Production problems attributed to excessive stresses generated during the cure of epoxies led us to develop a formalism to predict these stresses. In our first studies, we developed a fundamental understanding of the complex evolution of viscoelasticity as the cure progresses. We then incorporated these results into a proper tensorial constitutive equation that was integrated into our finite element codes and validated using more complicated geometries, thermal histories, and strain profiles. The formalism was then applied to the original production problem to determine cure schedules that would minimize stress generation during cure. During the pursuit of these activities, several interesting and puzzling phenomena were discovered that have stimulated further investigation.
A detailed analysis of energy inputs and outputs is performed on grain-based gasohol (10 percent grain-based ethanol, 90 percent gasoline). Existing differences of opinion on the energy balance derive mainly from variations in interpretation which are several examples of inherent methodological problems in energy analysis. The result is strongly dependent on assumptions about use of crop residues for fuel and the miles-per-gallon rating of gasohol. In terms of total nonrenewable energy, gasohol is close to the energy break-even point. On the other hand, in terms of petroleum or petroleum-substitutable energy, gasohol is an unambiguous energy producer, since most energy inputs to the process can be supplied by nonpetroleum sources such as coal.
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