Thermo-directional movement of wood and wood composites

Summary Thermal movement of wood and wood composites was studied and compared with that of random and oriented phenolic foams. Cell orientation was a dominate factor determining the thermal response of these structures. In dried wood, thermal movement in the direction parallel to the cells (longitudinal) decreased in dimension during heating while the radial and tangential directions expanded under similar heating condition. Oriented foams showed more restraint in thermal movement in the parallel to orientation direction. These findings indicate constraining forces act on the direction parallel to the cells while more flexibility exists in perpendicular directions. Wood element size and orientation and the manufacturing process also influence the thermal response in wood composites. The experimental results also revealed the potential fire hazard of waferboard type of composites.     

State of research and trends in development of wood adhesives

We aim to present an overview of the status of adhesives in the wood industry,     

木塑复合材料生产工艺与发展前景

木塑复合材料是一种既类似木材又优于木材的新型复合材料,其加工工艺与传统木质人造板产品有较大的差别.本文介绍了木塑复合材料的加工工艺与产品性能特点,论述了木塑复合材料的发展趋势及应用前景.     

Improved interaction between wood and synthetic polymers in wood/polymer composites

Summary This article describes the properties of wood polymer composites consisting of linear low density polyethylene (LLDPE) and wood flour (WF). In an attempt to improve the interfacial adhesion between the matrix and the filler, different compatibilizers were used. The interaction between polymer and wood were studied by comparing LLDPE/WF composites with composites when compatibilizer was added. The experimental measurements were conducted by impact and tensile strength testing and Scanning Electron Microscopy (SEM). The mechanical properties of the composites were improved with SEBS triblock copolymer modified with maleic anhydride and with the ionomer polymer, Surlyn, as compatibilizers. SEM fractography confirmed better adhesion between wood particles and LLDPE matrix when SEBS was present.This study was financed by the Swedish National Board for Industrial and Technical Development (NUTEK) which is gratefully acknowledged     

我国木材科学研究的现状与发展趋势

从木材科学研究的内容出发,分析了我国木材科学研究的现状,并对我国木材科学研究的发展趋势做了深入的探讨,指出今后我国木材科学研究将向着多学科、更先进的研究方向发展。     

Damping and layer configuration in wood veneer composites

The aim of the present study was to find and describe the relationship between damping properties and both the number of layers and the fiber orientation in wood-veneer-composite specimens. The testing apparatus was a simple torsional pendulum in which the frequencies of the resulting free vibrations were maintained between 13 and 23 Hz. Cross-sectional (30 × 30 mm) specimens with a total length of 250 mm were used. The specimens were cut from manufactured wood-veneer-composite panels (both 0°/90° and 0°/0° oriented) with up to 13 layers. Existing problems such as nonlinearities, which are often responsible for weighting results, were taken into account by using several mathematical approaches. The results led to a consistent picture of the damping properties across the measured range. We found that the damping ratio increased for the 0°/90° orientation with increasing numbers of layers in a cross-sectional specimen of constant outer dimensions. This effect could not be reproduced for specimens oriented 0°/0°.     

Research advance in wood composites in China

Inthe21stcentury,thewoodsupplyinChinawillcontinLJetobelessthanthedemand,soChinawillneedtousewoodasetfectivelyasPossible.Theuseotwoodcompositesisaveryefficientwaytosavewood.ChinalackssLJfficientforeststomeetitsdemandforwood,especiallyinfinequalitywoods.BecauseofChina'spopulationandfiberdemand,efficientuseofwoocJismoreimportanttoChinathanthattosomeothercoLJntries.However,Chinawasneitherconvincedofthisandnordiditpayattentiontothestudyofwoodcompositesbeforethe1970's.FacingthewoodcrisisChinaf…     

Development of wood and wood ash-based hydroxyapatite composites and their fire-retarding properties

For making efficient use of waste wood ash emitted from wood biomass plant, the wood and wood ash-based hydroxyapatite (HAp) composite was produced and their flammability characterization was studied by thermogravimetric (DTA-TG) analysis, oxygen index (OI) measurement and cone calorimeter test. The results show that the exothermic and weight loss peaks in DTA-TG combustion profiles due to their significant thermal decomposition were weakened by the HAp agent impregnation. In addition, the OI value of HAp composites was increased by the HAp combining and the OI showed a correlation with the HAp contents. Also, the cone calorimeter study revealed that the heat release rates were decreased with increasing amount of HAp injection and accordingly their total heat release has an inverse relationship to the HAp contents. These results indicate that the treatment with wood ash-based HAp agents can enhance the flame retardancy of the treated woods.     

关于日本木材进口结构变化的分析

90年代以来,日本木材进口量上下波动,自给率下降。加工品进口增加和木质板替代实木产品,进口与流通渠道的多样化,进口国的分散化,进口关税的下降,都逐步改变着日本的木材进口结构和供需结构。国际木材贸易与日本国内宏观经济背景、木材市场、林产工业、林业等各种因素的相互作用是产生这些结构性变化的原因。这些变化将进一步加强日本对进口木材的依赖,促进日本国内林产工业的衰退,日本对国际木材市场特别是高附加值加工产品市场的影响力也会因此而提高。     

STUDY ON WOOD COMPOSITES DENSITY UNIFORMITY BY X-RAY

X-ray is irradiated in some wood composites(multi-layer particleboard.sin-gle-layer particleboard,reconsolidated wood,).According to the gray degree principle(0-255 grade degree)and the corresponding relation between density and gray,X-raynegatives are scanned.The numbers and pictures of every degree density are obtained andaccurate composite densities are counted.     

