Enhancing the mechanical performance of locally sourced wood-based plywood through hybridization with natural fibre composites
Topic(s) : Material science
Co-authors :
Clément PRUNIER (FRANCE), Thomas JEANNIN , Jérôme ROUSSEAU , Pauline BUTAUD (FRANCE), Vincent PLACET (FRANCE)Abstract :
Reconstituted wood products, such as plywoods, aim to minimize inherent wood variability to improve mechanical properties. Despite efforts, the cross-ply stratification in plywoods does not completely eliminate mechanical variability, thereby limiting their use in weight-sensitive applications. In the transport industry, synthetic materials have replaced wood due to homogeneity concerns. Therefore, tests traditionally done in the transport industry like fatigue tests are rarely performed on plywood. The only studies conducted are those realised before the substitution [1].
Several recent studies have shown that it is possible to improve the properties of plywood by reinforcing it with fibre-based composites materials, as mentioned in the recent review study by Castanié et al.[2].
The aim of this work is therefore to investigate the quasi-static and fatigue behaviour of plywood manufactured using locally sourced low-quality veneers, thermoplastic matrix as an adhesive and reinforced with long plant fibres.
The studied plywoods consist of five plies manufactured of either Douglas fir or beech veneers, each ply being 3 mm and 2 mm thick, respectively. The Douglas fir veneers are categorized as “low quality” veneers due to the presence of knots, cracks, and variable grain orientation. The plywoods made with beech veneers, which are of higher quality, serve as a reference. The veneers are arranged in a 0-90-0-90-0 stratification for unreinforced plywoods, with 0° representing the wood grain direction. For reinforced plywoods, 5 flax plies are placed after the first and before the last veneer, as shown in Fig. 1 (a)), . The prevalent formaldehyde-based adhesives in the plywood industry are being replaced with eco-friendly and non-toxic alternatives. Tested adhesives include recycled polypropylene (rPP) resin grafted with maleic anhydride (MA) for natural surface compatibility (rMAPP), and a polylactic-acid (PLA) based resin. Fibre reinforcement is provided by unidirectional long flax fibres (FlaxTape®). The plywoods are assembled by thermocompression using an optimised fabrication cycle. All plywoods are tested in three-point bending according to the EN310 standard (Fig. 1 (b)), and in tensile testing according to the EN789 standard.
The results of these quasi-static tests are used as a reference to define the loading levels in the fatigue tests, which are based on the three-point bending tests presented in the EN310 standard. The loading frequency is fixed at 5 Hz in order to limit the change in properties that may be caused by self-heating. The fatigue tests are stress controlled using different stress levels which are percentages of the maximal quasi-static stress value. The study of fatigue tests involves monitoring the evolution of the plywood's bending modulus and damage variables. The effect of the flax fibre reinforcement on these parameters is assessed, providing an insight into the suitability of the material for transport applications.
Several recent studies have shown that it is possible to improve the properties of plywood by reinforcing it with fibre-based composites materials, as mentioned in the recent review study by Castanié et al.[2].
The aim of this work is therefore to investigate the quasi-static and fatigue behaviour of plywood manufactured using locally sourced low-quality veneers, thermoplastic matrix as an adhesive and reinforced with long plant fibres.
The studied plywoods consist of five plies manufactured of either Douglas fir or beech veneers, each ply being 3 mm and 2 mm thick, respectively. The Douglas fir veneers are categorized as “low quality” veneers due to the presence of knots, cracks, and variable grain orientation. The plywoods made with beech veneers, which are of higher quality, serve as a reference. The veneers are arranged in a 0-90-0-90-0 stratification for unreinforced plywoods, with 0° representing the wood grain direction. For reinforced plywoods, 5 flax plies are placed after the first and before the last veneer, as shown in Fig. 1 (a)), . The prevalent formaldehyde-based adhesives in the plywood industry are being replaced with eco-friendly and non-toxic alternatives. Tested adhesives include recycled polypropylene (rPP) resin grafted with maleic anhydride (MA) for natural surface compatibility (rMAPP), and a polylactic-acid (PLA) based resin. Fibre reinforcement is provided by unidirectional long flax fibres (FlaxTape®). The plywoods are assembled by thermocompression using an optimised fabrication cycle. All plywoods are tested in three-point bending according to the EN310 standard (Fig. 1 (b)), and in tensile testing according to the EN789 standard.
The results of these quasi-static tests are used as a reference to define the loading levels in the fatigue tests, which are based on the three-point bending tests presented in the EN310 standard. The loading frequency is fixed at 5 Hz in order to limit the change in properties that may be caused by self-heating. The fatigue tests are stress controlled using different stress levels which are percentages of the maximal quasi-static stress value. The study of fatigue tests involves monitoring the evolution of the plywood's bending modulus and damage variables. The effect of the flax fibre reinforcement on these parameters is assessed, providing an insight into the suitability of the material for transport applications.