Comparison of the TL-Shear Strength of Normal and Compression Wood of European Larch

Holzforschung ◽  
2003 ◽  
Vol 57 (4) ◽  
pp. 421-426 ◽  
Author(s):  
W. Gindl ◽  
A. A.Teischinger
Keyword(s):  
Shear Strength ◽  
Compression Wood ◽  
Fracture Behaviour ◽  
Microfibril Angle ◽  
Middle Lamella ◽  
Longitudinal Shear ◽  
Normal Wood ◽  
European Larch ◽  
The Difference ◽  
Scanning Electron

Summary The strength of larch compression wood specimens in longitudinal shear in the radial plane was determined and compared to normal wood. Fracture surfaces were examined with a scanning electron microscope. Compression wood showed higher shear strength than normal wood. The difference persisted after correction of the strength values for density. Scanning electron microscopy revealed clear differences in the pattern of failure in normal wood compared to compression wood. While transwall and intrawall fracture predominate in normal wood, intercell fracture at the middle lamella occurs in compression wood. An explanation of this change in fracture behaviour is proposed in terms of microfibril angle and lignification of the cell wall.

Comparison of Anatomy and Composition Distribution between Normal and Compression Wood of Pinus Bungeana Zucc. Revealed by Microscopic Imaging Techniques

2012 ◽  
Vol 18 (6) ◽  
pp. 1459-1466 ◽  
Author(s):  
Zhiheng Zhang ◽  
Jianfeng Ma ◽  
Zhe Ji ◽  
Feng Xu
Keyword(s):  
Fluorescence Microscopy ◽  
Compression Wood ◽  
Microfibril Angle ◽  
Middle Lamella ◽  
Chemical Imaging ◽  
Raman Microscopy ◽  
Normal Wood ◽  
Confocal Raman Microscopy ◽  
Pinus Bungeana ◽  
Confocal Raman

AbstractThe anatomy and topochemistry in normal and compression wood tracheid cell wall of Pinus bungeana Zucc. were investigated by fluorescence microscopy and confocal Raman microscopy. Using fluorescence microscopy, the severity of compression wood was classed as a mild type for the reason that it did not contain all compression wood features. Chemical imaging by confocal Raman microscopy was used for analyzing the distribution of lignin and cellulose, as well as the functional groups of lignin in tracheid cell walls. By comparison with normal wood, highly lignified outer S2 layer [S2(L)], thicker S1 layer, and obviously reduced lignification in the middle lamella were characteristic of compression wood. In addition, smaller microfibril angle was observed in the S2(L) region. The distribution of coniferyl alcohol and coniferyl aldehyde in normal and compression wood was enriched in S1 and S2 layers but lack in cell corner and/or S2L regions, which showed an opposite pattern to lignin distribution. Confocal Raman microscopy with high spatial resolution contributes to a further understanding of the differences between normal and compression wood in polymers distribution and molecules orientation in situ.

MICROFIBRIL ANGLE OF THE S1 CELL WALL LAYER OF NORWAY SPRUCE COMPRESSION WOOD TRACHEIDS

IAWA Journal ◽  
2004 ◽  
Vol 25 (4) ◽  
pp. 415-423 ◽  
Author(s):  
Jonas Brändström
Keyword(s):  
Norway Spruce ◽  
Compression Wood ◽  
Microfibril Angle ◽  
Soft Rot ◽  
Wall Layer ◽  
Thermomechanical Pulp ◽  
Ultrastructural Organization ◽  
Normal Wood ◽  
Cell Wall Layer ◽  
Fracture Characteristics

The ultrastructural organization of the outer layer of the secondary wall (i.e. S1 layer) of Norway spruce (Picea abies (L.) Karst.) compression wood tracheids was investigated with emphasis on the microfibril angle. Light microscopy was used to study the orientation of soft rot cavities (viz. microfibril angle) in compression wood tracheids from macerated soft rot degraded wood blocks. In addition, surface and fracture characteristics of compression wood tracheids selected from a thermomechanical pulp were investigated using scanning electron microscopy (SEM). Results showed that the orientation of soft rot cavities varied little between tracheids and the angles were also consistent along the length of individual tracheids. The average S1 microfibril angle in two selected annual rings was 90.0° ± 2.7° and 88.9° ± 2.4° respectively. SEM observations of the compression wood tracheids from the pulp showed distinct fractures between S1 and S2 or within S1 and these fractures were oriented perpendicular to the tracheid axis. It was concluded that the microfibril angle of the S1 layer of compression wood tracheids is higher and less variable than normal wood tracheids. This is considered an adaptation for restraining the compressive forces that act on leaning conifer stems or branches.

