Structural Properties Of Glass Fibre Reinforced Cylindrical Laminated Veneer Lumber

Cylindrical laminated veneer lumber (cylindrical LVL) is a newly developed engineered structural material. Developing this material fits for the requirement of economic continual development in our country. Cylindrical LVL can use low-quality materials such as shorter wood veneers as raw material, so it makes use of wood more effectively. Thus, developing this new product can help minimize the conflict between supply and demand for wood material. On the other hand, hollow cylindrical LVL also has many advantages compared to wood log, such as light-weight, high bending strength, and uniform structural performance. Therefore it is highly important to develop this new product using low-quality fast-growing species in our country.In this study, cylindrical LVL was manufactured from poplar and birch veneers using API and IC resin adhesives. In order to improve the structural performances of cylindrical LVL, glass fibre was used as reinforced material. The effects of addition layers of glass fiber, wood species, and resin types on the properties of cylindrical LVL were discussed. The moisture sorption property, dimension stability, bending strength, compressing strength, and elastic modulus were evaluated.In order to investigate the suitable wind angle of cylindrical LVL, we measured and analysed the LVL's tensile elastic modulus through experimental and theoretical methods. The result showed that the tensile elastic modulus decreased with the increase of the angle between the interlocked grains. As the angle was less than 10° the tensile elastic modulus reduced little, while it significantly decresed as angle was bigger than 10°. This indicated that the angle should be less than 10° in the munufacture of cylindrical LVL.A sorption hysteresis was observed for all materials tested. Nelson's sorption isotherm model reproduced accurately the experimental data of glass fiber-reinforced cylindrical LVL.The dimensional stability of cylindrical LVL was evaluated according to ASTM D 1037 of USA standard. It includes thickness swelling (TS), water adsorption (WA) and linear expansion (LE). The results showed that glass fibre had significant influence on TS, WA, and LE. TS, WA, and LE decreased when the layers of glass fibre increased. This show that glass fibre can improve the dimensional stability for cylindrical LVL.The result of bending properties showed that bending strength increased when the addition layers of glass fibre increased, and this increase was different for different species andresins.The results of compressing strength showed that the longitudinal strength was higher than the altitudinal value. Both longitudinal strength and altitudinal strength showed a decreasing trend for non reinforced cylindrical LVL, while the compressing elastic modulus of glass fibre-reinforced cylindrical LVL was significantly improved.