全 文 ：Journal of Forestry Research, 16(4): 299–300 (2005) 299


Effect of moisture and fungal exposure on the mechanical properties of hem-fir
plywood

WANG Wei-hong1, Scott Kent2, Camille Freitag2, Rorbert J. leichti2, Jeffrey J. Morrell2
1 Key Lab. of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040, P. R. China
2 Department of Wood Science and Engineering, Oregon State University, USA

Abstract: Hem-fir plywood were exposed to two brown rot fungi, Gloeophyllum trabeum and Postia placenta, and one white rot fungus,
Trametes versicolor, to investigate the effect of fungal decay on mechanical properties of plywood. Results showed that modulus of rupture
(MOR) and modulus of elasticity (MOE) of hem-fir plywood declined significantly by inoculating fungi, and weight loss of sample had a
modest decrease. The fungi also made a greater effect on MOR than on MOE. Of three fungi, Postia placenta caused a most significant
weight loss, and Gloeophyllum trabeum resulted in a largest flexural properties loss. Substantial declines in MOR and MOE of hem-fir ply-
wood were also observed when the plywood samples were stored under wet conditions over 15 weeks, even in the absence of fungal attack.
Keywords: Fungus decay; Weight loss; Flexural properties; Moist condition; Plywood; MOR, MOE
CLC number: S781.2 Document code: A Article ID: 1007-662X(2005)04-0299-02



Introduction

Plywood has been a kind of dominant materials for sheathing
in houses and buildings in the past several decades. Generally the
composite durability is related to the decay progress that is nor-
mally evaluated based on the weight loss or visual assessment.
Many literatures have shown that the early stages of fungal decay
were often characterized by dramatic decreases in some me-
chanical properties, but with only modest losses in wood com-
ponents and minimal changes in appearance (Wilcox 1978;
Scheffer 1936; Green et al. 1991; Winandy and Morrel 1993;
Imamura 1993; Kim and Ra 1996; Petersen and Schwandt 1991;
Schmidt et al. 1978). Therefore, the method of normal decay
evaluation may not truly reflect the changes of some mechanical
properties caused by fungal attack.
The objective of this research is to determine the effect of rot
decay and white decay on bending properties of plywood, so as
to develop an effective method for evaluating the decay and the
residual service-life of wood and composite materials under ad-
verse conditions.

Material and methods

Samples (330 mm × 76 mm) came from the commercially
produced hem-fir plywood (5 ply, 12 mm in thickness), which
were oven-dried (104°C) and weighed. In order to get high
enough moisture content, samples were immersed into water in a
pressure vessel, subjected to a vacuum with 30 min, and then
raised to a pressure of 550 KPa with 90 min. The moisture con-
tent of treated samples reached a range of 80% to 90%.
Sets of plywood strips were sealed and laid flat in autoclave-
able bags and autoclaved for 30 min at 120°C. Then the bags
were heat-sealed and refrigerated to ambient. Each bag was cut a

Foundation item: This research was supported by Forest Research Labora-
tory, Oregon State University.
Biography: WANG Wei-hong (1968- ), female, Ph.D., associate professor of
Northeast Forestry University, Harbin 150040, P.R. China.
Email: weihongwang2001@yahoo.com.cn
Received date: 2005-01-22; Accepted date: 2005-04-21
Responsible editor: Song Funan
20 mm slit and injected sterile air and 200 μL suspension of hy-
phal spore on sample surface. Then, the slits were resealed with
tape and the bags were incubated at 30°C. And similarly bagged
specimens without fungal inoculum were established to serve as
controls. The fungi employed in test were brown rot fungi,
Gloeophyllum trabeum (Pers ex Fr.) Murr. (Isolate Madison 617)
and Postia placenta (Fris) M. Larsen et Lombard (Isolate Madi-
son 698), and white rot fungus, Trametes versiclolor (L. ex Fr.)
Pilat (Isolate Madison R105).
Samples were exposed to fungi for 5–15 weeks after inocula-
tion. Six samples exposed to each fungus were removed after
every 5 weeks, then oven-dried and weighed to determine wood
weight loss. The samples reached a stable weight at 20°C and
60% of relative humidity. Modulus of rupture (MOR) and
modulus of elasticity (MOE) of these samples were detected
according to the procedures described in D 1037 (ASTM2002). A
50-mm section was removed from the end of the each test
specimen to determine the moisture content.

