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Fir wood flour may be used as filler in glass reinforced composites due to the lower content of tannins in comparison with oak wood flour (Cerbu et al. 2010). This work focuses on the behavior of E-glass / fir wood flour / epoxy hybrid composites in mechanical tests (three-point bending tests, and Charpy impact tests) after immersion in water for 1177, 3048, and 6572 hours. Alternating layers were reinforced either with glass fabric or with fir wood flour. After 3048 hours of immersion, the flexural properties decreased: the modulus of elasticity (MOE) in bending and maximum flexural stress σ decreased by 13.16% and 37.54% respectively, with respect to the values recorded in the case of the dried specimens. The properties recovered a little after saturation because they increased after 6572 hours of immersion: MOE was greater (4.36%), while maximum flexural stress was greater (6.78%) with respect to the values corresponding to the specimens tested after 3048 hours of immersion. In the Charpy test, the impact strength K was measured. The damage (cracks developed at matrix-glass interface) caused by water absorption is discussed in order to explain the degradation of the mechanical properties. The adding of the wood flour led to the increasing of the modulus of rigidity EI in bending and it is proved by comparing with the results obtained in case of glass / epoxy composite without wood flour. Components for outdoor furniture (gardens) could be an application of the hybrid composite analyzed in this paper. Brasov, 29 Eroilor Avenue, 500036, Brasov, Romania; b: Department of Wood Processing and Wood Products Design, Faculty of Wood Engineering, Transilvania University of Brasov, 29 Eroilor Avenue, 500036, Brasov, Romania; *Corresponding author: cerbu@unitbv.ro Keywords INTRODUCTIONHybrid composite materials represent a class of composites that may be reinforced with different kinds of materials in the same layer by using hybrid woven fabrics (e.g. carbon / Kevlar fabric). Other hybrid composites are made of different kinds of layers that are reinforced with only one kind of fibers and layers alternate.The E-glass / fir wood flour / epoxy composites analyzed in this paper were from the last class described above because the layers reinforced with glass fibers alternated with the layers reinforced with fir wood flour. Such a hybrid composite should combine the advantages of wood fibers described below within this section (Klyosov 2007) with the advantages of the glass fibers (Cerbu et al. 2009;Zhou et al. 2013;Wang et al. 2014).Wood plastic composites (WPC) are widely used (Klyosov 2007) because the addition of the wood flour to plastics may potentially lead to material cost reductions while mechanical characteristics can be improved. PEER-REVIEWED ARTICLEbioresources.com Cerbu et al. (2016). "Wood/ glass epoxy composite," BioResources 11(4), 8364-8385. 8365Wood species vary across the world according to geographic area. For example, in the temperate zone, common tree species include fir, oak, beech, hornbeam...

The aim of this research was to evaluate the potential of magnesium lignosulfonate as adhesive in particleboard manufacturing. Diphenylmethane diisocyanate (PMDI) between 1% and 3% and glucose (1% of the lignosulfonate content) were added as potential cross-linkers in the adhesive formulations. Mixed beech and spruce wood, 30% beech wood and 70% spruce wood, were employed for the configuration of the panel structure. The density, mechanical properties and formaldehyde emission of single-layer particleboard were investigated. Spectroscopic analysis (FTIR) revealed structural changes brought by oxidation that may indicate depolymerization by the splitting of C-O-C bonds and formation of carbonyl groups. Mechanical properties were improved, and the highest average values were recorded for panels having as adhesives oxidized lignin with cross-linkers as follow: 15 N/mm2 (MOR), 3320 N/mm2 (MOE) and 0.48 N/mm2 (IB). The density profile presented higher values for faces in case of oxidized lignin panels. Changes were observed for oxidized lignin with cross-linker panels wherein the core had higher values. The results showed that the panels manufactured with adhesives composed of oxidized lignosulfonate (20% of the dried wood particles weight) and the addition of PMDI and glucose in various percentages have a positive influence on their formaldehyde release and mechanical properties requested by EN 312 (2004) standard.

Additive manufacturing (AM) is used in many fields and is a method used to replace wood components or wood-jointed furniture components in the furniture industry. Replacing wood joints by 3D printed connectors would be an advantage, considering the fact that during the process of assembling furniture, the execution technology of the joints is difficult, time-consuming, and labor-intensive. Advanced technology of AM applied in furniture manufacturing helps the designers to create new concepts of product design, with no limits of shape, number of joints, color, or size. The diversity of 3D printers and AM technologies provides the selection of materials in relation with the applicability of the 3D printed object. In this respect, the objective of the present research is to design a 3D printed connector to be used for jointing three chair components, namely the leg and two stretchers made from larch (Larix decidua Mill.) wood, and to use reinforced polylactic acid (PLA) fiberglass (20 wt. %) filament for 3D printing this connector using AM with fused filament fabrication (FFF) technology. The design of the connector, the possibility of using this type of material, and the deposition method of filament were investigated in this research. For this purpose, several evaluation methods were applied: microscopic investigation with 50×, 100×, and 200× magnifications, both of the filament and of the 3D printed connector; mechanical testing of corner joint formed with the help of connector between chair leg and the two stretchers; and a microscopic investigation of the connectors’ defects that occurred after applying the compression and tensile loads on the diagonal direction of the L-type joint. The microscopic investigation of the composite filament revealed the agglomerations of glass fibers into the core matrix and areas where the distribution of the reinforcements was poor. The heterogeneous structure of the filament and the defects highlighted in the 3D printed connectors by the microscopic investigation contributed to the mechanical behavior of L-type connecting joints. The bending moments resulting from compression and tensile tests of the 3D printed connectors were compared to the results recorded after testing, under the same conditions, the normal mortise–tenon joint used to assemble the abovementioned chair components. The larch wood strength influenced the mechanical results and the conclusions of the microscopic investigations, as well as the analysis of the broken connectors after testing recommended the change of connector design and filament deposition direction.