An innovative method based on grain angle measurement to sort veneer and predict mechanical properties of beech laminated veneer lumber

This study proposes an innovative model based on local grain angle measurements to predict the modulus of elasticity of LVL made from beech. It includes a veneers sorting method industrially compatible thanks to its low computational time. For this study 41 LVL panels were prepared from 123 beech sheets of veneers. Local grain angle was obtained with a two dimensional scanner and veneer density was measured. Several models based on these measurements have been developed and their ability to predict the modulus of elasticity of LVL panels have been compared. The model based only on local grain angle measurements have been proven more efficient than models taking into account the veneer density. The proposed method can be used to sort veneer during the peeling process and grade the production of LVL panels to optimize their mechanical properties even for low-quality veneer.ANR-10-EQPX-16 XYLOFOREST ; Région Bourgogne Franche-Comté ; Brugèr

Impact of laser fading on physico-mechanical properties and fibre morphology of multicomponent denim fabrics

Laser fading technology is used to give a unique worn look to a fabric. This finishing technique is environmentally friendly compared to conventional methods because it reduces the use of harmful chemicals and large amounts of water. A carbon dioxide (CO2) laser with a wavelength of 10.6 µm was used in this study. In bulk production, fixed manufacturing parameters help to reduce production preparation time. Thus, two combinations of laser power and speed of the laser cutter head (14 W and 230 mm/s; 16 W and 350 mm/s) were used to determine how universal the fixed laser parameters are for fading five different types of multicomponent twill and satin weave denim fabrics, which contain cotton, elastane, polyester and viscose. Physico-mechanical properties (tear, tensile properties and abrasion resistance) were tested to evaluate the effect of the selected laser parameters on fabric strength properties. Microscopical analysis was performed to assess the effect of laser fading on the yarn and fibre morphology of denim fabrics

Lathe check development and properties: effect of log soaking temperature, compression rate, cutting radius and cutting speed during peeling process of European beech (Fagus sylvatica L.) veneer

The depth of lathe checks and integrity of veneer have been shown to be critical factors affecting the bonding process but also affecting the mechanical properties of veneer-based products. This study shows how beech (Fagus sylvatica L.) veneer lathe checks interval and depths are affected by soaking temperature, compression rate, cutting radius and cutting speed during the peeling process in well-controlled conditions. Freshly felled European beech logs were soaked in a water tank at 50, 60, 70 or 80 °C. Following soaking, the logs were immediately peeled with laboratory scale lathe (SEM S500) to 3.5 mm thick veneer at a cutting speed of 1, 2 or 3 m s−1 and pressure rates of 0, 5, 10 or 15%. The correlation between lathe check depth and frequency was validated using “Système de Mesure d’Ouverture des Fissures” (SMOF) device, which enables to measure check properties reliably on veneer ribbons. In a well-controlled peeling process, the strong correlation between check depth and interval was shown. At higher temperature, shallower and more frequent checks are created compared to lower temperature. However, the effect of soaking temperature (between 50 and 80 °C) on veneer checking is much smaller than the effect of compression rate during peeling process, where the higher compression rate produced veneer with shallower and more frequent checks. The results of the study also show that the direction of lathe check propagation could be affected by the rays in beech veneer. Rays resist crack growth in tangential direction, but act as weak planes in radial direction.ANR-10-EQPX-16 XYLOFOREST ; Région Bourgogne Franche-Comt

Haudonnan vaikutus koivuviilun pinnan laatuun, liimasauman muodostumiseen ja vanerin liimasauman lujuuteen

