Multiphase layout optimization for fiber reinforced composites applying a damage formulation: Fid-Bau Portal

Multiphase layout optimization for fiber reinforced composites applying a damage formulation

Kato, Junji / Ramm, Ekkehard

The present study addresses an optimization strategy for maximizing the structural ductility of Fiber Reinforced Concrete (FRC) with long textile fibers. Due to material brittleness of both concrete and fiber in addition to complex interfacial behavior between above constituents the structural response of FRC is highly nonlinear. Consideration of this material nonlinearity including interface is mandatory to deal with this kind of composite. In the present contribution three kinds of optimization strategies based on a damage formulation are described. The performance of the proposed method is demonstrated by a series of numerical examples; it is verified that the ductility can be substantially improved. Conclusion : Multiphase material optimization, shape optimization of fiber geometry and the combination of both methodologies, namely 'multiphase layout optimization' were applied for maximizing the structural ductility of textile fiber reinforced composites. The two brittle materials, namely concrete matrix and fibers, get the necessary ductility from the interface behavior of the two constituents. For this objective, it is of course not sufficient to base the optimization process on a linear material model so that it is mandatory to consider material nonlinearities in the optimization process. It was verified in the numerical example of multiphase material optimization that the threephase composite using an AR-glass and carbon could optimally improve the ductility of FRC. However in this first approach fiber materials are defined only in prescribed design elements, and only straight fibers are allowed. As a remedy first shape optimization of fiber geometry was developed. It could be shown that the ductility of FRC could be substantially increased with respect to the geometrical layout of continuous fibers. However it was also recognized that some fibers could be exploited in more optimal way from viewpoint of structural engineering. In order to obtain more efficient designs multiphase layout optimization was developed. This concept of both above mentioned schemes was discussed in the context with numerical examples, by these simulations the ductility of FRC could be further improved utilizing the advantages of both multiphase material and shape optimization. This methodology is suited to the optimization of other fiber reinforced composites.