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Non-destructive Testing and Reliability Analysis of Wood-plastic Planks

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Tutor: GuJiYou
School: Northeast Forestry University
Course: Wood Science and Technology
Keywords: Wood-plastic planks,modulus of elasticity,maximum bending force,modulusof reptur
CLC: TS67
Type: PhD thesis
Year:  2013
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Abstract:
Wood-plastic plank (WPP) as a profile in the wood-plastic composites (WPC) is widely used in the field of construction, decoration, transportation and garden. In order to save timber and oil resources, to understand the mechanical properties and security in use of WPP, and to expand the scope of application of economic, environmental and recyclable WPP, this paper has carried out nondestructive testing (NDT) of mechanical properties, reliability analysis and prediction of a variety of WPP, and analyzed reliabilities of the two types of wood-plastic structural system.In the NDT, whether the stiffener WPP that wood fiber (or wood flour) reinforced new and recycled high density polyethylene (HDPE), and the different thickness (or density) WPP of wood flour reinforced HDPE as the test materials, respectivily, using three NDT methods (longitudinal transmission, longitudinal vibration and flexural vibration) and three point bending test metod, respectivily, the dynamic and static modulus of elasticity (MOE) of above WPP were measured, and the regression analysis between dynamic and static MOE was carried out, respectively. The results show that has a strong correlation between the dynamic and static MOE of WPP of new and recycled HDPE reinforced by wood fiber, and the mean values of dynamic and static MOE are almost same, so, the recycled HDPE is suitable for the production of WPP. The thickness and stiffener can improve the dynamic and static MOE of WPP, and the Regression curve between dynamic and static MOE of them is proportional relationship, respectively. The density of specimen can also improve the dynamic and static MOE of WPP, but, the Regression curve between dynamic and static MOE of different density specimens is not proportional relationship.Three WPP of wood flour reinforced HDPE as the test materials, the maximum bending force and modulus of repture (MOR) of specimens were obtained by the three point bending test, the reliabilities of different WPP were analyzed by first order second moment (FOSM) method, improved FOSM method, Monte Carlo method and checking point stochastic finite element method, respectively. The results showed that above four methods of reliability analysis are suitable to evaluate the reliabilities of three WPP, respectively. The reliabilities of different density WPP based on the FOSM method are99.95%and98.46%, respectively. The reliabilities of different thickness WPP based on the FOSM method are99.916%and85.31%, respectively. The reliability of WPP based on the improved FOSM method is99.9767%. The reliability of WPP based on the Monte Carlo method is83.90%. The reliability of WPP based on the checking point stochastic finite element method is98.461%.In the reliability analysis of wood-plastic cantilever structure, two performance functions of any j point and A point has a correlation coefficient through correlation analysis between them, the performance function was got, which impacted reliability of wood-plastic cantilever structure, the reliability of wood-plastic cantilever structure based on the FOSM method is99.7882%. In reliability analysis of single span double wood-plastic frame structure, the number of plastic hinges were14,8main failure institutions were determined by the fault tree analysis method, and the performance functions of8main failure institutions were established, then, reliability indexes and failure probabilities of these performance functions were calculated by the improved FOSM, the representative institutions were determined by correlation analysis between performance functions, finally, the failure probability of single span double wood-plastic frame structure was calculated by probabilistic network evaluation techniques, the reliability of single span double wood-plastic frame structure is91.098%.Two WPP of wood flour reinforced high density polyethylene as the test materials, the dynamic MOE, maximum bending force and MOR of specimens were obtained by the above dynamic and static test methods. The prediction model of maximum bending force was getted by regression analysis of the dynamic MOE and maximum bending force of specimens in Group1, the maximum bending forces of orther same specimens was predicted, and the reliability of orther same specimens was calculated by the FOSM method. The results showed that the predicted maximum bending force is slightly larger than the measured maximum bending force, and the reliability based on predicted maximum bending forces is also slightly larger than that based on measured maximum bending forces. The prediction model of MOR was also obtained by regression analysis between dynamic MOE and static MOR of specimens in Group1, the MOR of other same specimens was predicted by the prediction model, and the reliability of orther same specimens was calculated by the improved FOSM method, the results show that the predicted and measured MOR are almost same, and the reliabilities based on the predicted and measured MOR are approximately equal.In summary, three NDT methods are suitable for the measurement of the dynamic MOE of WPP. Four methods of reliability analysis can be used to evaluate the performance of WPP in the practical application. Through the establishment of the prediction model between dynamic and static mechanical properties of WPP, the reliability of other same WPP can be predicted by three NDT methods. The reliability wood-plastic structural system can also be evaluated using the theory and methods.
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