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Peter Niemz

Peter Niemz
ETH Zurich | ETH Zürich · Department of Civil, Environmental and Geomatic Engineering

About

525
Publications
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Introduction
Peter Niemz worked at the Department of Civil, Environmental and Geomatic Engineering, ETH Zurich. Peter does research in Materials Engineering. He retired 2015

Publications

Publications (525)
Article
Der Holzbau gewann in den letzten Jahren stark an Bedeutung. Brettschichtholz und Brettsperrholz werden heute im großen Um-fang eingesetzt, insbesondere auch in großen mehrstöckigen Wohn- und Verwaltungsbauten. In der DACH-Region, in Italien und Tschechien wurden 2020 zum ersten Mal knapp über 1 Mio. m³ Brettsperrholz gefertigt (Holzkurier, 2021)....
Article
Full-text available
An approach to mathematical modeling and research on the 2D non-stationary temperature distribution in non-frozen wooden prisms with different thicknesses during their simultaneous autoclave steaming at limited heat power of the steam generator and during the subsequent air conditioning before the cutting of veneer is described in the paper. Mathem...
Article
Full-text available
Although glueing softwood is well mastered by the industry, predicting and controlling bond quality for hardwood is still challenging after years of research. Parameters such as the adhesive type, resin–hardener ratio, and the penetration behaviour of the wood are determinants for the bond quality. The aim of this work was to assess to what extent...
Article
Wood science covers in particular the areas of the formation and composition as well as the chemical, biological and physical-mechanical properties of wood. First comprehensive studies have already been published in the last century. Detailed knowledge of wood is required for the processing of wood, the production of wood-based materials, and the u...
Article
The feasibility of a portable NIR sensor for off-line determination of diverse wood quality aspects relevant in the production of glue-laminated timber was demonstrated. The best performance was noticed for assessing wood moisture content, with a lower capacity to estimate wood density and mechanical properties. NIR spectroscopy was modestly capabl...
Article
Full-text available
In recent decades, coniferous façade boards from untreated wood have been used extensively without the use of biocides, flame retardants and weather protection coating systems. This work is focused on testing selected properties of 4 untreated softwoods-spruce, larch, pine and Douglas fir-exposed outdoors for 3, 6, 12 and 24 months during direct fl...
Article
Full-text available
Es werden methoden zur zerstötungsfreine Prüfung von Holz Zusammengestellt (Review Papaer). Schallausbreitung,Eigenfrewuenz,Thermographie, optische Verfahren, Durchstrahlung
Article
Full-text available
This paper describes a methodology for mathematical modeling, computing, and research of two mutually connected problems: 2D non-stationary temperature distribution in logs stored for a long time in an open warehouse at periodically changing ambient air temperature in winter and change in the icing degrees of the logs during this time. Mathematical...
Conference Paper
Full-text available
Oriented investigations on the application of NIR spectroscopy for the evaluation of the bonding quality of glued laminated timber Peter Niemz1) Jakub Sandak2), Juana Mai3), and Andreas Hänsel3) 1) ETH Zürich, Stefano-Franscini –Platz 3, CH 8093 Zürich and University in Skelleftea/Sweden 2) InnoRenew CoE, Livade 6, 6310 Izola, Slovenia and Univers...
Article
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Various factors affect the bonding quality of elements used for timber construction. This review includes literature studies and personal experiences related to relevant technological variables defining glue bond performance in glue-laminated timber elements during their service life. The gluing of hardwood species receives special focus as it is c...
Article
Full-text available
An approach to computing and research on the 2D non-stationary temperature distribution in horizontally situated logs in an open warehouse under the influence of periodically changing atmospheric temperature in winter and during their subsequent steaming in autoclaves is described in the paper. Mathematical descriptions of the changing atmospheric...
Article
Full-text available
Wood-based composites hold the promise of sustainable construction. Understanding the influence on wood cellular microstructure in the macroscopic mechanical behavior is key for engineering high-performance composites. In this work, we report a novel Individual Cell Tracking (ICT) approach for in-situ quantification of nanometer-scale deformations...
Article
Full-text available
This article presents an approach for computing the 2D temperature field, average mass temperature, and relative icing degree of logs subjected to many days and nights of continuous alternating freezing and thawing at periodically changing air temperature near them in winter. Mathematical descriptions of the periodically changing atmospheric temper...
