Papers by Author: Daisy Weber

Abstract: Conventional mechanical and structural properties allow to describe the complete composite material. They do, however, not describe the reaction during the pyrolysis process. The dynamic mechanical thermal analysis (DMTA) is a technique which is used to characterize materials. In particular, the DMTA method is used to observe the viscoelastic nature of polymers. Another interesting application area of the DMTA is the simulation of pyrolysis experiments to obtain carbon/carbon composites (C/C composites). The pyrolysis process of carbon-fibre-reinforced plastics (CFRP) was performed by means of inert gas (Ar, ambient pressure) under a defined time-temperature profile or alternatively approached by short time sweeps in a DMTA. So the temperature dependence of the elastic modulus (E-modulus) and of the internal damping (tan δ) are determined starting from the cured carbon-fibre-reinforced plastic to the transformed C/C composites. The analyses were applied for different matrix resins. The shown method improves the access to usually hidden mechanical and structural properties and requires further investigation of the entire polymerization and pyrolysis processes.

Abstract: Most composite components are constructed in a very safe way, with thick walls and many laminate layers. The potential of lightweight construction will not be fully tapped. In a typical computation of the behavior of a component, the wall thickness and fiber directions have to be entered into the simulation system. The result is the load-dependent deformation of the component. That approach takes a lot of time to get an optimized construction. A better way for optimizing fiber-reinforced composites is the use of simulation algorithms to get an optimal material distribution. In this case, the simulation output shows the optimal layer thickness and fiber directions for every node depending on the selected maximum deformations and the load of the structure. This method was used to reduce the weight of the special, extremely energy-saving vehicle called “Sax 3” of the student project “fortis saxonia” for the Shell Eco-marathon 2008. Thus it has become possible to keep the weight of the chassis of the vehicle under 10 kg. This shows the high potential of the implementation of this optimization approach for fiber-reinforced composites.