Finger-jointing Technics And Performance Prediction Of Four Species Of Eucalyptus Plantation

E.exserta, E.citriodora, E.grandis and E.urophylla×grandis as experiment materials, PVAc and API as adhesive, the research focused on the optimal processing parameters, and investigated the effects of density, finger type, adhesive etc on the finger-jointing properties, and simply predicted the changing rule through 3 NDT methods before and after finger joint. Optimal processing parameters: (1) Feed speed is one of the most important factors of roughness of finger surface and precision of finger pitch. Generally, faster feed speed can cause poorer finger quality. Because the densities of the 4 eucalyptus species are much different, the optimal feed speed of high density of E.exserta and E.citriodora is 5 m/min. the optimal feed speed of lower density of E.grandis and E.urophylla×grandis is 10 m/min. (2) Adhesion is an important step in the processing of finger-joint. The products quality and performance are affected by adhesion. Spreading of finger-jointing is fitable when finger surface is coated with even gluelines. And different adhesive has different strength. API performs a better strength than PVAc. Effects on finger-jointing performances: (1) Embedment is a guarantee to make the force act on the finger surface. Under 3 levels, finger-jointing with 0.1 mm embedment is the best, which has the highest strength and best appearance quality. (2) End-pressure has been proven to be the most critical variable determining joint strength. When embedment epuals to 0.1mm, with PVAc by hand, the optimal end-pressure of E.exserta, E.citriodora, E.grandis and E.urophylla×grandis is 10 kN, 10 kN, 10 kN, 11.5 kN, respectively. (3) Selection of finger type is determined by purpose and strength. The research results show that vertical finger-jointing has the same performance as horizontal finger-jointing. But, at the same processing conditions, horizontal finger type can bear the bigger end-pressure. Prediction by NDT: The dynamic MOE was measured using the ultrasonic, stress wave and FFT before and after finger joint, the results show that the dynamic MOE's linear relation with mechanical MOE is higher than density's linear relation with mechanical MOE. So the 3 NDT methods can take place of density as means to classify for wood panels.