Knowledge and quality of Laminated Veneer Lumber (LVL)
Laminated veneer lumber (LVL) is a kind of high strength structural material, which is made of veneer by rotary cutting. It is composed of billets in order along the grain direction, oblique joint at the end, lap joint or docking, and then pressed by gluing and hot pressing. Its flexural strength is 18 MPa, shear strength is 1.7 MPa, and elastic modulus is 10 000 MPa. VL has the characteristics of uniform engineering performance and flexible specifications. It is superior to reality. Volume wood, especially suitable for large-span wood structures, VL is especially favored by plywood manufacturers and veneer manufacturers, and its consumption is expected to increase steadily in the future. It can make full use of artificial fast-growing forests and medium and small diameter logs to produce high value-added products.
LVL can be divided into two categories: structural materials (i.e. bearing components) and non-structural materials (i.e. non-bearing components). The original structural material LVL is only used for simple beams, but now it is more and more widely used, such as structural frames, I-beams and other composite products. The main difference between non-structural material LVL and structural material LVL is that it can not be used for load-bearing structures, but only for furniture components, staircase components, doors and windows frames. LVL has a wide range of specifications and thickness. The LVL thickness range of structural materials is mostly 2-5 mm, the maximum thickness can reach 150 mm; the width range is 100-1800 mm; the length range is 2500-25 000 mm, or even infinite length. The dimension of non-structural LVL is usually 5-50mm in thickness, 75-150mm in width and 300-600mm in length. When LVL 4 “X 8” is produced, plywood factories can use most of the existing machinery and equipment to produce LVL products with high efficiency and flexible size with a small amount of investment.
The strength-weight ratio of LVL is better than that of steel. LVL made of parallel grains can reproduce wood anisotropy to the greatest extent. When the structure is stressed, the longitudinal strength of wood can be fully utilized. Because the scars of wood and cracks of veneer are dispersed and evenly distributed in the products, it has uniform mechanical properties. It has the characteristics of uniform quality, stable performance, precise size and uniform straightness that other structural materials can not compare with. It is also easy to process. It can be sawn, planed, cut holes, mortise, nail and so on. After flame retardant treatment, its fire resistance is higher than that of steel. Wood, good weather resistance, and strong earthquake resistance.
Because the laminated structure of LVL greatly reduces the warpage and distortion of products, its size and shape stability is good.
The economy of LVL lies in the use of different wood species and raw materials of different quality for lamination bonding, which achieves the value-added effect of large-scale use of small villages and superior use of inferior timber. It is an effective way to utilize secondary raw materials such as small-diameter timber, curved timber and short logs efficiently. LVL has mature processing technology, simple equipment, low production energy consumption, high yield, low pollution and low production cost. For example, Mingxi County, Fujian Province, is rich in forest resources and produces 110,000 cubic meters of commercial timber annually. Because the production process of LVL is basically similar to that of plywood, LVL production line was reconstructed by wood-based panel factory in this county, which makes full use of the existing idle equipment, improves the utilization ratio of wood, and achieves the combination of forest resources protection and utilization.
LVL has a wide range of applications. It can be used not only in residential and commercial buildings, but also in vehicle materials, shipbuilding materials and sleepers. It can be widely used in various fields, such as load-bearing structures, non-load-bearing structures and furniture frames. When used in residential buildings, it can be widely used in houses, structural frames and floor systems. Because of its high strength-weight ratio, VL is especially suitable for long-span beams and one floor system. Areas where wood and steel cannot simply be replaced. LVL not only retains the ideal natural characteristics of wood, but also has the structural characteristics that solid wood sawing village does not have, and its strength far exceeds that of steel roof truss. Overseas, it is widely used in building roof truss structure, and can be used for floor laying, bowling lane board, container floor, railway sleepers, cement formwork, etc. In recent years, the demand for LVL in Japan and the Middle East has increased dramatically year by year. According to statistics, the global output of LVL in 1998 was 2.3 million cubic meters. It is estimated that the global consumption of LVL will reach 24 million cubic meters by 2002. At present, LVL is produced in North America, Japan, Finland, Australia, New Zealand and other countries. Only Shandong Kailin Wood-based Panel Industry Co., Ltd. is producing LVL in China. Both inside and outside VL materials have good market prospects.
Cutting down natural forests was strictly prohibited in 1998, and the demand for wood-based panels in China increased at an annual rate of 16%. It is expected to reach 35 million cubic meters by 2010. Especially, the demand for wood-based panels and structural panels for construction and decoration is greater, resulting in contradictions between wood raw materials and demand, and the production of wood-based panels can not meet the needs of the market. Fast-growing forest resources can be exploited and utilized within a few years, and architectural design is also in line with international standards. LVL can be produced from small diameter wood, curved wood and short logs with a yield of 60% to 70%. Fast-growing and thinned logs (pine, poplar, etc.) with a diameter of 250mm are more suitable for LVL production. This specification is of great quantity and low price, and it is difficult to produce plywood or wood. It will be feasible to transform existing plywood factories to produce LVL or both, especially in areas where fast-growing and High-yielding forests are well established.
With the deepening of China’s reform and opening up and the entry into WTO, people’s living standards continue to improve, and the demand for wood will continue to increase. In the field of construction, the timber consumption of urban and rural residential construction alone accounts for 20% of the total annual timber consumption in China. According to estimates, the total timber consumption of urban and rural construction in China will reach 85.5 million m by 2010, among which many plywood and its substitutes can be used. In foreign countries, LVL replaces solid wood boards and squares for furniture and architecture has matured, and has the corresponding standard. However, the production and application of LVL in China is just beginning or blank. Therefore, introducing advanced technology actively in our country to produce LVL through technological transformation of existing plywood factories not only has broad market prospects, but also can make our plywood industry embark on the road of sustainable development.Knowledge and quality of Laminated Veneer Lumber (LVL),structural materials,non-structural materials, LVL iNSPETION ,LVL manufacturing Process,LVL LVB QC