Die Holzforschung München der Technischen Universität München bietet eine Abschlussarbeit zum oben genannten Thema an.

Hintergrund

In einem aktuellen Forschungsprojekt an der Holzforschung München werden weitspannende Holz-Stahl-Hybridelemente für die Anwendung als biegebeanspruchte Deckenelemente entwickelt. Die Elemente bestehen aus einem Stahltrapezblech-Kern, der beidseitig mit Furnierschichtholz beplankt ist. Vor allem in den Auflagerbereichen können hohe Druckkräfte quer zur Plattenebene wirken, die u.a. zu einem Beulen des Stahltrapezblechs als ausschlaggebenden Versagensmechanismus führen können. In der ausgeschriebenen Masterarbeit soll im Zuge einer experimentellen Parameterstudie das Querdruckverhalten der Hybridelemente untersucht werden.

Aufgabenstellung

• Umfassende Literaturstudie zum Querdruckverhalten von Furnierschichtholz sowie zum Tragverhalten von Stahltrapezblechen
• Herstellung der Prüfkörper und Einrichten des Prüfstands
• Planung und Durchführung von Experimenten zur Ermittlung von Tragfähigkeiten und Steifigkeiten des Holz-Stahl-Holz-Gesamtsystems unter Querdruckbeanspruchung
• Statistische Analyse der Versuchsdaten und Entwicklung von Berechnungsmodellen zur Beschreibung des Trag- und Verformungsverhaltens
• Abgleich der experimentellen Ergebnisse mit Modelldaten der FE-Analyse

Anforderungen

Sehr hohe Einsatzbereitschaft und Teamfähigkeit, Kreativität, gutes mechanisches und materialtechnologisches Verständnis, Kenntnisse in statistischer Datenanalyse, handwerkliches Geschick.

Termin

Nach Vereinbarung.

Kontakt

Maximilian Westermayr: westermayr(at)hfm.tum.de

Wood Technology department of the Technical University of Munich is providing the named subject in the form of a master thesis.

Description

Wood is a bio-material with anisotropic and non-homogenous material properties. Damage in wood can happen due to several reasons, including the drying effects, and accumulation of the stresses on the location of joints. Due to orthotropy of this material, different damage parameters should be considered for wood to cover failure of this material both under tension as well as under compression. Damage of wood is ductile under compression and brittle or quasi-brittle under tension and shear. The purpose of this thesis is to enhance failure modes for damage initiation. Different criteria need to be taken into consideration, implemented as user-defined material models in the computational software Abaqus to be investigated on specific benchmark problems.

The following points should be satisfied during the thesis:

• Literature review on different failure criteria for damage initiation in the composite materials and wood
• Implementation and further developement of user-defined material models (UMATs) in Abaqus
• Investigation of UMATs on benchmark problems

• Damage propagation

Language: English, Thesis available from September 2021

Supervision and further information: Franziska Seeber, Ani Khaloian, Prof. van de Kuilen

Wood Technology department of the Technical University of Munich is providing the named subject in the form of a master thesis.Wood Technology department of the Technical University of Munich is providing the named subject in the form of a master thesis.

Description

Glued laminated timber is a type of structural engineered wood product or a wooden composite comprising a number of layers of dimensioned lumber bonded together with durable adhesives. This product can be provided in different dimensions and shapes for different applications. Nowadays, curved wooden glulams are being used under varrying environmental conditions. The main purpose of this thesis is to analyse the moisture movement and consequently the residual stresses developed between the layers during manufacturing and service life, considering the influences including adhesive properties, fiber deviations, beam curvatures, etc. By developing an orthotropic viscoelastic mechano-sorptive material model, the influence of the residual stress on the long-term behavior of the structures shall be studied.

The following points should be satisfied during the thesis:

• Literature work to find out moisture-related properties of adhesives and wood
• Further developing the orthotropic viscoelastic mechano-sorptive material model using UMAT of ABAQUS
• FE simulation of moisture transfer in composite member  and coupled moisture-stress analysis

• Parametric study on geometrical and material varriation

Language: English

Supervision: Taoyi Yu, Ani Khaloian

Beech (fagus sylvatica) stock in German forests is increasing [1] while the use of beech wood for construction purposes is not popular yet. Beech glued laminated timber offers high compression strength and stiffness which makes it favourable to be used in load bearing columns. Beside possible material failure due to increase in stresses, these columns may face stability issues, such as buckling as well.

Buckling behaviour of columns can be studied and be modelled by means of Finite Element method. Finite element models, in general need to be validated for their extended use in application. Experimental testing of the buckling behaviour of beech glulam columns has been performed at Holzforschung München without considering structural imperfections in single layers [2]. However, the dynamic material properties of the applied lamellas in the beech glulam are available. Dynamic properties of these lamellas exhibit a correlation with strength and stiffness properties [3]. It was also shown that material heterogeneities and imperfections are influencing the strength properties of beech lamellas. Therefore, after studying the influence of these lamella imperfections on stability of the glulam and by further developing the method for modelling of buckling, setups need to be suggested for glulam beams based on the available dynamic properties of single lamellas in this thesis. In the end, some experimental testing on beech glulam columns will be performed where dynamic properties as well as locations and sizes of the knots in the single layers are known.

Tasks of the thesis are:

• Studying of orthotropic and heterogeneous behaviour of wood and its influence on stability problems.
• Suggesting setups for beech glulam, based on the available strength and stiffness properties of single lamellas from tension tests.
• Further developing the provided approach for simulation of buckling behaviour.
• Performing small set of experiments on beech glulam columns (where the information about imperfections in single lamellas are known) for validation of the model.

Required knowledge:

• Background in modelling and simulations

Date: WS 20/21

Supervisor: Franziska Seeber, Ani Khaloian Sarnaghi

[1]     Federal Ministry of Food and Agriculture (2015): The forests in Germany. Selected results of the third national forest inventory.

[2]     Zeilhofer, M. (2019): Mechanical behaviour of beech glued laminated timber columns subjected to compression loading. Master’s Thesis, Holzforschung München.

[3]     Westermayr, M.; Stapel, P.; van de Kuilen, J.W. (2018): Tensile strength and stiffness of low quality beech (Fagus sylvatica) sawn timber. WCTE.