Bond formation and performance in veneer-based products is highly dependent on veneer quality, which in turn can be affected by processing factors including log pre-heating conditions. Hence, it has been shown that the heating of logs enhance many veneer and plywood properties, the mechanisms behind the bond strength increase is not fully understood. Therefore, the main focus of this dissertation was to investigate the effects of the pre-heating process on the surface properties of veneer and its potential to improve bond quality. Additionally the applicability of commonly used test methods to evaluate the effect of pre-heating temperature on surface properties and bonding quality were assessed. This series of studies clearly show that lathe check depth and pulling direction have a strong influence on the measured shear strengths of plywood tested according to SFS-EN 314, even though this is a test for adhesive bonding and not intended for measuring wood quality. Therefore, controlling lathe checks properties could result in much lower variability in wood bonding tests allowing researchers to more easily identify other factors influencing bond quality, e.g. felling season and pre-heating temperature. This study also indicated that log pre-heating temperature not only causes the softening of material in the rotary peeling process, but also causes irreversible changes in the wood material which subsequently has an effect on bond strength development. Results show that the temperature history of the log prior rotary peeling is an important factor which contributes to veneer properties and bond strength. Furthermore, the interpretation of adhesion data obtained by ABES should be treated with caution in situations where the veneer properties and history are not fully known. Assuming that veneer is a homogenous substrate might lead to a misinterpretation of results obtained by ABES. The results of the study show that winter felled birch logs are most susceptible to the effects of pre-heating temperature and heating birch at low temperature leads to remarkable variation in the results caused only by seasonal variation. When paying attention to the aforementioned issues, ABES was found to be very useful for evaluating the impact of veneer production variables or the wood properties on the bonding process. The advantage of the surface integrity measurements technique developed in this study is that it evaluates the particles loosely attached to surface, which could act as a locus of failure in the bondline and cannot be evaluated by roughness measurement techniques. Finally, while the bonding quality of plywood is driven by the uncontrolled effects of lathe checks, further development of bonding and new adhesive concepts will be complicated.Liimasauman muodostuminen ja suorituskyky viilupohjaisissa tuotteissa riippuu hyvin pitkälti viilun laadusta, johon voidaan vaikuttaa valmistusprosessin osavaiheiden, kuten haudonnan, avulla. On osoitettu, että tukkien lämmitys parantaa monia viilun ja vanerin ominaisuuksia, mutta liimasauman lujuuden kasvuun vaikuttavia mekanismeja ei vielä täysin ymmärretä. Siksi väitöskirjatyön päätavoitteena oli tutkia haudonnan vaikutusta viilun pinnan ominaisuuksiin ja liimasauman laatuun. Lisäksi tutkittiin, soveltuvatko yleisesti käytetyt liimasauman testausmenetelmät haudontalämpötilan vaikutuksien arviointiin. Väitöskirjan osatutkimukset osoittavat selvästi, että sorvaushalkeamien syvyydellä ja vetosuunnalla on suuri vaikutus SFS-EN 314 -standardin mukaan mitattuun vanerin liimasauman lujuuden arvoon, vaikka kyseinen koemenetelmä on tarkoitettu liimasauman, ei viilun laadun, testaamiseen. Siksi sorvaushalkeamien ominaisuuksien hallinta voisi johtaa paljon pienempään hajontaan vanerin liimasauman testauksessa mahdollistaen sen, että tutkijoiden olisi helpompi tunnistaa muut liimasauman laatuun vaikuttavat tekijät, kuten hakkuukausi ja haudontalämpötila. Väitöstutkimus osoitti myös, että tukkien haudontalämpötila paitsi pehmentää materiaalia sorvausta varten, myös muuttaa puumateriaalia peruuttamattomasti vaikuttaen liimasauman lujuuden kehitykseen. Tulokset osoittavat, että tukin lämpötilahistoria ennen sorvausta vaikuttaa merkittävästi viilun ominaisuuksiin ja liimasauman lujuuteen. Lisäksi ABES-testien tulosten tulkintaan pitäisi suhtautua varauksella tilanteissa, joissa viilun ominaisuudet ja historia eivät ole täysin tiedossa. ABES-tulokset saatetaan tulkita väärin, jos viilun oletetaan olevan homogeeninen alusmateriaali. Väitöstutkimuksen tulokset osoittavat, että talvella kaadetut koivutukit ovat kaikkein altteimpia haudontalämpötilan vaikutuksille ja koivutukkien haudonta alhaisissa lämpötiloissa aiheuttaa huomattavaa vaihtelua tuloksiin, jotka johtuvat ainoastaan kausivaihtelusta. ABES-testauksen havaittiin olevan erittäin hyödyllinen arvioitaessa viilun tuotantoparametrien tai puun ominaisuuksien vaikutusta liimaukseen, kunhan edellä mainitut asiat huomioidaan. Tässä tutkimuksessa kehitetyn pinnan eheyden mittaamismenetelmän etuna on, että sen avulla voidaan arvioida heikosti pinnassa kiinni olevien partikkeleiden määrää, joita pinnankarheutta mittaamalla ei voida havaita. Näiden partikkelien keskittymä saattaa toimia liimasauman murtumisen alkupisteenä. Sorvaushalkeamat vaikuttavat merkittävästi liimasauman lujuuden mittaustuloksiin, mikä vaikeuttaa liimauksen ja uusien liimausjärjestelmien jatkokehittämistä

Estimating birch veneer (Betula pendula Roth) moisture content using infrared technology

International audienceThe potential of infrared (IR) technology in estimating the moisture content (MC) of birch (Betula pendula Roth) veneer was investigated. A total of 56 birch veneer sheets (42 × 130 cm2) were dried with a convective type laboratory-scale veneer dryer at drying times ranging from 1 to 6 min at 1 min intervals. After drying, IR data were recorded and the veneer sheets were sawn into 100 × 100 mm2 pieces. IR data were averaged over the same area and then the true MC and density values were assessed gravimetrically. The dependency between temperature and MC was found to be non-linear and between temperature and density there was no dependency. The relationship between temperature and MC was modeled with a neural network and a Gaussian model. Both model types gave similar results. At a true MC below 10 %, the root mean square error of prediction (RMSE) was 1.5 % for the 100 × 100 mm2 pieces and 1.2 %, for the larger veneer sheets, whereas at higher MC (above 10 %), the RMSE increased to 2.6 % for the 100 × 100 mm2 pieces and 1.9 % for the sheets. It was observed that the IR measurement should be taken within 5 s, since after that the RMSE increased rapidly. Based on the results of this study, it was concluded that veneer MC can be estimated with reasonably good accuracy using IR technology

Impact of Aspen and Black Alder Substitution in Birch Plywood

Increasing demand pressures on the fibre supply are forcing manufacturers to explore using new species in plywood. Here we investigated aspen and black alder, alone and in combination with birch faces, and with different veneer thicknesses in plywood production. The aim of this study was to evaluate the effect of different veneer thicknesses, lay-up systems, and hardwood veneer combinations on plywood mechanical properties. Impacts on modulus of rupture (MOR), modulus of elasticity (MOE), glue consumption, and density properties were observed. All process parameters were the same as for pure birch plywood. Not surprisingly, birch plywood had the highest MOR and MOE, followed by aspen and black alder. Aspen had the highest glue consumption and birch the lowest, when applied with a spreader roll, but the common practice of using relatively thick 2.6 mm aspen veneers resulted in the lowest glue consumption per mm of product. The effects of wood species and veneer thickness on MOR, density, and glue consumption were analysed for panel thicknesses from 6.5 to 18 mm to guide manufacturers in choosing their species and construction to optimize cost, MOR and stiffness, weight, and glue consumption. In conclusion, birch gave the best strength properties while aspen gave the best price and weight combination