Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Vaziri, Mojgan; Lindgren, Owe; Pizzi, A.

doi:10.1163/016942410x525713

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…Several studies reported the ability of lignocellulose from wood or annual plants to be assembled/ bonded without adhesive by static methods like thermo-compression, possibly assisted by injection of steam [7,8] or by dynamic processes like vibrational welding at low frequency [9][10][11][12][13][14] or ultrasonic compression [15].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic welding of 100% lignocellulosic papers

et al. 2019

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Paper-based packaging materials are generally assembled using adhesives formulated with oil-based polymers. These adhesives make the recyclability of the materials more complex and may be the source of material contamination by mineral oil. In view of developing an adhesive-free process, the potential of ultrasonic compression was investigated in this study. 100% lignocellulosic papers were assembled using an ultrasonic welder dedicated to thermoplastic polymers. For papers containing lignin, the measured peeling strengths were equivalent to those achieved by hot-melt gluing, provided that the water content of papers was well adjusted. At the interface between bonded papers, the fiber network was dense and rather continuous. SEM examinations, 3D X-ray microtomography images, and temperature measurements suggested that the development of adhesion originated to a large extent from a thermoplastic welding mechanism: wood fiber polymers passed their glass transition temperatures, creeped and formed a matrix that coated fibers. Thus, ultrasonic welding appears as an efficient adhesive-free technique for assembling papers that are used in a broad range of packaging applications.

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Section: Introductionmentioning

confidence: 99%

Ultrasonic welding of 100% lignocellulosic papers

et al. 2019

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“…This is reflected in the WFP, which yielded a higher share as the tensile-shear strength increased. As mentioned by Vaziri et al (2011), examination of the tensile-shear strengths reveal that adhesion in the welded joint is a function of welding time and most probably passes through various characteristic phases. Similar behaviour occurred in the present study, i.e., the strength improved with increased welding time before encountering a drop after a certain point in time (3.5 s).…”

Section: Resultsmentioning

confidence: 88%

“…The thickness of the welded zone also varies as a function of the maximum temperature reached during welding, whilst the maximum temperature reached at the ends of the specimen has been found to be lower than that in the central part of the specimen (Ganne-Chedeville et al 2006). According to Vaziri et al (2011), the degree of densification at the weld line varies from 160 to 190% of the untreated wood density. According to Properzi et al (2005), bond line strength is influenced by the orientation of the wood grain on the two bonding surfaces.…”

Section: Introductionmentioning

confidence: 99%

Influence of Welding Time on Tensile-Shear Strength of Linear Friction Welded Birch (Betula pendula L.) Wood

Ruponen¹,

Čermák²,

Rhême³

et al. 2015

BioResources

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aThe purpose of this work was to determine the optimal welding time for linear friction welding of birch (Betula pendula L.) wood while keeping the other parameters constant and at similar levels compared to other species in a similar density range. Specimens with dimensions of 20 × 5 × 150 mm 3 were welded together, and the influence of welding time (2.5, 3.0, 3.5, and 4.0 s) on the mechanical properties of the specimens was determined. The studies included a tensile-shear strength test as well as visual estimation of wood failure percentage (WFP). Additionally, X-ray microtomographic imaging was used to investigate and characterise the bond line properties as a non-destructive testing method. The highest mean tensile-shear strength, 7.9 MPa, was reached with a welding time of 3.5 s. Generally, all four result groups showed high, yet decreasing proportional standard deviations as the welding time increased. X-ray microtomographic images and analysis express the heterogeneity of the weld line clearly as well. According to the averaged group-wise results, WFP and tensile-shear strength correlated positively with an R 2 of 0.93. An extrapolation of WFP to 65% totals a tensile-shear strength of 10.6 MPa, corresponding to four common adhesive bonds determined for beech.

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“…The degree of densification of weld lines (weld line density divided by the non-welded wood density) for the heartwood specimens was lower than that for the sapwood samples of Scots pine. Furthermore, the water-resistance of weld lines seemed to be independent of the density of weld lines (Vaziri et al 2011b), which is usually twice the density of the wood pieces welded (Ruponen et al 2015).…”

Section: Effect Of Welding Timementioning

confidence: 99%

Adhesiveless bonding of wood – A review with a focus on wood welding

Gedara

Chianella

Endrino

et al. 2021

BioRes

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Most industrially used synthetic wood adhesives release formaldehyde, which is carcinogenic for humans. Adhesiveless bonding of wood can be achieved using heat treatment by either hot-pressing method, suitable mainly for wood particles and fibres or by wood welding. Welding of wood, which relies on the heat generated via friction, can be used for bonding two or more solid wood pieces together. The process can be carried out either by linear or rotational wood welding. This review first considers the manufacturing of binderless wood-based panels by hot-pressing. Then this is followed by an in-depth outlook of wood welding and its application in the wood industry. The effects of varying wood welding parameters, such as applied pressure, vibrational frequency and amplitude, holding pressure, holding time, welding time in linear wood welding, and relative diameter difference between the substrate and the dowel in rotational wood welding to obtain joints with optimal mechanical and physical properties is reviewed and discussed. Wood products made by heat treatment (hot-pressing and wood welding) are environmentally friendly, and the brief curing times needed for their manufacture represent a great advantage compared with the usage of wood adhesives to bind pieces of wood.

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Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Cited by 9 publications

References 14 publications

Ultrasonic welding of 100% lignocellulosic papers

Ultrasonic welding of 100% lignocellulosic papers

Influence of Welding Time on Tensile-Shear Strength of Linear Friction Welded Birch (Betula pendula L.) Wood

Adhesiveless bonding of wood – A review with a focus on wood welding

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