Results and discussion

Weight loss is a traditional measure to evaluate the ability of
fungi to utilize cellulose, hemicellulose, and lignin structural
polymer of the wood cell for nutrition. The test results showed
that three fungi attacked inoculated samples rapidly and caused
increasing weight loss and strength reduction over the exposure
of 15 weeks (Table 1). Although all of the inoculated samples
were colonized by fungi, they were more susceptible to Postia
placenta decay, which resulted in most weight loss during the
period of treatment. Gloeophyllum trabeum and Trametes versi-
color grew slowly, and there is not significant difference in
weight loss between the two fungi during the first 15 weeks. The
difference of weight losses reflected the relative ability of fungus
to degrading materials.
The effects of fungi decay on mechanical properties are shown
in Fig. 1 Even though at the same level of weight loss, sample
properties also showed different change. These differences exist
not only between brown decay fungus and white decay fungus,
but also between brown fungi, such as between Gloeophyllum
trabeum and Postia placenta. Therefore, weight loss is a rela-
WANG Wei-hong et al. 300
tively insensitive measure and can not reflect the real damage induced by fungi decay to the mechanical properties of materials.
Table 1. Effect of moist and fungal exposure on the MOR and MOE of hem-fir plywood
Average MOR (MPa) Average MOE (GPa) Average mass loss (g) Exposure period
(week) Gloeophyllum
trabeum
Postia
placenta
Trametes
versicolor
Gloeophyllum
trabeum
Postia
placenta
Trametes
versicolor
Gloeophyllum
trabeum
Postia
placenta
Trametes
versicolor
0
44.35
(11.59)
44.35
(11.59)
44.35
(11.59)
6.25
(1.57)
6.25
(1.57)
6.25
(1.57)

5
46.34
(8.91)
43.31
(8.60)
35.56
(3.75)
6.51
(0.92)
6.51
(0.92)
5.36
(0.50)
2.20
(0.53)
2.53
(0.69)
2.20
(0.34)
10
29.55
(6.25)
27.33
(4.99)
27.17
(4.53)
4.60
(0.46)
4.43
(0.57)
4.15
(0.57)
3.76
(0.84)
5.65
(1.12)
5.21
(0.76)
15
15.23
(2.45)
25.10
(2.31)
22.74
(3.61)
2.52
(0.28)
3.88
(0.32))
3.36
(0.51)
5.36
(0.85)
6.28
(2.38)
5.84
(1.79)
Note: Values in parentheses are standard deviations









Fig. 1 Relationship between mass loss and MOR and MOE
Note: G.T. ---G. trabeum, P. P---P. placenta and T.V.---T. versicolor

The relative magnitudes of changes in flexural properties
caused by G. trabeum and T. versicolor were not consistent over
15-week exposure. When weight loss was less than 2 percent, the
flexural properties of sample treated by T. versicolor showed the
highest loss among the treatments. When weight loss was more
than 2 percent, the MOR of sample treated by G. trabeum had the
hightest percentage of loss. At the end of exposure, MOR of the
samples treated by G. trabeum lost 65.65%, which was corre-
sponded to a weight loss of 3.64%. In the entire test period, the
samples treated by P. placenta had the least quality deterioration
with a MOR loss of 43.31% and weight loss of 4.11% at the end
of test. Similar results were achieved in MOE. All three fungi
had more significant effect on the change of MOR (5%–10%)
than that of MOE.
Based on the test results, it is believed that brown fungi in-
duced substantial changes in material properties at relatively
early stages of attack, which was similar with results obtained by
Wilcox (1978). Usually, white rot fungi tended to preferably
decay hardwoods, but in this test, T. versicolor showed more
significant effect on MOR and MOE than P. placenta. T. versi-
color, and also caused significant decay to hem-fir material.
Typically, degradation of mechanical properties is often attrib-
uted to fungi colonization in fungi decay test. However, it is
worth noting that MOR and MOE in our test samples exposed
under wet condition in the absence of the fungus declined from
44.35 MPa to 33.34 MPa, and from 6.25 GPa to 5.06 GPa, re-
spectively, over the 15 week period. Similar effects occurred in
OSB and another kind of plywood test. Moisture content is one
of the most important factors required by fungi growth. It has
been found that the moisture content of 30% or more is neces-
sary for fungal growth (Highley 1999). Since the control samples
had high moisture content, test results implied that moisture
could be another key factor in weakening material properties.
As a rule, bonding strength should be greater than the strength
of wood component in composite in order to utilize wood fullest.
In our test, control samples obtained 75% moisture content. The
progressive effects with time implied a fundamental that mois-
ture can make an effect on the wood/resin interface. Declines in
properties were thought to be the result of separation between
wood and resins. Degradation resulted in not only from fungi
decay but also from the adverse effect of moisture.

