Chapters authored
Measurement and Numerical Modeling of Mechanical Properties of Polyurethane Foams
This chapter focuses on determination of mechanical properties of polyurethane foams applied in automotive industry and medicine. These materials have strong nonlinear viscoelastic behavior that is time dependent. A comprehensive description of their characteristics is very tough and difficult. Mechanical properties can to some extent be studied using mathematical models that need to be verified with measurements. This chapter describes selected mathematical relationships, rheological models, and also numerical simulations that can approximately describe mechanical properties. Mechanical properties of polyurethane foam are influenced by internal and external structure, shape and size of the cells, filling volume, and properties of the used polymer. Studied mechanical properties are contact pressures, stress distribution, and the dependence of stress on the strain rate.
Part of the book: Aspects of Polyurethanes
FEM Analysis of Mechanical and Structural Properties of Long Fiber-Reinforced Composites
This chapter deals with studies of the mechanical properties of samples from long fiber-reinforced composite structures that would contribute to the optimization of the developed constructions made of them. First, the basic issues of composite structures reinforced with long fibers (carbon or glass) and generally of composites with the specification of parameters that would lead to the optimization of mechanical properties with respect to the theoretical strength are presented. Further, the possibilities and methods of measurements of composite reinforced with carbon and glass fibers are described. This is followed by the introduction of analytical models for the description of the transversal isotropic composite, where these mathematical relations allow the determination of unknown elastic constants and they are also important for the verification of numerical models. Finally, it is comprehensively outlined the problems of creating a numerical model of advanced composite fibrous structure for determining the mechanical properties, both through the description of the continuum, and complex numerical model with a structural configuration enabling approach to allow closer interaction among fibers and matrix. Compared to the averaged values obtained from experimental samples, numerical simulations show a similar trend of stress on strain, with results obtained from simulations.
Part of the book: Finite Element Method