Enhancement of bending properties of Douglas-fir and poplar laminate veneer lumber (LVL) beams with carbon and basalt fibers reinforcement

Abstract

This paper presents the experimental results of the bending mechanical behavior (static and dynamic moduli, and maximum stress) of LVL (Laminated Veneer Lumber) beams reinforced with fiber polymer material (FRP). Different variables were studied: i) Wood species (Douglas fir or poplar); ii) Type of reinforcement (bidirectional carbon, unidirectional carbon or basalt); iii) Veneer quality and iv) Veneers orientation in the beam (flatwise or edgewise). The reinforcement percentages respect to the total cross-section was of 2.17%, 0.89%, and 1.74% for the unidirectional carbon, bidirectional carbon and basalt, respectively. A clear improvement provided by unidirectional carbon has been demonstrated (up to 40% more in the elastic modulus for the flatwise layout and more than 20% of the maximum stress, for both wood species). The influence of the quality of the veneers of the panel was also clearly demonstrated: the weakest wood material obtained the greatest improvements in their mechanical properties when reinforced, allowing to obtain stiff second quality poplar LVL, or strong second quality Douglas fir LVL.