Conclusion

Both brown and white rot fungi degrade MOR and MOE of
hem-fir plywood with modest weight loss, and MOR loss is more
than MOE loss. Strength losses of hem-fir plywood caused by
different fungus are different even at a same weight loss level. G.
trabeum showed the highest decomposing ability for hem-fir
plywood among the three testing fungi. Even though white rot
fungi usually tend to decay hardwoods, and T. versicolor attacks
hem-fir material at a slight weight loss, it had greater damage to
the properties compared with P. placenta.
It is difficult to differentiate the effects of the fungus on
hem-fir plywood from that of the water. Decrease of the bending
strength in control samples reflects the fact that moisture has a
serious opposite effect on the properties of hem-fir plywood, and
repeated wet-dry would accelerate this effect. While fungal
damage is often viewed as a serious concern, our test results
highlighted the importance of removing moisture sources not
only for avoiding fungal attack but also for reducing effects of
moisture induced on material properties.

References

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Imamura, Y. 1993. Estimation of the fungal resistance of wood composites for
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0
20
40
60
80
0 2 4 6
Weight loss (%)
M
O
R
lo
ss
(%
)
G.T. P.P.
T.V. Control
0
10
20
30
40
50
60
70
0 2 4 6
Weight loss (%)
M
O
E
lo
ss
(%
)
G.T. P.P.
T.V. Control
Chinese Abstracts
05-04-008
污染砂质土壤酸化对铜和锌释放影响的模拟研究/章明奎（浙
江大学环境与资源学院资源科学系，杭州 310029, 中国），
D.V. CALVERT（美国佛罗里达大学食品与农业科学学院印弟
安河研究与教育中心，FL 34945，美国）//Journal of Forestry
Research. –2005, 16(4): 289–292.
砂质土壤上造林会引起土壤酸化，影响铜和锌的释放。
本文用模拟方法研究了砂质耕地造林引起土壤酸化对土壤中
铜和锌释放的影响。结果表明，酸化可明显改变土壤中铜和
锌的化学形态，促使碳酸盐结合态铜和锌向交换态、有机质
结合态和氧化物结合态形式转化，增加土壤铜锌的释放和淋
出潜力，其中对锌的影响尤为明显。铜和锌溶解度明显增加
的土壤 pH 分别为 3.8-4.5 和 6.2-6.5。图 3 表 2 参 14。
关键词：铜；锌；污染砂质土壤；酸化；造林
CLC number: S154.4 Document Code: A
Article ID: 1007−662X(2005)04−0289-04

05-04-009
杉木冷冻干燥材和气干材液体浸注性的比较研究/吕建雄，林
志远，蒋佳荔，江京辉（中国林业科学研究院木材工业研究
所，北京 100091）//Journal of Forestry Research.–2005, 16(4):
293–295.
通过采用冷冻干燥方法和大气干燥方法对杉木
（Cunninghamia lanceolata（Lamb.）Hook.）人工林木材的心、
边板材进行干燥处理，用毛细管上升法评价干燥后试样的浸
注性能，用半薄切片法测定干燥试样具缘纹孔的闭塞率，最
后采用扫描电子显微镜（SEM）观察干燥试样微观构造的变
化，比较分析了两种干燥方法对杉木人工林木材浸注性的影
响机理。研究结果表明：与大气干燥相比，冷冻干燥能显著
提高杉木人工林木材心、边材的浸注性；两种干燥方法处理
后，杉木边材的浸注性均显著高于心材的浸注性；具缘纹孔
的闭塞率较低以及部分具缘纹孔的纹孔膜破裂是冷冻干燥后
木材渗透性提高的主要原因。表 3 图 4 参 14。
关键词：杉木；心材板材；边材板材；冷冻干燥；大气干燥；
液体浸注性；纹孔闭塞率
CLC number: TS652 Document code: A
Article ID: 1007-662X(2005)04-0293-03

