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AbstractThermoforming of wood veneers into profiles is a novel idea and the focus of this paper is to study the formability characteristics of thin radiata pine (Pinus radiataD. Don) veneers, which are generally used as surface coverings. Radiata pine is well suited as a raw material for furniture, joinery, and interior architectural products. This is because it has excellent turning, shaping, and laminating properties and readily achieves brilliant stain and paint finishes. In this study, radiata pine veneers were softened by immersion in a hot water bath and then thermoformed by means of heated dies/moulds. The formability characteristics were investigated by conducting single-curvature V-bending tests. The influence of the forming method on the shape conformance of softened veneers under single- and multiple-bend conditions was examined. The paper also discusses the influences of manufacturing parameters that include the softening method, the die temperature, the duration of forming, the ratio of bend radius to veneer thickness, and the veneer architecture. The study clearly establishes the feasibility of forming veneers into multi-bend products in a semi-continuous manner using matched dies. [ABSTRACT FROM AUTHOR]

AbstractRoll forming is a rapid operation that employs consecutive roll stations to progressively deform a strip into a desired profile. The continuous nature of the process coupled with its versatility and speed makes it extremely attractive for producing lightweight, structurally efficient components from sheet materials. This paper describes the roll forming of plywood by heated rolls, which is an innovative concept that can increase the range of usage and add value to the end products. Deformation length measurements from static roll bend tests were carried out to determine the roll spacing and the results agree well with the values predicted by a modified theory based on the minimisation of the total deformation energy for a rigid-plastic material. The deformation lengths, such as in metals and composite sheets, depend essentially on the geometric parameters of the profiles produced and are practically independent of the mechanical properties of the work material. Further, the real-time strain measurements by strain gauges bonded on the roll formed specimens show that the strain profiles compare reasonably well with those obtained for metallic and continuous fibre-reinforced thermoplastic sheets. Finally, the macroscopic deformation of veneer sheets due to roll forming has been analysed kinematically by means of grid strain analysis and the geometric conformance of the product has been determined. [ABSTRACT FROM AUTHOR]

To understand the mechanism of bulk wood forming, compressive stress relaxation experiments were performed on radiata pine (Pinus radiata D. Don) specimens with various moisture contents at a temperature of 200°C. The results aided in understanding the time-dependent viscoelastic behaviour with respect to springback and microstructural changes. This study clearly demonstrates the commercial feasibility of value-adding applications such as pattern forming on wood panels using a relatively simple, quick and inexpensive procedure. The experimental data were characterised by a three-component model with a spring and a Maxwell element in parallel, which showed very good agreement under different forming conditions. [ABSTRACT FROM AUTHOR]

For many applications, the perceived quality of a medium-density fibreboard (MDF) is influenced by the appearance of its machined surface. The behaviour of MDF has been studied by passing a cutting tool through it at a relatively low speed. A digital camera was used that travels synchronously with the tool and the deformation occurring in front of the tool tip was recorded. The magnification of approximately 30× also allows the individual fibres or bundles to be clearly observed. Photographic images have also been taken of the same machining process at a much higher speed, producing similar results and thus establishing the slow-speed study as a viable option. The machining of different MDF samples has been recorded using a cutting speed of 1.6 mm s−1 and varying depths of cut (0.5, 0.75 and 1.0 mm). The video recordings of various panels permit the identification of their peculiar machining characteristics. Unrefined particles play a major role during machining. The trends of results have also been confirmed by scanning electron micrographs. The board densities were found to have a major influence on the machinability characteristics of the boards. [ABSTRACT FROM AUTHOR]

Melt blends of poly (butylene terephthalate) (PBT) and poly (ethylene naphthalate) (PEN) with 30, 40, 50, 60 and 70 wt% PEN were prepared using a single screw extruder and injection moulding machine. 13C and 1H nuclear magnetic resonance (NMR) spectra were obtained with a Bruker DRX-400 instrument, on solutions prepared by dissolving samples of the homopolymers and each blend in deuterated trifluoroacetic acid + chloroform mixtures (1:1 by volume). The absence of new signals in 1H and 13C spectra, that would be expected to result from transesterification reactions in the PBT + PEN blend system, provides convincing evidence that such reactions do not occur in these blends under the melt processing conditions that were used. In the light of published work on solid-state NMR studies of these and related blend systems, and our observations of partial miscibility with a very small domain size, together with substantial enhancement of the mechanical properties of PBT by blending with PEN, we conclude that the improvement in mechanical properties arises from molecular scale mixing of the homopolymers and strong but non-covalent bonding interactions over the very large interfacial area between the PBT-rich and PEN-rich phases. [ABSTRACT FROM AUTHOR]