试样尺寸对木材物理力学性质的影响

根据最弱链模型和纤维束模型理论,探讨了试样尺寸对木材物理力学性质的影响原理;并对不同木材性质作了定量分析.结果表明:木材物理性质一般受试样尺寸的影响较小;木材力学性质则不同程度地受到其影响.其中,抗拉强度受的影响最大,抗压强度最小,在对木材力学性质测试时,一般应考虑试样尺寸的影响.     

江苏池杉木材物理力学性质

池杉(Taxodium ascendens Brongn.)又称池柏,原产美国东南部和墨西哥的东北部沿海平原沼泽地、低湿地。在我国池杉最早于1927年引种南京,30年代后相继引种至武汉,南通和广州等地。70年代江苏栽植较多,特别里下河地区发展更快。据统计,扬州市现有片林近5万亩,不少已成林、成材。池杉已成为江苏速生丰产林的主要树种之一。但对其木材的材性和用途尚缺乏了解,至今末见报道。因此,我们对里下河地区池杉木材的物理力学性质等,进行了测试和分析研究,以便为今后采伐利用和进一步的发展提供科学依据。 试材与方法 1988年4月下旬,在金湖县宝应湖农场     

文县杨木材物理力学性质试验分析

在木材物理力学性质试验的基础上,研究了文县杨木材的9种常规物理力学性质,并对其材性指标进行了评价。结果表明,文县杨木材生长速度快,密度很小,顺纹抗压,抗弯及抗剪强度均低,抗弯弹性模量和冲击韧性中等。对比分析可知其木材物理力学性质与杨属类其它种木材相近,并指出其木材利用的主要方向。     

杨村新无性系木材物理力学性质的研究

研究了7个杨树新无性系和I－69杨的木材物理力学性质。结果表明，杨木新无性系的物理力学性质等主要指标均属于小至甚小级，无性系间物理力学性质差异显著，据此可用木材物理力学性质因子选育优良无性系。尽管新无性系的生长速度超过I－69杨，但由于其某些强度指标低于I－69杨，8年生的速生材尚不能完全替代11年生的I－69杨使用，因此不能作为建筑结构材使用。     

贵州马尾松人工林木材物理力学性质研究

本文对贵州林科院试验林场生长的人工林马尾松木材物理力学性质进行了测定，并与贵州产45年树龄的天然林木材的主要强度指标作了比较。结果表明：人工林马尾松木材基本密度、全干缩率、顺纹抗压强度、抗弯强度和抗弯弹性模量在幼龄材与成熟材之间存在显著差异。而人工林与天然林之间的木材密度和主要强度指标差异不大。     

蝴蝶果木材的物理力学性质研究

采用国家标准GB1929—1943—130《木材物理、力学试验方法》对蝴蝶果木村进行物理力学性质试验,试验结果其年轮宽度平均为4.3mm,属速生树种。木材气干密度0.649/cm~3,体积干缩系数0.516％,顺纹抗压强度464kgf/cm~2抗弯强度955kgf/cm~2,抗弯弹性模量123 1000kgf/cm~2,端面硬度558kgf/cm~2,木材均属中等,它与同科秋枫、黄桐、鸟柏相此,排列第二,但木材均属中等一级。木材纹理直,结构均匀,易加工,是纺织业,建筑业、轻工业、家具和制浆造纸等用材。(编辑)     

人工林日本落叶松木材物理力学性质的研究

通过试验和统计分析的方法，研究了人工林日本落叶松木材的物理力学性质及其与密度与主要力学强度的相互关系。结果表明；人工林日本落叶松硬度和主要力学强度适中，与长白落叶松和兴安落叶松相比，日本落叶松结构相对均匀，弦径干缩差异性小，可满足各种木制品的生产要求。     

豫南引种檫木木材物理力学性质的试验研究

为了檫木的推广,我们对豫南引种檫木木材的物理力学性质进行了试验分析,并与原产地檫木木材进行比较。结果表明,豫南引种檫木的木材物理力学性质指标与中心产区差别不大,其木材强度适中,加工性能好,可广泛用于建筑、船舶、交通运输、胶合板等工业领域。     

