| Fast-growing plantation of poplars is considered one of solution way to replace natural forests,meet the needs of human life,and solve the contradiction between timber supply and demand due to their fast growth and short rotation period.However,its wood has low density,low strength,easy deformation,weak texture,and is difficult to be widely used with high value.Aiming at the above-mentioned drawbacks and bottlenecks of the most important fast-growing artificial poplar wood in Shandong,this study attempts to adopt compression densification technology(ie compression technology)and high temperature heat treatment technology(ie thermal modification technology)to solve the key problems of low mechanical strength and poor dimensional stability of poplar wood;the technical solution combining pattern design and digital printing is used to solve the bottleneck problem of the weak texture of the poplar wood surface;then the two technical solutions are organically combined to make poplar into structure-decoration integrated material,aiming to face the main battlefield of the national economy and explore the application of poplar wood in important livelihood fields such as building structure and surface decoration,so as to realize the green solution of high efficiency and high value utilization.First,we explored the optimization technology of poplar veneer compression and thermal modification treatment technology.Then,the poplar veneer composite was constructed through orthogonal gluing,and the mechanical strength of the composite was evaluated according to the structure wood standards;on this basis,for the surface patterning design of composite materials,the pattern styles were screened through questionnaire surveys,and with the help of drawing software and digital printing technology,the decorative patterning of the poplar wood surface was realized,so that the poplar wood veneer was integrated into a structure-decoration composite material.The research results are as follows:(1)The mechanical properties of poplar veneer(3 mm thick)after compression treatment are remarkably improved compared with untreated wood,and its properties and density increase with the compression rate.The optimized compression process is as follows:the initial moisture content of 30%,the hot pressing temperature of 120?,the hot pressing pressure of 12.5 MPa,the hot pressing time of 1 h,and the compression rate of 60%.Under this process,the air-dry density of the compressed veneer can reach 0.88g/cm~3,which is125.6%higher than that of the untreated veneer;the hardness is between 5 H-6 H,which is 5?6 times higher than that of untreated veneer;The wear rate reaches 53.4 mg/100r,which is82%lower than that of untreated veneer;the modulus of elastic(MOE)reaches 25.6 GPa,which is 346%higher than that of untreated veneer;the modulus of rupture(MOR)reaches181 MPa,which is 184%higher than that of untreated veneer;both the elastic modulus and static bending strength exceed the specified index value of the strength grade of TC_T40according to the GB50005-2017"Wood Structure Design Standard"(elastic modulus 12,500MPa,static bending strength 27.9 MPa);however,the hygroscopic and springback expansion rate of the compressed veneer is as high as 4.97%(under 95%humidity),which is 55%higher than that of the untreated material,which is prone to deformation defects.(2)The optimized process of the further thermal modification treatment of the compressed veneer:nitrogen atmosphere for protection,thermal modification temperature is200?,and the thermal modification time is 1 h.Under this process,the air-dry density of the compressed-heat modified veneer reaches 0.85g/cm~3,the modulus of elastic(MOE)reaches20.8 GPa,the modulus of elastic(MOE)reaches 147 MPa,which still exceed the elastic modulus and static bending strength index value of TC_T40 according to the GB50005-2017"Wood Structure Design Standard".After heat treatment,the hygroscopic and springback expansion rate of the compressed veneer reached 2.28%(under 95%humidity),which is 118%lower than that of compressed veneer(4.97%).(3)The modified veneer was glued to 1.2cm laminated veneer lumber,wherein the laminated veneer lumber has a modulus of elastic of 27.7GPa and a modulus of rupture of193MPa;as for compressed-thermal modified veneer laminated composite,the modulus of elastic is 14.8 GPa,the modulus of rupture is 126.8Mpa,the compression strength parallel to grain is 64.8 MPa,the compression strength perpendicular to grain is 31.6 MPa,reaching the indexes of modulus of elasticity(12500 MPa),modulus of rupture(35 MPa),compression strength parallel to grain(23.2 MPa)and maximum strength index of compression strength perpendicular to grain(3.0 MPa)of the grade of TC_T40 according to the GB50005-2017"Wood Structure Design Standard";the hardness of cross section is 7.75KN/mm~2,which is144%higher than that of untreated plywood with the same thickness.(4)Focusing on the surface patterning design of structural materials,for indoor background wall applications,we conducted questionnaires and conducted a questionnaire survey on 182 random survey subjects,the survey feedback results are obtained as follows:the most popular pattern elements are landscape,accounting for 30.77%;geometry,accounting for 24.17%and plants,accounting for 23.08%.The most popular forms of expression are texture patterns,accounting for 40.11%;freehand patterns,accounting for26.37%and concrete patterns,17.58%.The most popular arrangements are free arrangement and divergent arrangement,both accounting for 28.56%,and symmetrical arrangement accounting for 27.49%.The most popular pattern color system is light color,accounting for59.34%.In addition,more than 69%of people pay much attention on the overall style when choosing patterns.This result serves as the theoretical basis for subsequent pattern design,and the target pattern is designed by using Photoshop and Adobe Illustrator,and then the pattern is printed on the modified poplar structural material surface through digital printing technology,so as to prepare structure-decoration integrated material.Finally,the satisfaction degree of the pattern on the surface of the integrated material was verified.The results of the questionnaire verification showed that the pattern was generally welcomed by the surveyed population.This study shows that the compression-heat modification technology can give poplar wood the key mechanical strength that meets the requirements of structural wood properties.By using digital printing technology,decorative patterns of various styles can be directly constructed on the surface of modified poplar structure material to meet the customized needs of different groups of people.This provides an innovative solution for exploring the efficient and high-value utilization of poplar wood. |
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