Rheology for processing

The core competence of the Materials Technology group (MATE) is formed by the triangle of numericalmethods, constitutive equations and experimental methods. The ultimate goal of the group is to bridgethe gap between science and technology in the area of materials processing and design, via the useof computational tools in the modelling of the full thermo-mechanical history of material (elements)during their formation, processing and nal design, in order to be able to quantitatively predict productproperties.This approach will be demonstrated with some illustrative examples of research projects. The rstexample is the (extended) POMPOM model for describing viscoelastic ows of polymer melts. Thisnew model shows excellent predictive capability and is considered to be a break through in the area ofviscoelastic modelling. The results of viscoelstic modelling are an important part of other issues like owinstabilities (example 2) and ow induced crystalization of semi-crystaline polymers (example 3). Thelast two examples are applied to injection moulding. Finally, the modeliing of mixing is dealed elds. A new tool, the so-calledmapping method, is demonstrated, This method allows, for the rst time, optimization of highly viscousmixing processes with a constant rheology

Flow-induced crystallization and resulting anisotropic properties

It is well known that flow gradients can have a major influence on the crystallization of semi-crystalline polymers. Not only the nucleation rate can change dramatically, but also the type of nuclei can change depending on the level of orientation of the molecules; especially the orientation the high molecular weight fraction. The level of modeling of flow induced crystallization (FIC) has improved quite a lot the last few years. Even the influence of hard particles on the local stress level and the FIC behavior is now studied numerically. These models reveal the importance of the coupling between rheology and FIC. Having available reliable parameters values that enter these models is becoming more urgent and so is the need for reliable and accessible experiments that combine rheological characterization methods with structure characterization methods. We use shear and extensional flow combined with different structure characterization methods such as microscopy, TEM and SEM, SALS, FIB and WAXS/SAXS on both linear and a branched polymers. The evolution of the detailed structural information, including crystallinity, lamellae thickness, long spacing, spherulite size and orientation, is linked to the evolution of the rheological parameters and providing, in this way, the input for the models. Next, we link this structural information to mechanical properties, in particular the impact strength.A full multi scale approach is used that allows for taking into account anisotropy at different levels and the influence of both soft and hard particles

Mechanical modeling of skin

\u3cp\u3eThe chapter describes the work that was performed in the soft tissue biomechanics laboratory at Eindhoven University of Technology on the biomechanics of skin. A rationale is given for the changes from standard testing methods to inverse methods, from in vitro to in vivo and back to in vitro testing and for the more detailed studies on individual skin layers of the last decade. The chapter tries to explain how our vision on testing methods and modeling changed over the years and why the pursuit towards a complete constitutive model is still ongoing.\u3c/p\u3

Mandrel for making stented or stentless heart valve comprising a fibre reinforced composite material

he mandrel comprises a cylindrical lower mandrel half-section with at least three sloping surfaces at its top end, and a cylindrical upper mandrel half-section containing a cavity with sloping side walls in its bottom end, the angles of these side walls corresponding to the angles of the sloping surfaces at the top end of the lower mandrel half-section. The bottom end of the upper mandrel half-section is provided with protuberances extending in the circumferential direction, the number and positions of which correspond to the cavity side walls. A mandrel used for making a synthetic, fibre-reinforced heart valve comprises an essentially cylindrical lower mandrel half-section with at least three sloping surfaces at its top end, and an essentially cylindrical upper mandrel half-section containing a cavity with sloping side walls in its bottom end, the angles of these side walls corresponding to the angles of the sloping surfaces at the top end of the lower mandrel half-section. The bottom end of the upper mandrel half-section is provided with protuberances extending in the circumferential direction, the number and positions of which correspond to the cavity side walls. Independent claims are also included for (a) two methods for making a synthetic, fibre-reinforced stentless heart valve using this mandrel, (b) a method for making a synthetic, fibre-reinforced stented heart valve using this mandrel, and (c) a synthetic, fibre-reinforced stentless heart valve comprising an essentially cylindrical tube with outwards protruding parts and leaflets on the inner wall, the leaflets containing reinforcing fibres (42) that extend into the tube material