Contribution of lignin to the stress transfer in compression wood viewed by tensile FTIR loading

Holzforschung ◽  
2020 ◽  
Vol 74 (5) ◽  
pp. 459-467 ◽  
Author(s):  
Hui Peng ◽  
Lennart Salmén ◽  
Jiali Jiang ◽  
Jianxiong Lu
Keyword(s):  
Compression Wood ◽  
Microfibril Angle ◽  
Stress Transfer ◽  
Direct Coupling ◽  
Normal Wood ◽  
Static Tensile Loading ◽  
Static Tensile ◽  
Lower Load ◽  
Dynamic Loading Conditions ◽  
Molecular Deformation

AbstractTo achieve efficient utilization of compression wood (CW), a deeper insight into the molecular interactions is necessary. In particular, the role of lignin in the wood needs to be better understood, especially concerning how lignin contributes to its mechanical properties. For this reason, the properties of CW and normal wood (NW) from Chinese fir (Cunninghamia lanceolata) have been studied on a molecular scale by means of polarized Fourier transform infrared (FTIR) spectroscopy, under both static and dynamic loading conditions. Under static tensile loading, only molecular deformations of cellulose were observed in both CW and NW. No participation of lignin could be detected. In relation to the macroscopic strain, the molecular deformation of the cellulose C-O-C bond was greater in NW than in CW as a reflection of the higher microfibril angle and the lower load taken up by CW. Under dynamic deformation, a larger contribution of the lignin to stress transfer was detected in CW; the molecular deformation of the lignin being highly related to the amplitude of the applied stress. Correlation analysis indicated that there was a direct coupling between lignin and cellulose in CW, but there was no evidence of such a direct coupling in NW.

Helical Thickenings in Normal and Compression Wood of Some Softwoods

IAWA Journal ◽  
1985 ◽  
Vol 6 (2) ◽  
pp. 131-138 ◽  
Author(s):  
Nobuo Yoshizawa ◽  
Takao Itoh ◽  
Ken Shimaji
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Wall ◽  
Compression Wood ◽  
Normal Wood ◽  
Additional Layer ◽  
Innermost Layer ◽  
Inner Surface ◽  
Helical Thickenings ◽  
Scanning Electron

Compression wood in some softwoods having helical thickenings on the inner surface of normal wood tracheids were examined using a scanning electron microscope. Helical thickenings of Taxus, Torreya and Cephalotaxus have narrow bases, and are loosely attached to the innermost layer of the secondary wall, while those of Pseudotsuga, Picea and Larix have broad bases blended tightly with the microfibrils of the S3 layer in normal wood. The transition from normal to compression wood entails a preservation of the thickenings in Taxus, Torreya and Cephalotaxus, while they are replaced by helical ridges and cavities in Pseudotsuga, Picea and Larix. The direction of helical thickenings gradually changes from an S- to a Z-helix, or a Z- to an S-helix in the course of the transition from normal to compression wood, or vice versa in Taxus, Torreya and Cephalotaxus. Helical checks never occur in these species. In Pseudotsuga, however, helical thickenings can be deposited as an additional layer on the helical ridges. The results obtained in the present investigation revealed that the orientation of the thickenings did not always coincide with that of the innermost microfibrils of the secondary wall layers, indicating that helical thickenings may be considered as a layer independent of the secondary wall.

Lignin distribution in mild compression wood of Pinus radiata

1999 ◽  
Vol 77 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Lloyd A Donaldson ◽  
Adya P Singh ◽  
Arata Yoshinaga ◽  
Keiji Takabe
Keyword(s):  
Cell Wall ◽  
Fluorescence Microscopy ◽  
Pinus Radiata ◽  
Compression Wood ◽  
Middle Lamella ◽  
Confocal Fluorescence Microscopy ◽  
Interference Microscopy ◽  
Normal Wood ◽  
Lignin Distribution ◽  
Confocal Fluorescence