大叶相思木材的物理力学特性

前言大叶相思(Acacia auriculiformis)原产巴布亚新几内亚的萨温纳斯(托雷斯海峡诸岛)和澳大利亚北部。由于它能在极瘦瘠的土壤上生长,已为许多国家所引种,如印度尼西亚、马来西亚、坦桑尼亚和尼日利亚等。该树种生长旺盛,在原产地树高达30m、干径达60cm。它又是一种受人喜爱的观赏和遮荫树木,管理十分粗放。巴布亚新几内亚10年生大叶相思人工林的有关资料表明,其制浆产量高,力学性能好。     

三种速生杨木材物理力学性质的比较研究

测试、分析比较了不同树龄3种速生杨木材的物理力学性质,结果表明:①树种对物理力学性能有较大的影响,三倍体圆叶毛白杨的物理力学性能最好,三倍体裂叶毛白杨次之,中林-46最差;方差分析表明,3种杨树的主要物理力学性质均达到显著和极显著差异。②树龄对物理力学性质的影响不大,随着树龄的增长,不同杨树木材的密度已趋于稳定,但力学性能有上升的趋势;方差分析表明,抗截切强度和抗弯强度受树龄影响较大,差异达到显著水平,其他性质无显著差异。     

树龄对日本落叶松木材物理力学性质的影响

选取日本落叶松为试验材料,开展不同树龄日本落叶松物理力学性质的比较研究.结果表明:43年生、30年生和17年生日本落叶松木材气干密度分别为0.607,0.567和0.507 g/cm3,气干体积干缩率分别为7.7％,7.7％和7.1％;全干到气干体积湿胀率分别为5.1％,4.9％和4.5％;抗弯弹性模量分别为17.527,16.775和12.510 GPa,抗弯强度分别为121.1,110.3和90.9 MPa,顺纹抗压强度分别为56.8,51.8和44.0 MPa.随着树龄增大,日本落叶松木材密度、顺纹抗压强度、抗弯强度和抗弯弹性模量等各项物理力学性能指标提高,差异干缩逐渐变小.日本落叶松木材的气干密度与抗弯弹性模量、抗弯强度、顺纹抗压强度呈线性正相关,相关系数分别为0.760,0.816和0.900.     

The role of vascular bundles on the mechanical properties of coconut palm wood

This study examines certain physical, mechanical, and anatomical characteristics of coconut palm wood. The results show a correlation between the anatomical characteristics and density as well as lengthwise compression. All properties (density, frequency of vascular bundles (VBs), and mechanical properties) increase with the transverse distance from the center of the trunk. The study also tests VBs from different radial sections of the coconut palm tree (Cocos nucifera) for diameter, ultimate tensile strength, and modulus of elasticity. The influence of the VBs on the overall properties of the wood is discussed.     

The effect of compression and incision on wood veneer and plywood physical and mechanical properties

ABSTRACT

Drying takes the largest share of energy in plywood production, and varying moisture content of veneers necessitates re-drying that often leads to over-dry veneers with deactivated surfaces, which may promote imperfect bonding. In order to decrease the drying time, reduce the need for re-drying of veneers, and improve the quality of plywood, birch and spruce veneers were subjected to pre-treatment by cold compression, incision, or a combination of the two. The effects of pre-treatment on the veneer and plywood quality were assessed by standard tests. Compression had a beneficial effect on water removal of the wettest veneers (spruce sapwood (SW) and birch), but some thickness reduction was observed in the veneers as well as the finished birch plywood. Compression led to thickness reduction of spruce veneers, but had no effect on SW plywood thickness likely due to higher viscoelasticity. Both compression and the combination of incising and compression levelled the moisture variation within the compressed stacks. Incision improved the modulus of elasticity of birch plywood, shear strength of SW plywood, and both bending and shear strengths of heartwood plywood. Higher surface pressure decreased the drying time of spruce SW in both plain compression and combined incision and compression pre-treatment.     

