a Poplar (Populus euramericana cv.) is one of the most important fastgrowing tree species in China, but so far its utilization has been limited to nonstructural wood-based panels. The objective of this work was to develop a good understanding of how to improve the mechanical properties of poplar laminated veneer lumber (LVL) with carbon fiber reinforced polymer (CFRP). A theoretical model was successfully developed to predict the bending modulus of elasticity (MOE) of LVL reinforced by CFRP. To validate the model, two different configurations of LVL were made in the laboratory: LVL reinforced with a single layer of CFRP on one side (LVL-SR) and LVL reinforced with a single layer of CFRP on each side (LVL-DR). It was found that the model prediction of the LVL MOE agreed well with the experimental results. LVL reinforced with CFRP had a greater MOE and modulus of rupture (MOR) than the control LVL. The MOE of the LVL-SR and LVL-DR increased by 40% and 67%, respectively.

No abstract

Changbai larch (Larix olgensis Henry) is one of the main plantation species in the northern part of China, but so far its utilization has been limited to solid wood, pulping, and paper products. As part of a national initiative, the objective of this work was to develop a good understanding concerning how stand management practices affect larch wood and veneer properties. To cope with the variation of initial and final stand density, the term "relative thinning intensity (RTI)" was introduced to describe the effect of stand thinning on the resulting wood and veneer properties. Nine representative sample trees each from four stands were harvested, then trimmed and bucked. Six 1.25 m long bolts along the entire tree stem were systematically cut to peel 2.6 mm thick veneers. Clear wood specimens were also sawn from matched bolts for mechanical testing for the purpose of comparison and validation. The correlation between the main tree variables and properties of clear wood and veneer was analyzed, and the influence of RTI on key wood and veneer properties was examined and compared. A good correlation was found in density and modulus of elasticity (MOE) between larch clear wood and veneer, giving an R 2 of 0.75 and 0.71, respectively. This indicates that veneering can be potentially used to characterize this larch species. The stand with the lowest RTI had the shortest rotation but yielded the best properties of both clear wood and veneer, which highlights the importance of stand management in terms of thinning.

No abstract

aThe purpose of this study was to investigate the feasibility of using resonance-based acoustic technologies for sorting Chinese poplar logs for laminated veneer lumber (LVL) products. Representative poplar logs were sampled. Each log was first tested for acoustic velocity and then peeled into veneer. Each veneer sheet was subsequently dried and measured with a production-line veneer tester. LVL beams were made, and their stiffness was non-destructively measured by both time-of-flight (TOF) acoustic method and free-beam vibration methods. Based on the LVL dynamic modulus of elasticity (MOE) values, logs were sorted into several grades with known grade outturns. The results showed that there was a strong correlation between resonance-based acoustic velocities of logs and dynamic MOE of veneer and LVL. Thus, it is feasible to predict the stiffness of LVL products based on log resonance-based acoustic velocity measured. The resonance-based acoustic measurement is easy to use and reliable, which can help increase the grade outturn and in turn value recovery of Chinese poplar logs. It was estimated that the log grade outturns were approximately 31.1% for LVL grade 1, 38.6% for LVL grade 2, and 26.1% for LVL grade 3.