From Aero Engines of the future it is demanded to provide more power, while the fuel consumption and the mass should decrease. In order to reach the goal of an increasing specific power or a decreasing specific mass, respectively, structural optimization methods, like the topology optimization, find their way into the design process to a greater extent. Additionally one is going to consider more and more fiber reinforced composites as a substitute for titanium alloys in the “cold” structure of the engine. Composite materials offer significant advantages especially concerning the specific mass and the adjustability of their stiffness properties. Unfortunately it is very difficult to predict damage and fracture of such orthotropic materials. The presentation will show the results of a topology optimization of the titanium intermediate-casing of a Rolls-Royce aero engine. Further on the material of the casing will be substituted by a carbon fiber reinforced composite. The fiber orientations and layer thicknesses of the composite are optimized under certain strength constraints, which are described by a modern fracture plane based failure criterion (NASA LaRC04 criterion [6]). Such a failure criterion has a lot of advantages compared to classical ones like Tsai-Hill, Tsai-Wu, ..., which e.g. do not distinguish between fiber and inter-fiber fracture and are therefore not able to predict the type of inter-fiber fracture. Finally the results of the optimization with the current material titanium will be compared to the results of the composite-made intermediate casing in terms of their load capacity and weight.
Fracture Mechanism and Acoustic Emission of Unidirectional Flawed Materials with Carbon Fiber Reinforced Nylon 6.