Lignin distribution in the tracheid cell wall of mild compression wood in Pinus radiata D. Don was examined by interference microscopy, confocal fluorescence microscopy, and ultraviolet (UV) microscopy. Two anatomically different samples of mild compression wood were compared with a sample of normal wood using quantitative interference microscopy and microdensitometry combined with confocal fluorescence microscopy to estimate the quantitative or semiquantitative lignin distribution in the S2 and S2L regions of the secondary cell wall and of the cell corner middle lamella (CCML). One of these samples was briefly examined by UV microscopy for comparison. Quantitative interference microscopy provided information on lignin concentration in different regions of the cell wall with values of 26, 46, and 57%, respectively, for the S2, S2L, and CCML regions of sample 1 and 20, 29, and 46%, respectively, for the same regions of sample 2. Microdensitometry of confocal fluorescence images provided semiquantitative information on the relative lignin distribution based on lignin autofluorescence. Comparison between the two compression wood samples using autofluorescence gave results that were in partial agreement with interference microscopy with respect to the relative lignification levels in the S2, S2L, and CCML regions. Some improvement was achieved by using calibration values for hemicellulose rather than holocellulose for interference data in the S2L region. Results for UV microscopy performed on sample 1 indicated that the lignification of the CCML region was comparable with that of the S2L region in this sample but with some variation among cells. All three techniques indicated significant variation in lignification levels of the S2L and CCML regions among adjacent cells and a significant reduction in the lignification of the CCML region compared to normal wood.Key words: lignin distribution, interference microscopy; confocal fluorescence microscopy, UV microscopy, mild compression wood, Pinus radiata D. Don.

Hygrothermal recovery of compression wood in relation to DMSO swelling and drying shrinkage

Holzforschung ◽  
2020 ◽  
Vol 74 (8) ◽  
pp. 789-797
Author(s):  
Shuoye Chen ◽  
Miyuki Matsuo-Ueda ◽  
Masato Yoshida ◽  
Hiroyuki Yamamoto
Keyword(s):  
Compression Wood ◽  
Wood Specimen ◽  
Microfibril Angle ◽  
Drying Shrinkage ◽  
Growth Stress ◽  
Normal Wood ◽  
Dimensional Changes ◽  
The Matrix ◽  
Dmso Treatment ◽  
Hygrothermal Treatment

AbstractTo understand the irreversible dimensional changes caused by hygrothermal treatment of green wood, i.e. hygrothermal recovery (HTR), green hinoki compression wood (CW) and normal wood (NW) were hygrothermally (HT) treated in water at 100°C for 120 min and their HTR strains were determined. The specimens were then swollen using dimethyl sulfoxide (DMSO) and then completely dried after solvent exchange with water at room temperature. Their HTR strains were then compared with their DMSO swelling and drying shrinkage strains. The volumetric HTR strains in the CW were about twice as large as those in the NW. Moreover, the microfibril angle (MFA) was found to be an important factor for controlling the HTR intensity. A clear commonality between the HTR behavior and both DMSO swelling and drying shrinkage behavior was identified, which indicates that HTR is caused by volumetric changes in the matrix substances. HTR has been defined as a phenomenon due to the release of locked-in growth stress when a wood specimen is HT treated. To determine whether DMSO treatment has a similar effect as hygrothermal treatment, both HT-untreated and HT-treated specimens were swollen using DMSO, and their dimensional changes during and after DMSO treatment were compared. The results showed that DMSO treatment is a possible alternative for releasing the locked-in growth stress.

WITHIN-TREE VARIATION IN ANATOMICAL PROPERTIES OF COMPRESSION WOOD IN RADIATA PINE

IAWA Journal ◽  
2004 ◽  
Vol 25 (3) ◽  
pp. 253-271 ◽  
Author(s):  
Lloyd A. Donaldson ◽  
Jenny Grace ◽  
Geoff M. Downes
Keyword(s):  
Wall Thickness ◽  
Compression Wood ◽  
Microfibril Angle ◽  
Basic Density ◽  
Radiata Pine ◽  
Lumen Diameter ◽  
Normal Wood ◽  
Lignin Distribution ◽  
Opposite Wood ◽  
Anatomical Properties

Two trees of radiata pine, one showing severe lean, the other growing almost vertically, were assessed for the presence and anatomical properties of compression wood, including anatomy, lignin distribution, microfibril angle, basic density, radial and tangential lumen diameter and cell wall thickness. Both trees contained significant amounts of compression wood although the severity and amount of compression wood was greater in the leaning tree. Changes in lignin distribution seem to be characteristic of the mildest forms of compression wood with reduced lignification of the middle lamella representing the earliest change observed from normal wood. An increase in microfibril angle was associated with both mild and severe compression wood although examples of severe compression wood with the same or smaller microfibril angles than opposite wood, or with very small microfibril angles, were found. When segregated into mild and severe compression wood the average difference in microfibril angle was 4° and 8° respectively compared with opposite wood. Within-ring distribution of microfibril angle was different in severe compression wood compared to opposite wood with higher angles in the latewood.Severe compression wood showed a 22% increase in basic density compared to mild compression wood and opposite wood. The increased density was accounted for in terms of a 26% increase in tracheid wall thickness throughout the growth ring, offset by a 9% increase in radial lumen diameter, slightly greater in the latewood. There were no significant changes in density or cell dimensions in mild compression wood compared with opposite wood.

