its inability to reproduce all types of auto-wave processes. 

Other valuable extensions of contact-mode SFM probe micromechanical properties of the sample. Variation of the repulsive force or upward deflection of the cantilever are registered while a Z-modulation is applied either to the sample or the cantilever base (Fig. 6). The dZ/dZc signal contains information about the local stiffness dF/d.8 of the sample, where S=Zt-Zc is the indentation depth. Micromechanical applications will be discussed in Sect. 2.2. 

---