Flax Fiber-Reinforced Glued-Laminated Timber in Tension Perpendicular to the Grain: Experimental Study and Probabilistic Analysis

Journal article, 2010

The weak mechanical properties of wood in tension perpendicular to the grain are often the origin of catastrophic brittle failure. In order to enhance the tension strength perpendicular to the grain and achieve a more ductile failure, flax fiber and glass fiber-reinforced polymer FRP composites were used to strengthen glue-laminated glulam timber specimens. Three series of specimen of glulam timber flax fiber reinforced, glass fiber reinforced, and unreinforced, with a grand total of 28 specimens, were tested in tension perpendicular to the grain. For an approximate amount of FRP reinforcement of 1.2% in volume thickness of 0.7 mm, an increase of the tensile strength of up to 74% was shown, with a stiffness increase of up to 41%. For all reinforced specimens, semiductile failures were observed. A parametric study was carried out using both the Monte Carlo MC method and the first-order second moment FOSM method. It is shown that the mean values obtained during experiments are in agreement with those from the MC simulation. However, the standard deviations from the MC simulation are larger. From the FOSM analysis, it is demonstrated that the variation in glulam stiffness perpendicular to the grain is not the first parameter driving the variation for the reinforced system. The variation in mechanical properties of the flax fibers appeared to be the driving parameter for the strength of the system.