Nodal Line Simply Supported Vibration Method For Evaluating The Mechanical Properties Of Full-Size Wood Composite Panels

Full-size wood composite panel is the common commercial panel which size is 2440X1220mm.The most common method to detennine the mechanical properties of a full-size wood composite panel is to conduct static destructive tests on small specimens cut from different parts of a panel Based on the testing results of multiple small specimens,average property values are derived and assigned to a full-size panel.This is a costly and time-consuming process to wood composite manufacturers.A nondestructive method that can rapidly and accurately determine the mechanical properties of full-size panels is necessary and enable manufacturers to better control the manufacturing process and ensure the final products meeting the required specificationsThis study,aims at directly and nondestructively evaluate the mechanical properties of wood composite panel,and proposes a new method using nodal line simply support vibration,which is approachable,reliable and suitable for both laboratory and on-line testing.An experimental setup is developed after deep exploration the detection theory.A series testing is done to validate the new detection theory.The main work content and conclusions are as follows:Explored the plate vibration characteristics under two nodal-line simply support boundary condition and the detection theory which was evaluation the elastic modulus and in-plane shear modulus of the quasi-isotropic panels or orthotropic panels based on their vibration characteristics.An equation to release the relationship between the elastic modulus,in-plane shear modulus and the vibration frequency,density,and size of the plate was established.Experimental modal analysis was first performed to determine the modal parameters(modal or resonance frequency,mode damping,mode shape)of 3 different thickness full-size middle density fiber board(MDF)and 4 thickness full-size oriented strand board(OSB)under two nodal-line simply support condition.The result show that:the vibration mode shape and mode sequence of different thickness full-size MDF panels were the same and the first mode shape was always mode(2,0).For the full-size OSB panels,the first mode shape and the third mode shape were mode(2,0)and mode(2,1),respectively.Although the mode(2,2)can't find within first the seven orders of few OSB panels,most OSB panels'seventh mode shape was mode(2,2).As an experimental setup was developed based on the new detection theory.Pre-test results show that the device has good repeatability.For 9 different point's excitations,including the center of the plate,the four corners,and the midpoints of the four sides,obtained frequencies is closed and the detection error can be ignored.The laser sensor on the setup can detect the high-order vibration frequency of the plate,and the measured first seven-order vibration frequency is correct.A free vibration test under two nodal line simply supported boundary condition were conducted on full size MDF panels,to nondestructive evaluation the modulus of elasticity and in-plane shear modulus of panels.The panels were then cut into small specimens for determination of mechanical properties and were conducted on static bending test.The results show that:There is a significant linear relationship between the modulus of elasticity obtained from vibration test and static bending test.The modulus of elasticity obtained from vibration test show a good linear relationship with the MOR,and both correlation coefficients were higher than 0.9.A free vibration test under two nodal line simply supported boundary condition were conducted on full size OSB panels to nondestructive evaluation the modulus of elasticity and in-plane shear modulus of panels.Half of the panels were then cut into small specimens and were conducted on static bending test.The results show that:the major strength direction modulus of elasticity of full-size OSB panels obtained from vibration test showed an excellent agreement with the modulus of elasticity from the static bending test and showed an excellent agreement with the modulus of rupture.Both correlation coefficients were higher than 0.84.Although the minor strength direction modulus of elasticity obtained from vibration test and the static bending test show linear relationship,the correlation coefficient wasn't as high as those from the major strength direction.The research results show that the new detection theory based on two nodal-line supported vibration can be used to rapid evaluate the elastic modulus and in-plane shear modulus of full-size quasi-isotropic or orthotropic wood composite panels and be used to predict the MOR.The experimental setup developed on this study can be a reference to further develop the on-line quality control system.The research results lay a foundation to replace the traditional destructive test by nondestructive test to rapidly evaluation the mechanical properties of full-size panels.