Correlation between Radial Variation and Mechanical Properties of Laminated Veneer Lumber made from 14 Poplar Cultivars

Abstract

France is poplar largest producer in Europe. Most of companies have a very specialized raw material supply chain since they use almost one type of cultivar for their specific products. For example, I-214 is very suitable for light packaging, consider as exclusive raw material in all industries. However, to prevent companies from a potential disease of their unique raw material, we need to find alternative cultivars. 14 cultivars were then characterized in terms of material, mechanic, peeling, wood pulp properties in a collaborative project (CNPF-IDF, FCBA, INRA, ENSAM). As common knowledge, juvenile wood had lower mechanical properties than mature wood. In this research, we gave information about mechanical properties of LVL made from juvenile and supposed mature veneers from 14 poplar cultivars. Its objective was to classified veneer poplar cultivars into two categories: suitable for structural purposes and non-structural purposes. From each cultivars (theirs ages were 13-19 years old), we took two logs, then we peeled into 3 and 5.2 mm thick veneers. We separated veneers that resulted from sapwood and heartwood to produce LVL panels mostly performed with juvenile wood or “more mature” wood. The veneers were glued using polyvinylacetate (PVAC). The boards were then cut into standardized samples (21*21*500 mm) for mechanical tests, i.e. four points bending tests (1280 samples). Before these tests, nondestructive measurements of the MOE have been made on the bending samples using the BING method (vibration tests). The results showed that correlation between destructive and non-destructive test was 0.79 (it means nondestructive test could be used as reference to estimate MOE). Based on non-destructive test, poplar cultivars which were categorized for potential structural purposes, were: Brenta, Lambro, Soligo and Taro. The rest of poplar cultivars (A4A, Alcinde, Dvina, I-214, Koster, Lena, Mella, Polargo, Trichobel and Triplo) were categorized in non-structural. Also we found, there was a significant effect of juvenility for each cultivar . Sample taken from each veneer constituting panels were taken to measure the Micro Fibril Angle. The next step is to analyze the effect of MFA on mechanical characteristics of the panels for different cultivars