[Zurück]


Diplom- und Master-Arbeiten (eigene und betreute):

J. Valencia Novelle:
"Numerical Simulation of the Mechanical Behavior of Perforated Woven Fabric Laminates";
Betreuer/in(nen): D. H. Pahr; Institut für Leichtbau und Struktur-Biomechanik, TU Wien; Universidade de Vigo, 2011.



Kurzfassung englisch:
Woven fabric laminates are composites usually employed in high performance applications. Aerospace or motorsport industries make use of them due to their high strength-to-weight ratio. The topic of this work are so called acoustic laminates in which holes are drilled into laminates in order to reduce acoustic emissions for example in the blocker doors in jet engines. But such laminates have fulfill structural requirements as well.
Composites mostly aim to substitute metal alloys when operating conditions (temperature, impacts,...) make it possible. However, the knowledge of mechanical properties and behavior of woven fabric composites is not so deep and predictable as for in the case of metals. Up to now, many numerical analysis have studied woven fabric laminates using different methods. They mainly have tried to find the way which obtains results with best agreement with experimental tests. The final goal is to susbtitute this latter as much as possible, thus reducing research costs.
The present work simulates non-perforated and perforated three-layered 2/2-twill weave carbon fiber reinforced laminates. The goal is to obtain their effective stiffness tensors and make strength predictions under different loading cases by studying the influence of the holes as well as of the relative displacement of the layers within the laminate. The results are compared with previous experimental tests in order to highlight the validity of the simulations.
The Finite Element Method is employed to carry out these simulations. A set of periodic boundary conditions is defined on 3D representative volumes of the laminates. Throughout the homogenization it is possible to characterize material properties at macro-scale level using the simulation results at meso-scale level. This is done using periodic microfield approaches and the master nodes concept, which allow us to connect meso and macro scales by basing on energy relations.
The effective stiffness tensors and the strength predictions computed from the simulations values obtain a good agreement with previous experimental tests and other numerical studies. The overall results show that perforations of approx. 12% of the surface laminate reduce stiffness to values around a 70% and strength values to around 50% with respect to the non-perforated laminates. It is also evidenced that relative displacements of the layers do not imply serious variations on the stiffness values but they produce considerable variations on the strength predictions.
The present work is the straight continuation of the work by Dieter H. Pahr in "Experimental and Numerical Investigations of Perforated FRP-laminates" (Fortschritt-Berichte VDI Reihe 18, Nr. 284, Düsseldorf 2003) and by Christof Marte in "Untersuchung von 2/2-Twill-Gewebe Laminaten mit Hilfe von 3D-Finite Elemente Einheitszellen" (Diplomarbeit, ILSB, TU Wien, Vienna 2004), with some differences that have to be point out. In the work of D.H. Pahr, woven fabric laminates were simulated as homogenized material; in contrast to this, here the roving and matrix material are modeled separately in detail and not as homogeneous layer. In the work of C. Marte, only non-perforated laminates were modeled; with respect to this, here holes are added up to the simulated laminates.
The aim with the results is to predict mechanical behavior of perforated carbon fiber laminates, and also to be aware of possible fluctuations on the properties due to manufacturing inaccuracies or unexpected unalignements of the layers.

Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.