Peter Niemz

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

Beech wood, renowned for its diverse applications spanning construction, flooring, furniture, veneer, and plywood, holds a paramount position among industrial wood species. Nevertheless, the myriad of beech species worldwide, coupled with the dynamic impact of climate change, have produced structural variations within beech trees. Extensive researc...

This study aimed to investigate the combined effect of steaming and heating on the equilibrium moisture content (EMC) of Turkey oak (Quercus cerris L.) wood over a nine-year period. The study also aimed to determine the impact of steaming on water absorption and water permeability, crucial for the durability of the species against environmental fac...

A short overview about the creep from wood and wood based panels is preented. State of the art and also open questions like Kdef values for particleboards and selected other wood based materials. In fluence from adhesives, particles , structure from wood and wood based materials, moisture content.Overview about selected running works world wide

The presentation present a short overview about the development of wood research. A overview about important reseachrers, institutes and conountries will be presented. lso the change in the used languages Franch German now English and the number of publications for different timetables are given

The temperature resistance of glued timber, which is crucial for glued wood construction, represents a significant assessment criterion. To gain insights into this aspect, this study utilized methods such as a shear strength test in accordance with EN 302-1:2013-06 under thermal loading (from 20 °C to 200 °C), and Differential Scanning Calorimetry...

Cross-laminated timber (CLT) CLT is an excellent material for building and high load-bearing structural applications, but its fabrication and use are limited to softwood only. The suitability of aspen (Populus tremula L) wood for manufacturing CLT was assessed by using two adhesives, one-component polyurethane (1C-PUR) and melamine adhesive (ME). P...

The single exponential kinetics (SEK) and parallel exponential kinetics (PEK) models were fitted to kinetic sorption data of welded and unwelded Scots pine ( Pinus sylvestris L.) and European beech ( Fagus sylvatica L.). Furthermore, diffusion coefficients of water vapour in wood were determined using two different Fickian diffusion solutions. The...

The use of wood in construction requires knowledge of the mechanical properties and the particularities that wood presents in comparison with other materials used for structural purposes such as steel, concrete, brick, or stone. The introduction mentions the environmental advantages that justify the use of wood today. The orthotropy of wood is one...

The wood–water interactions of welded bond-lines of European beech ( Fagus sylvatica L.) and Scots pine ( Pinus sylvestris L.) were in this paper studied for the first time with dynamic vapour sorption equipment. The aim of this study was to characterize the water sorption in the welded bond-line and to define to which extent it deviates from water...

The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method. This paper investigates the influence of CO 2 laser cutting on the wetting properties, the modified chemical component of the laser-cut surface, and the strength and adhesive penetration near the bondline. Beech-wood is cut by the l...

This chapter is an Appendix that provides information on material and process parameters. The data may constitute a basis for a first approximation in calculations of material characteristics and production capacities, etc. The presentation is in tabular form, sometimes with indications of the variation range. Data are presented for solid wood of d...

This chapter deals with the fire properties and performance of wood products and structures. It starts with two subchapters on the basic physical and chemical properties under fire conditions including fire-retardant treatments to obtain higher reaction to fire classes. A new European standard to evaluate their long-term fire performance is include...

The variety of wood-based products is huge; some are produced and marketed in large volumes while others are for a very specific use and therefore also often only produced in small volumes. This chapter introduces a group of new materials, existing mainly only in laboratories or in production at pilot scale. These materials often go under the name...

Knowledge of the strength of wood and wood-based materials is an important basis for the calculation and dimensioning of wooden products. This chapter describes the basics of the strength properties, test methods, important influencing parameters (e.g., moisture content, load direction, type of load, duration of load, speed of loading). Phenomenolo...

Knowledge of the elastic and inelastic properties of wood and wood-based materials is an important basis for the calculation of deformations of wood under external loads and also for the deformations and stresses caused by moisture changes (e.g., stresses in wood during drying, deformation of wood elements in different climates). Wood is an orthotr...

This chapter describes the basic physical properties of wood and wood-based materials such as density, thermal properties, electrical properties, friction, optical properties, corrosion, and aging. In addition, selected new innovative testing methods are presented, which are still mainly used in research.Together with the very high influence of (i)...

Wood science covers in particular the areas of the formation and composition as well as the biological, chemical, and physical–mechanical properties of wood. The first comprehensive studies were published in the last century (for example, Franz Kollmann [wood science and technology], Christen Skaar, John F. Siau [wood and moisture relations], Boris...

A methodology for the computation of the thermal energy efficiency of modes for the heat treatment of frozen wooden prisms in an autoclave with saturated water vapor at changing operational conditions has been proposed. The methodology includes computer simulations with two own-coupled unsteady models: one to calculate the 2D temperature distributi...

The mechanical properties of cured wood adhesive films were tested in a dry state by means of nanoindentation. These studies have found that the application of adhesives have an effect on the accuracy of the hardness and elastic modulus determination. The highest values of hardness among the tested adhesives at 20 °C have condensation resins: MF (0...

This study aimed to characterize the surface quality of beech wood (Fagus sylvatica L.) cut by a CO2-laser. Boards were conditioned to a low (about 8% moisture content), 12%, and a high, (about 18%) moisture content. Laser cutting was performed at varying processing parameters, i.e. cutting speed, gas pressure and focal-point position. A confocal m...

An approach for calculation of the duration of regimes for intensive autoclave steaming of frozen wooden prisms in cases of dispatching interferences into the operating temperatures has been suggested. The approach is based on the use of two coupled personal mathematical models: a 2D non-linear model of the unsteady distribution of the temperature...

The sorption isotherms during adsorption and desorption of 25 wood species from Cameroon (included 3 species from plantation in Togo) were determined. In addition, the chemical compositions of these wood species were tested. The equilibrium moisture contents in a normal climate varied between 10,55% and 15,6%. A clear influence of the proportion of...

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)....

Particleboard is an important base-material in furniture and building applications and its annual production capacity worldwide is over 100 million m³. Wood is the main raw material used, although the feasibility of non-wood alternatives exists. This technical note summarises information about how wood-particle geometry affects the bulk density and...

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...

This paper describes an approach for computing the specific heat capacities of logs stored for long in an open warehouse. It includes the heat capacities of the wood of non-frozen and frozen zones in the logs and of both the frozen free and bound water in these zones, also the capacities formed by the release of the latent heat of both the free and...

The hygroscopic nature of wood leads to large moisture fluctuations in the material that may influence the mechanical performance of glued wood products. Adhesives based on bone, fish and hide have a long tradition for the gluing of wood and can be found in wooden structures in our cultural heritage. In this study, selected sorptive and mechanical...

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...

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...

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...

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...

Es werden methoden zur zerstötungsfreine Prüfung von Holz Zusammengestellt (Review Papaer). Schallausbreitung,Eigenfrewuenz,Thermographie, optische Verfahren, Durchstrahlung

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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-...

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...

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...

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...

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...

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...

Moisture induced strain and delaminanation in glued wood under dry conditions in heated building (problemens, open investigations)

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...

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...

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...

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...

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.

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...