05-04-010
一种新型磨盘成形技术研究 /向红亮（福州大学机械学院
350002）//Journal of Forestry Research.–2005, 16(4): 296–298.
本文研究了如何运用计算机技术三维制模、采用覆膜砂
造型、优化合金材料和利用计算机来控制打箱时间等新工艺
来生产磨盘。结果证明：利用计算机技术能减少制模时间，
提高产品的适应度；同时精密成形能减少磨盘的废品率；优
化合金材料和控制好打箱时间来消除淬火热处理阶段。与传
统的工艺相比采用这些改进措施，磨盘的制造工艺有增强韧
性、提高铸件精度、消除热处理阶段和提高生产效益等几方
面的优点。图 5 表 4 参 6。
关键词：磨盘；制模；精密成形；金属熔炼
CLC number: S776.038 Document Code: A
Article ID: 1007−662X(2005)04−0296-03

05-04-011
潮湿与真菌腐朽对室外用铁杉胶合板力学性能影响的研究/
王伟宏(东北林业大学生物质材料科学与工程教育部重点实
验室，哈尔滨 150040)，Scott Kent，Camille Freitag，Rorbert
J. leichti，Jeffrey J. Morrell（俄勒岗州立大学木材科学与工程
系，美国）//Journal of Forestry Research.–2005, 16(4): 299–300.
本文介绍了铁杉胶合板在真菌腐朽和潮湿状态下弯曲
强度变化的规律。对植真菌试件的研究结果表明，褐腐菌
Gloeophyllum trabeum 和 Postia placenta、白腐菌 Trametes
versiclolor 都对断裂模量和弹性模量造成严重破坏，而试件的
重量损失却很小，且断裂模量的下降幅度大于弹性模量。从
重量损失上看， Postia placenta 的生长最为旺盛，但
Gloeophyllum trabeum 腐朽造成的强度损失最大。未种植真菌
的对照组试件在 15 周的试验期间也表现出明显的强度下降，
由此说明室外用胶合板即使在没有真菌腐蚀的情况下，单纯
的潮湿仍会造成材料的强度下降，防止长期受潮不容忽视。
关键词：真菌腐朽，重量损失，弯曲强度，潮湿条件，胶合
板，MOR，MOE
CLC number: S781.2 Document code: A
Article ID: 1007-662X(2005)04-0299-02

05-04-012
森林道路对山雀类利用人工鸟巢的影响/朴容秀，李宇新（首
尔大学校山林科学部，韩国首尔(汉城) 151-921），任信在（中
央大学校动物资源科学科，韩国安城 456-756）//Journal of
Forestry Research.–2005, 16(4): 301–302.
于 2002 年 11 月至 2003 年 6 月间, 在韩国安养首尔大学
冠岳植物园(37°2505N,126°56 85E)阔叶林、针叶林和针阔
混交林内研究了森林道路对山雀类利用人工鸟巢的影响。对
在人工巢箱中繁殖的山雀类，杂色山雀(Parus varius)、沼泽山
雀( P. palustris)和大山雀(P. major)的繁殖对的数量、巢位、窝
大小、卵重及卵大小进行了调查。调查结果显示，在 3 个研
究区，杂色山雀在森林内部（距离道路 75–150m）的繁殖对
数量,比森林边缘(距离道路 0–75 m)多，其窝大小、卵重等尺
寸也明显比森林边缘高，但沼泽山雀基本不受森林道路的影
响。在人类活动频繁的地区人工巢箱为洞穴鸟类提供良好的
繁殖条件。人工鸟巢的设置将有利于这些鸟类的保护和管理。
表 3 参 16。
关键词：人工鸟巢；繁殖；森林道路；山雀
CLC number: Q959.739:S773.34 Document code: A
Article ID: 1007-662X(2005)04-0301-02

05-04-013
开顶箱内自然气流的湍流统计特性/张军辉，韩士杰，宋国正
（中国科学院沈阳应用生态研究所，沈阳 110016,中国）
//Journal of Forestry Research.–2005, 16(4): 303–305.
开顶箱内细致的湍流交换特性刻画有助于其在外场试
验中的科学应用。本研究（2004 年 5 月份）使用三维超声风
温仪在开顶箱内的高频观测资料细致分析了自然状态下的开
顶箱内部湍流交换主要特征统计量。结果显示，与自然条件