Article
Full-text available
The accuracy and reliability of a measuring device is crucial to determine the quality of wood surface. This paper compares the surface quality of thermally modified spruce wood measured by two different methods. Spruce wood specimens were thermally modified at different temperatures (160, 180, and 210°C) and then milled with a single-spindle milli...
Article
Full-text available
Subject to this study is the modification of an experimental two-component polyurethane (2C PUR) as an alternative adhesive for structural hardwood bonding. The 2C PUR has been adapted by calcium carbonate as filler to increase its modulus of elasticity with the aim of increasing the modulus analogue to the ones typically observed for classic amino...
Article
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The effect of short-term thermomechanical (STTM) densification on shear strength of plywood produced with Scots pine (Pinus sylvestris L.) veneers was investigated. The veneer sheets were densified under temperatures of 20 °C, 120 °C, and 180 °C, and pressure of 1 MPa for 2 min. There were four polyvinyl acetate (PVAc) adhesives, 1 emulsion polymer...
Article
Full-text available
The purpose of this study was to analyze the effect of thermal treatment on chemical changes, mechanical properties and machining behavior of African padauk wood. Thermal modification of padauk wood was carried out at 3 different temperatures (160 °C, 180 °C, and 210 °C). Effect of modification temperature on chemical constituents and bending prope...
Article
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The performance of adhesive-hardwood bonds can often be sensitive to humidity and temperature variation. Therefore, it is frequently challenging to achieve standard requirements for structural applications. To gain a better understanding of the wood-adhesive bond, the properties of the individual constituents as well as the local interface of Europ...
Article
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The feasibility of using the modified Hartman–Schijve (HS) equation to analyze the fatigue fracture performance of adhesively bonded wood specimens under cyclic mode II loading was investigated in comparison with the Paris crack growth equation. Wood joints prepared with three different adhesives have been subject to cyclic Mode II testing at room-...
Article
Aufgrund veränderter waldbaulicher Konzepte wird in der Schweiz, Deutschland und Österreich mehr Laubholz angebaut. Die Nutzung dieses Holzes erfolgt derzeit überwiegend energetisch. Buche und auch Esche werden aber auch verstärkt im Bauwesen als Brettschichtholz (BSH) oder als Verstärkungen im Verbindungsbereich eingesetzt. Problematisch ist der i...
Article
It is generally assumed that the properties of wood against fatigue are good, but little is known about the properties of adhesively bonded wood, which represents today most of the wood-based products. Lap-shear samples glued with three common wood adhesives [two ductile one-component polyurethane (1C-PUR) systems and one brittle phenol resorcinol...
Article
Full-text available
The use of a fracture mechanics approach for design of engineering structures is relatively rare compared to stress or stiffness based approach. Using a fracture mechanics approach, the influence of defects and their propagation can be better described than using a stress or stiffness approach. Also, stress or stiffness approaches are generally con...
Article
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In this paper, acoustic emission (AE) signals obtained during quasi-static crack propagation in adhesively bonded beech wood were classified using an unsupervised pattern recognition method. Two ductile one-component polyurethane (1C-PUR) adhesives with the same formulation except for one system being reinforced with short polyamide (~ 1 mm long) f...
Article
A new numerical model for wood-adhesive joints, which allows an efficient hygro-mechanical analysis of a glued joint by means of the finite element method, is proposed. A cohesive element model is modified by adding features to simulate the mechanical behaviour of and the moisture transport in the joint. The numerical investigations of two wood spe...
Presentation
Full-text available
Moisture induced strain and delaminanation in glued wood under dry conditions in heated building (problemens, open investigations)
Article
In this paper, the frequency dependent energy dissipation of typical wood adhesive under cyclic stress was studied on film adhesive samples. Three moisture-curing one component polyurethane (1C-PUR) adhesives with relative ductile behavior, one melamine formaldehyde (MF) and one phenol formaldehyde resorcinol (PRF) adhesives both with a more brittl...
Conference Paper
Full-text available