Mode III fracture energy of wood composites in comparison to solid wood

A simple experimental setup for mode III and mixed mode (I?+?III) fracture tests with anisotropic materials under steady state crack propagation has been developed. Load-displacement curves can be recorded up to the complete separation of the specimen. From the load-displacement curves several mechanical material parameters can be derived. The tests have been performed for solid wood and different wood composites, being PARALLAM^® PSL in different orientations, particleboard and INTRALLAM^® LSL, and the fracture behaviour is characterised by the specific fracture energy.     

Evaluating durability of thermoplastic wood composites against basidiomycetes and development of a suitable test design

Abstract

Wood polymer composites (WPC) consist mainly of wood particles from non-durable softwoods. From experience in service life and laboratory testing it is known that WPC is not fully resistant against biological attack. Concerning durability testing, it is difficult to reach sufficient moisture content for fungal growth in the time frame of testing. Furthermore, the interpretation of test results is difficult, since the mass loss is measured but strength loss might be more important during service life. The relation between mass loss and strength loss is not deeply explored so far. Additionally moisture uptake causes an irreversible strength loss of WPC. Considering these problems a new test method for investigating the resistance of WPC against basidiomycetes is described in prEN 15534-1. In this paper, several test methods were carried out regarding their suitability for durability testing of WPC. The tests included various pre-wetting methods. After durability testing the mass loss and changes in strength and stiffness were evaluated. The results have shown that pre-wetting according to EN 84 is suitable to increase the moisture content. Furthermore strength and stiffness loss is higher than mass loss. The loss in mechanical properties is based on moisture uptake as well as fungal decay.     

木材无损检测技术的研究现状与进展

本介绍了木材无损检测技术的主要方法和基本原理,以及不同木材特性的无损检测技术,阐述了几个主要检测技术如超声波,射线,微波等的研究现状及存在的问题,在此基础上,提出木材无损检测技术的发展趋势。     

Performance of thermomechanical wood fibers in polypropylene composites

ABSTRACT

Thermomechanical wood fibers, as usually used for medium density fiberboard or cardboard production, feature promising characteristics, like a high aspect ratio, for the utilization in thermoplastic composites. The present study investigates the influence of fiber loading and fiber geometry on the mechanical properties of wood-polypropylene composites in order to confirm the results that were found in a previously published literature review. Composites were compounded at fiber contents from 20 to 60 wt.%, using a co-rotating twin-screw extruder and subsequently injection molded to test specimens. Field emission scanning electron microscopy was carried out to evaluate the fracture morphology of the composites. Fiber length was evaluated using an applying a dynamic image analysis system. Compounding reduced fiber lengths up to 97%. The mechanical properties decreased with increasing fiber content for composites without a coupling agent. Strength properties peaking at a fiber content of 50?wt.% for composites containing MAPP. Tensile strength and flexural strength reached 48.1 and 76.4 MPa, respectively. However, it was found that the processing of these fibers into conventional compounding equipment is still challenging.     

Preservative properties of vapor-boron-treated wood and wood-based composites

The treatability of wood (sapwood ofCryptomeria japonica D. Don) and wood-based composites (particleboard, waferboard, medium-density fiberboard, plywood) with vapor-boron was good, and the treated materials proved to be resistant to decay fungi and subterranean termites in laboratory bioassays. No difference in effectiveness was noted between vapor-boron and liquid-boron treatment of wood. Toxic threshold values determined for solid wood were 0%–0.24%, 0.26%–0.51%, and 0.26%–0.51% BAE (boric acid equivalent), respectively, against the white-rot fungusTrametes versicolor (L.: Fr.) Pilat, the brown-rot fungusFomitopsis palustris (Berk. et Curt.), and the subterranean termiteCoptotermes formosanus Shiraki. A concentration of less than 1% BAE seemed sufficient to control biological attacks on composites, although the toxic limits could not be determined more accurately because of the tested range of boron retention. High boron retention was needed to meet the performance requirements for slow-burning materials when a fire-retardant agent was not incorporated into the glue line.     

The effect of elevated temperature exposure on the fracture toughness of solid wood and structural wood composites

Fracture toughness of wood and wood composites has traditionally been characterized by a stress intensity factor, an initiation strain energy release rate (G _init) or a total energy to fracture (G _f). These parameters provide incomplete fracture characterization for these materials because the toughness changes as the crack propagates. Thus, for materials such as wood, oriented strand board (OSB), plywood and laminated veneer lumber (LVL), it is essential to characterize the fracture properties during crack propagation by measuring a full crack resistant or R curve. This study used energy methods during crack propagation to measure full R curves and then compared the fracture properties of wood and various wood-based composites such as, OSB, LVL and plywood. The effect of exposure to elevated temperature on fracture properties of these materials was also studied. The steady-state energy release rate (G _SS) of wood was lower than that of wood composites such as LVL, plywood and OSB. The resin in wood composites provides them with a higher fracture toughness compared to solid lumber. Depending upon the internal structure of the material, the mode of failure also varied. With exposure to elevated temperatures, G _SS for all materials decreased while the failure mode remained the same. The scatter associated with conventional bond strength tests, such as internal bond and bond classification tests, renders any statistical comparison using those tests difficult. In contrast, fracture tests with R curve analysis may provide an improved tool for characterization of bond quality in wood composites.