Predictive expressions for withdrawal force capacity of various size of dowels from particleboard and medium density fiberboard

The objective of this study was to develop predictive expressions for estimating the withdrawal force capacity of various size of beech ( Fagus orientalis ) dowels from medium density fiberboard (MDF) and parti cleboard (PB). Furthermore, effects of the base material type, dowel diameter, dowel penetration and adhesive type on withdrawal force capacity were investigated. Polyurethane (PU), polyvinyl acetate based D2, and polyvinyl acetate (PVA) adhesives were utilized for gluing of dowels. A total of 540 specimens were prepared for edge and face withdrawal force capacity tests including two material types (MDF, PB), three dowel diameters (6 mm, 8 mm, 10 mm), three dowel penetration depths (15 mm, 20 mm, 25 mm for edge, 6 mm, 9 mm, 12 mm for face), three adhesive types and five replications for each group. Specimens were tested under static withdrawal forces. Based on results of tests, predictive expressions that allow furniture engineers to es timate edge and face dowel withdrawal force capacity as a function of dowel diameter and dowel penetration were developed. Calculations showed that the expressions developed provided reasonable estimates for withdrawal force capacity of dowels. As a result of statistical analyses, material type, dowel diameter, dowel pene -tration, adhesive type and their four-way interaction have significantly affected the withdrawal force capacity of dowels. Test results also indicated that PU adhesive and MDF ranked the highest withdrawal force capacity among the adhesive and material types. Increasing either dowel diameter or penetration tended to have a positive effect on withdrawal force capacity. Dowel diameter was found to have a higher effect on withdrawal force capacity than dowel penetration. orientalis ), bonded parallel and vertical to the surface of MDF and PB with polyvinylacetate (PVAc) and Polyurethane (PU) adhesives. They obtained the highest withdrawal strength in beech dowels bonded ver-tically with PVAc adhesive to the surface of MDF at 7,91 MPa. Uysal and Kurt (2007) investigated the effects of edge banding thickness, dowel dimension, type of material and type of adhesive used for edge banding on the withdrawal strength of dowel. Results showed that the highest withdrawal strength (7,019 MPa) was obtained in beech dowels with 6 mm diameter for MDF with solid wood edge banding of white oak with 10 mm thickness bonded with the hot-melt adhesive. In a similar study carried out by Yapıcı et al . (2011), it was determined that the edge banding thickness, dimension of dowels, material type. and adhesive type used for edge banding have significant effect on withdrawal strength of dowels. They obtained the highest withdrawal strength in beech dowels (6,68 MPa) with 8 mm diameter for MDF with 5 mm thickness of solid wood edge banding of bonded beech with PU adhesive. Kurt et al . (2009), determined the withdrawal strengths of 6 mm, 8 mm, 10 mm diameter beech dowels with respect to edge of MDF or PB edged with 5 mm, 10 mm and 15