Fracture-mechanical bending tests on glued wood test specimens under quasi-static and cyclic loading were monitored with resonant acoustic emission sensors. The purpose of the acoustic emission analysis was, besides visual observation and evaluation of compliance, to use another independent criterion for crack initiation and crack propagation. In a...
Article
Bonding of hardwood for structural applications is a complex process. Various factors influence the bond performance and the interface area is considered the most crucial part. The chemical composition of the interface, e.g. wood extractives, is expected to influence the bonding of hardwoods. The subject of this study was to determine the influence...
Article
This paper investigates the energy release rate (ERR) in Mode II in-plane shear during delamination propagation under quasi-static and cyclic fatigue fracture loading with the 4-point end notched flexure (4-ENF) fracture test specimen. Wood joints bonded with three different adhesives, one rather brittle phenol resorcinol formaldehyde (PRF) and two...
Article
Es wird über die Verklebung von Eschenholz mit 1 K PUR Klebstoffen und Primern mit Tensiden berichtet.Zum Vergleich wird PRF getestet. Nach Primern erfüllen ausgewählte PUR Klebstoffe die Normvorgaben für den Delaminierungstest nach EN 302-2. Die Verklebung erfolgte unter industriellen Bedingungen.
Conference Paper
Adhesive bonding is becoming more and more important for manufacturing structures or structural elements made from wood. For designing such structures, the performance of adhesives has to be evaluated under quasi-static and cyclic fatigue loading as well as under corresponding fracture loads. The performance of wood glued beams under quasi-static l...
Article
In Teilbereichen des schweizerischen Jura kommen in der Region um La Brévine Fichtenbäume vor, die nach entsprechender Auswahl hinsichtlich Standort, Stammform und auch Eigenschaften durchaus für den Einsatz als hochwertiges Klangholzsortiment geeignet sind. Jahrringlage, Dichte und akustische Eigenschaften entsprechen denen von Klangholz aus ander...
Article
The increasing quantity of hardwood growing in the Swiss forest represents an opportunity for the future of the wood industry. Glued laminated timbers made of hardwood offer higher strength and stiffness properties than the softwood equivalents, and they are often used in combination with softwood for local reinforcement. Additionally, their visual...
Article
Full-text available
Wood with distinctively different properties in the longitudinal, radial and tangential directions exhibits a strong moisture-dependent material characteristic in the elastic range. The purpose of this study was to analyze the orthotropic elastic properties of Chinese fir wood [Cunninghamia lanceolata (Lamb.) Hook] determined at different moisture...
Article
In this work, we model ACU transmission in delaminations, with focus in the interference effects resulting from multiple ultrasonic reflections within the delamination layers and the resulting changes in the amplitude and time of flight. For this purpose, we propose a simplified analytical model, which we cross-validate with full-wave finite-differ...
Article
In this study, several theoretical models to numerically estimate shear properties of orthotropic materials are introduced. These approaches are based on the combination of Hankinson’s empirically derived formula with other empirical and analytical calculations. Next to shear moduli, which are estimated from the elastic moduli and Poisson’s ratios,...
Article
When bonding wood for structural applications, the wood-adhesive-bond is influenced by a variety of factors. Next to the physical and mechanical properties of wood species, their chemical composition e.g. wood extractives can play a role in bonding wooden surfaces. A two-component polyurethane system (2C PUR) was chosen to better adapt to the curre...
Article
Full-text available
Elastic and strength properties are very important material characteristics in mechanical modelling. Due to the anisotropic and hygroscopic nature of wood, a characterization of wood mechanical behavior will require knowledge of its moisture-dependent properties in relation to the three principal axes of anisotropy. The influence of moisture conten...
Article
Full-text available
The diffusion properties of walnut (Juglans regia L.) and cherry (Prunus avium L.) wood perpendicular to the grain are presented. The wet and dry cup tests were carried out in normal climate conditions. Simultaneously, inverse analyses by means of the finite element (FE) method were conducted based on the experimental sorption data. The results sho...
Article
Zur Orthotropie der physikalisch- mechanischen Eigenschaften von Fichtenholz. Fichte und Kiefer sind die im Bauwesen am häufigsten eingesetzten Holzarten. Insbesondere Brettschichtholz, Brettsperrholz oder Brettstapelelemente werden oft aus Fichte hergestellt. Zudem dient Fichte häufig als Trägermaterial für Mehrschichtparkett. Für FE-Berechnungen...