Boyd composite model

Boyd [13] has analysed the d3mamic mechanical behaviour of PET in terms of a composite model of crystalline and amorphous phases. The relaxation strengths for the a and P processes, determined from the shear modulus results of Illers and Breuer, were shown to be related to the crystallinity, indicating that both relaxation processes related to the amorphous regions. For the P processes, the shear modulus for the amorphous phase lies between the upper (Voigt) and lower (Reuss) bounds in both the relaxed and unrelaxed states. The a process, however, appeared to fit best near the lower bound behaviour. 

The U.S. Navy has sponsored research at Virginia Tech to look at structural performance of FRP for the previously mentioned deck applications. This included work on determining the postftre structural properties. This work was reported in detail in the doctorate dissertation of Steven Boyd in 1996.27 Gibson et al.28 did work on modeling the residual mechanical properties of composites after fire. There have been recent studies on the mechanical properties of composites after fire,29-31 some of which have been cited previously in this chapter.1314 The requirements for the Navy applications have been described by Sorathia.19 20 32... 

Sipe, J.E., Boyd, R.W. Nonlinear susceptibility of composite optical materials in the Maxwell Garnett model. Phys. Rev. A 43, 1614-1629 (1992)... 

The above-mentioned thermomechanical models only consider the elastic behavior of materials. Boyd et al. [13] reported on compression creep rapture tests performed on unidirectional laminates of E-glass/vinylester composites subjected to a combined compressive load and one-sided heating. Models were developed to describe the thermoviscoelasticity of the material as a function of time and temperature. In their work, the temperature-dependent mechanical properties were determined by fitting the Ramberg-Osgood equations and the temperature profiles were estimated by a transient 2D thermal analysis in ANSYS 9.0. 

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