Effects of impregnation and heat treatment on the physical and mechanical properties of Scots pine (Pinus sylvestris) wood

Wood modification, of which thermal modification is one of the best-known methods, offers possible improvement in wood properties without imposing undue strain on the environment. This study investigates improvement of the properties of heat-treated solid wood. Scots pine (Pinus sylvestris) was modified in two stages: impregnation with modifiers followed by heat treatment at different temperatures. The impregnation was done with water glass, melamine, silicone, and tall oil. The heat treatment was performed at the temperatures of 180°C and 212°C for three hours. The modified samples were analyzed using performance indicators and scanning electron microscope micrographs. The mechanical and physical properties were determined with water absorption, swelling, bending strength, and impact strength tests. All the modifiers penetrated better into sapwood than hardwood; however, there were significant differences in the impregnation behavior of the modifiers. As regards the effect of heat treatment, generally the moisture properties were improved and mechanical strengths impaired with increasing treatment temperature. In contrast to previous studies, the bending strength increased after melamine impregnation and mild heat treatment. It is concluded that the properties of impregnated wood can be enhanced by moderate heat treatment.     

Effects of nanoclay on physical and mechanical properties of wood-plastic composites

Effects of nanoclay (NC) on physical and mechanical properties of wood-plastic composite (WPC) were studied here. Virgin, recycled, and mixed (50/50% of virgin/recycled) polyvinyl chloride (PVC) were used as the matrix in the WPC. Specimens with three NC contents of 1.5%, 3%, and 5% were manufactured; they were then compared with control specimens. Totally, 12 treatments were manufactured. The physical and mechanical properties were measured in accordance with the ASTM standards. The highest properties were found in specimens made from virgin PVC. Addition of recycled PVC resulted in significant decrease in all properties. NC improved all physical and mechanical properties studied in the present research project; the highest properties were observed in specimens with 5% of NC content. The improvement in properties was as a result of formation of bonds between the hydroxyl groups of NC with the wood flour components. It was concluded that NC would significantly improve the properties in all the three PVC types of virgin, recycled, and mixed. From an industrial point of view, it was concluded that mixing virgin and recycled PVC can be recommended not only to decrease production costs, but also to partially solve the problem of PVC residue which are not bio-degradable.     

Selected physical and mechanical properties of the Chilean wood species roble,lingue, manio and alerce

Abstract

Data sets with mechanical and physical properties of wood species can aid the recognition of biomechanical correlations, and they can also be valuable tools to assist decision making regarding the practical industrial employment of the species. However, such data sets are still lacking for many species, particularly non-European and non-North-American species. Therefore, the goal of this study was to determine the mechanical properties of four Chilean species (the softwoods alerce and manio, and the hardwoods lingue and roble), including the three Young's moduli and the three shear moduli. Dynamic methods were applied as well as static ones. The results suggest that Brinell hardness, compression strength and Young's moduli are clearly correlated with the density and can partly be related to anatomical details. Since the investigated species cover only a fraction of the Chilean species that are suitable for construction purposes, for example, further future examination of relevant species would be beneficial for basic research and industry.     

闽南格木木材物理力学性质的研究

通过对格木木材物理力学性质进行测定和分析,结果表明:格木木材密度大、变形大,其气干密度为0.857 g·cm-3,基本密度为0.746 g·cm-3,体积干缩系数为0.615,顺纹抗压强度为67.59 MPa,抗弯强度为141.82 MPa,综合强度为209.41 MPa,属于高。该研究结果解决了格木营林和木材利用上的一个基础性问题。     

STUDIES ON PHYSICAL AND MECHANICAL PROPERTIES OF DAHURIAN LARCH-WOOD OF TWO WOOD COLOURS

Dahurian1arch[Larixgmelini(Rupr.)Rupr.jisamaintimbertreespe-ciesinDaxing'anLingForestRegion,and'itisalsoafast-growingandregenerationtreeinNorthChina-Becauseitsecologicalamplitudeisverywild,therearemanyva-riabletypesinvarioushabitats.Themostsignificativetypes,whichhavebeenfoundrecentlyininvestigation,aretheredwoodandwhitewood.Theformerisfromyellow-browntored-brown,andthelat-tCrisfrompaleyellowtowhite.Theyaresimilarto'Redscotchpine#and'Whitescotchpine#.Theparametersofwoodcol-ourandphysico-…     

木纤维PP/PE共混物复合材料的流变和力学性能(英文)

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.