Air permeability in longitudinal and radial directions of compression wood of Picea abies L. and tension wood of Fagus sylvatica L.

Holzforschung ◽  
2009 ◽  
Vol 63 (3) ◽  
Author(s):  
Asghar Tarmian ◽  
Patrick Perré
Keyword(s):  
Picea Abies ◽  
Fagus Sylvatica ◽  
Tension Wood ◽  
Compression Wood ◽  
Air Permeability ◽  
Normal Wood ◽  
Reaction Wood ◽  
Anatomical Point ◽  
Bordered Pits ◽  
The Difference

Abstract The air permeability in longitudinal and radial directions of compression wood in spruce (Picea abies) and tension wood in beech (Fagus sylvatica) was compared with that of the corresponding normal wood. The primary aim of the present study was to explain why the reaction woods dry more slowly than the normal woods in the domain of free water. A number of boards conventionally dried to an average final moisture content of 12% were chosen to perform the measurements. Bordered pits on the radial walls of longitudinal tracheids in the compression and normal wood and intervessel or intervascular pits in the tension and normal wood were also examined. The reaction wood of both species is less permeable than the normal wood, both in longitudinal and radial directions. The difference in permeability was more pronounced between compression and normal wood of spruce, especially in longitudinal direction. From an anatomical point of view, this is likely related to some differences in anatomical characteristics affecting the airflow paths, such as the pit features. Such results can explain the difference in drying kinetics of the reaction and normal woods in the capillary regime of drying.

scholarly journals Changes in viscoelastic vibrational properties between compression and normal wood: roles of microfibril angle and of lignin

Holzforschung ◽  
2013 ◽  
Vol 67 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Iris Brémaud ◽  
Julien Ruelle ◽  
Anne Thibaut ◽  
Bernard Thibaut
Keyword(s):  
Cell Wall ◽  
Dynamic Modulus ◽  
Compression Wood ◽  
Microfibril Angle ◽  
Axial Direction ◽  
Vibrational Properties ◽  
Normal Wood ◽  
Time Frequency ◽  
Damping Characteristics ◽  
Frequency Domains

Abstract This study aims at better understanding the respective influences of specific gravity (γ), microfibril angle (MFA), and cell wall matrix polymers on viscoelastic vibrational properties of wood in the axial direction. The wide variations of properties between normal wood (NW) and compression wood (CW) are in focus. Three young bent trees (Picea abies, Pinus sylvestris and Pinus pinaster), which recovered verticality, were sampled. Several observed differences between NW and CW were highly significant in terms of anatomical, physical (γ, shrinkage, CIELab colorimetry), mechanical (compressive strength), and vibrational properties. The specific dynamic modulus of elasticity (E′/γ) decreases with increasing MFA, and Young’s modulus (E′) can be satisfactorily explained by γ and MFA. Apparently, the type of the cell wall polymer matrix is not influential in this regard. The damping coefficient (tanδ) does not depend solely on the MFA of NW and CW. The tanδ – E′/γ relationship evidences that, at equivalent E′/γ, the tanδ of CW is approximately 34% lower than that of NW. This observation is ascribed to the more condensed nature of CW lignins, and this is discussed in the context of previous findings in other hygrothermal and time/frequency domains. It is proposed that the lignin structure and the amount and type of extractives, which are both different in various species, are partly responsible for taxonomy-related damping characteristics.

scholarly journals The difference of Fracture Behaviour between T300 and T800 Quasi-Isotropic Composites

1992 ◽  
Vol 1 (2) ◽  
pp. 096369359200100
Author(s):  
Zen-ichiro Maekawa ◽  
Hiroyuki Hamada ◽  
Tomohiro Kitagawa ◽  
Kueichi Lee
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Tensile Test ◽  
Fracture Behaviour ◽  
Cfrp Laminates ◽  
Fracture Modes ◽  
Reinforcing Fibers ◽  
The Difference ◽  
Scanning Electron

Four types of quasi-isotropic CFRP laminates were tested in this study. Then the fracture behaviours, for example fracture modes and failure processes were observed by microscope and scanning electron microscope after tensile test. As the result, the differences of fracture behaviours between two kinds of reinforcing fibers composites are indicated.

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