Sandwich compression of wood: control of creating density gradient on lumber thickness and properties of compressed wood

Gao, Zhiqiang; Huang, Rongfeng; Lu, Jianxiong; Chen, Zhangjing; Guo, Fei; Zhan, Tianyi

doi:10.1007/s00226-016-0824-2

Cited by 33 publications

(30 citation statements)

References 9 publications

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“…Additionally, the tested samples had no defects (e.g., knots), which also contributed to developing a constant density distribution. Moreover, the density profile results verified that the density profile of all HPcompressed specimens differed from that of previous hot-pressing compression methods (Kutnar et al 2009;Gao et al 2016). The N-shaped density gradient across the thickness showed the lower density region on both sides and obvious higher plateau region in the middle.…”

Section: Effects Of Hp On Densitysupporting

confidence: 55%

“…This technique resulted in an improvement of the quality of densified wood products. During the past few decades, thermo-hydro-mechanical (THM) compression, thermo-mechanical (TH) compression, viscoelastic thermal compression (VTC), and sandwich compression have been developed (Navi and Heger 2004;Welzbacher et al 2008;Kutnar et al 2009;Fang et al 2012;Gao et al 2016;Laine et al 2016). Navi and Girardet (2000) reported that the mechanical properties of spruce, pine, and beech wood were significantly enhanced by THM treatment, particularly in the shear strength, with the increase rate of more than tenfold.…”

Section: Introductionmentioning

confidence: 99%

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Effects of High-Pressure Treatment on Poplar Wood: Density Profile, Mechanical Properties, Strength Potential Index, and Microstructure

Yu¹,

Zhang²,

Zhu³

et al. 2017

BioResources

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The density profile, mechanical properties, strength potential index, and microstructure changes of hybrid poplar were investigated before and after high-pressure (HP) treatments. The results of density profile indicated that a high uniform density distribution was developed inside the pressurized wood samples. The mechanical properties results showed that the HP treatments significantly increased (P < 0.05) the modulus of elasticity (MOE), the modulus of rupture (MOR), and the Brinell hardness (BH) of the densified wood at selected conditions. Of all the wood samples, the compressed wood at 150 MPa condition possessed the highest density and strength properties. Considering the variation in strength properties along with density, it can be concluded that the compression destruction degree of HP treatment was comparable with that caused by optimized thermal compression technique based on the strength potential index results. The integrity of wood cells presented in scanning electron microscopy results demonstrated the compression of wood cell wall achieved by HP treatment without causing any fractures, which further indicated that HP treatment is a less destructive compression technology. Based on this research, HP treatment has great potential to be applied in wood densification for commercial use.

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Section: Effects Of Hp On Densitysupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Effects of High-Pressure Treatment on Poplar Wood: Density Profile, Mechanical Properties, Strength Potential Index, and Microstructure

Yu¹,

Zhang²,

Zhu³

et al. 2017

BioResources

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show abstract

“…This method could give compressed wood homogenous density, and avoid unfavorable density gradient effect. In contrast, density gradient effect is typical for common methods, which higher density is generated near the surface and lower toward the center of board (Gao et al 2016;Laine et al 2016). These may be related to the much higher pressure levels used in HP treatment.…”

Section: Densificationmentioning

confidence: 99%

“…These may be related to the much higher pressure levels used in HP treatment. Gao et al (2016) employed a sandwich compression of wood with 6 MPa pressure, which is far less than the lowest pressure level (50 MPa) used in this study. Another distinct advantage of using HP compaction as used in this study is the relatively short processing time (5 min) as compared with long compaction processing times (0.5 to 5 h) in traditional methods (Morsing 2000;Kamke 2006;Kutnar and Kamke 2012;Gao et al 2016;Laine et al 2016).…”

Section: Densificationmentioning

confidence: 99%

“…He et al (2008) and Kutmar and Kamke (2012) have used this method to obtain compression wood after a softening treatment, and the modulus of rupture (MOR) and the modulus of elasticity (MOE) of compressed wood increased by 20% and 62% at the compression ratio of 50%. Gao et al (2016) developed this method by adjusting the moisture and temperature distributions within the lumber. Using this developed method, the MOE and MOR values of compressed poplar wood could be increased by 73.2% and 88.9% at the compression ratio of 47%.…”

Section: Introductionmentioning

confidence: 99%

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High-Pressure Treatment of Chinese Fir Wood: Effect on Density, Mechanical Properties, Humidity-Related Moisture Migration, and Dimensional Stability

Li¹,

Zhang²,

Ramaswamy³

et al. 2016

BioResources

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A new densification technique for industrial uses of plantation wood was studied. Chinese fir wood was treated by high pressure (HP) at 50 to 200 MPa for 5 min. The density and mechanical properties, moisture sorption isotherm (MSI), and dimensional changes of the pressure-treated wood under various relative humidity (RH) storage conditions were evaluated. The densities of HP-treated wood ranged from 0.79 ± 0.01 g/cm 3 after treatment at 50 MPa to 0.92 ± 0.02 g/cm 3 at 200 MPa, which was significantly higher (p < 0.05) than that of the control (0.35 ± 0.01 g/cm 3 ). Hardness values in radial and tangential fiber alignment faces also significantly increased by 370% to 470% and 350% to 460%, respectively, as compared with the control. The modulus of elasticity and the modulus of rupture of pressure-treated wood increased by 48% to 88% and 89% to 170%, respectively. The equilibrium moisture content varied with RH, decreasing slightly at 33% and 52% while significantly increasing (p < 0.001) at 86% and 93% RH. Radial, tangential, and volumetric dimensions of densified wood were relatively stable at 33%, 52%, and 67% RH, while remarkable swelling occurred at 86% and 93% RH.

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Forming, Densification and Molding

Sandberg

Eggert²,

Haider

et al. 2023

Springer Handbooks

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Sandwich compression of wood: control of creating density gradient on lumber thickness and properties of compressed wood

Cited by 33 publications

References 9 publications

Effects of High-Pressure Treatment on Poplar Wood: Density Profile, Mechanical Properties, Strength Potential Index, and Microstructure

Effects of High-Pressure Treatment on Poplar Wood: Density Profile, Mechanical Properties, Strength Potential Index, and Microstructure

High-Pressure Treatment of Chinese Fir Wood: Effect on Density, Mechanical Properties, Humidity-Related Moisture Migration, and Dimensional Stability

Forming, Densification and Molding

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