Study On Dimensional Stability Analysis And Structural Optimization Of Wood-based Composite Door Based On Finite Element Method

Wood composite doors were the most popular form of wood door,with a substantial market share in both the commercial and residential house sectors.The biggest quality issue in the manufacturing and usage of wood composite doors was deformation,which limited the development of high-quality wood-based composite doors.As a result,it was critical to investigate the physical and mechanical properties of the wood composite door substrate,the interaction mechanism between door structure and wet deformation,and establish key technologies for dimensional stability control of wood composite doors,both theoretically and technically.In this paper,we used the finite element method to build an experimental platform for the numerical simulation of moisture absorption and deformation of door slats,to investigate the interaction mechanism between the physical and mechanical properties of medium density fiberboard(MDF),laminated veneer lumber(LVL),and hollow particle board and the dimensional stability of the door slats,to optimize the door slats using the response surface method,and to build an optimization model for the dimensional stability.The main research results are as follows:(1)Based on the theory of moisture absorption and expansion,a theoretical model of wet deformation of wood composite doors was built,and the physical and mechanical properties of wood composite door substrates were analyzed by quantitatively characterizing the required physical parameters of wood composite door substrates in the theoretical model.The analysis of the moisture content uniformity of the substrate revealed that the moisture content of MDF at the center was 7.82%lower than that at the edges;the moisture content of 40 mm LVL was 81%higher than that of 25 mm LVL;the thicker the LVL,the greater the difference in water content of the LVL core surface layer.The analysis of the difference in the wet expansion coefficient of the substrate revealed that the wet expansion coefficient of MDF in the thickness direction was 26.0 times that in the length direction and 19.5 times that in the width direction;the wet expansion coefficient of LVL in the thickness and horizontal grain direction was 26.0 times that in the longitudinal grain direction.The analysis of the effect of finishing materials on the deformation of door substrates led to the following conclusion:the moisture absorption deformation of single-finish MDF was greater than that of double-finish and unfinished.Analysis of the modulus of elasticity of the substrates showed that the difference in modulus of elasticity of MDF at different sampling locations was not significant,and the modulus of elasticity of LVL was 15.5 times higher for vertical loading than for parallel loading.(2)To improve the door structure of wood composite doors,a numerical simulation platform of wet deformation finite element simulation of wood composite doors was constructed based on the wet deformation theoretical model.The deformation of the door frame was located mostly in the area of the unfixed side stile and the corner of the stile’s junction.The combination of cross stile and side stile wrapping upper and lower stiles may more effectively control frame deformation;when the surface panel was added,the deformation of the frame became smaller,so the surface panel and frame can inhibit each other’s deformation.The width of the core board has an effect on the door deformation,and a core board strip with a width of 25 mm was the best choice for the door assembly.The analysis of door component configuration showed that when the number of door hinges was two and the position was Tp=1/4,the stress groove was set at the corner of the top and bottom stiles and the unfixed side stile area,which could inhibit the deformation of the door.The final optimized solution for the door structure reduced the deformation by 18.92%compared to the existing one.(3)The response surface method were used to optimize the structural dimensions of the door leaf and to build an optimization model for the door leaf assembly.The experimental results showed that as the thickness of the surface plate or the thickness of the frame increases,the comprehensive deformation of the door frame showed a trend of decreasing first and then increasing,and the influence on the comprehensive deformation of the door was in the following order:single side width>frame thickness>surface plate thickness,and the optimized optimal grouping scheme was:surface plate thickness was 3 mm,frame thickness was 28 mm,single side width was 75 mm.The model could quantitatively analyze the maximum moisture absorption deformation of the door under complex load by the surface plate thickness,frame thickness and frame single side width,through which the optimal door assembly process could be optimized.