Domain superposition technique

Jiang W-G, HaUett SR, Wisnom M. Development of domain superposition technique for the modehng of woven fabric composites. In Camanho PP, editor. Mechanical response of composites. Dordrecht, The Netherlands Springer 2008. 

The mesh superposition technique[6] is used to simphfy the mesh generation of the flow domain(see Fig.l). The elements used were hexahedron elements with 8 nodal points in each element. Material(PE) properties used in the simulation are as follows ... 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

FT NMR excite all nuclei of a given species simultaneously. Therefore, the FID is a complex interferogram consisting of the superposition of a number of damped oscillations with resonance frequency and relaxation time characteristic of each chemically distinct nuclear environment. Fourier transformation separates the components in the frequency domain. The same chemical shift information is obtained as in CW NMR but in a timescale of seconds rather than minutes. FT NMR is therefore a much more efficient method for the application of time-averaging techniques. 

The examples presented below employ linear system identification techniques in which superposition and scaling are assumed. These enable conversion between the frequency and time-domain models. Nonlinearities in conducting polymers can arise from significant potential-dependent ionic and electronic conductivities, for example. In cases where nonlinearities are significant, it may nevertheless be appropriate to apply linear techniques over certain ranges of voltage, strain, or charge state where response is effectively linear. 

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