Mechanical Properties of Cellulose and Flax Fiber Unidirectional Reinforced Plywood

This research presents the influence of two different cellulose (hydrophobic pretreated/non-pretreated) and one flax-fiber unidirectional nonwoven low areal weight fiber reinforcements on the mechanical properties of urea-formaldehyde bonded five layered beech (Fagus sylvatica L.) plywood as an alternative to commonly used synthetic fiber reinforcements. The results display divergent trends regarding the improvement of the mechanical properties-modulus of elasticity, modulus of rupture, tensile strength, shear strength, and screw withdrawal resistance. The non-treated cellulose and flax reinforcing nonwoven fabrics revealed similar mechanical behaviors. The hydrophobic pretreatment of cellulose nonwovens improved the performance of plywood regarding tensile strength (10-11%), shear strength (7-16%), screw withdrawal resistance (11-15%), and modulus of rupture (0-2%), but lowered modulus of elasticity (2-3%) compared to the reference.