Research On The Plasma-modified Fiber Reinforced Laminated Veneer Lumber

The synthetically utilization of wood resources has always been a wood science and technology research focus,and has attracted wide attention.In response to the problems of artificially fast-growing wood,such as quagginess,low mechanical strength and large variability,and in order to improve the high-value utilization of fast-growing wood and expand its wide application in the field of structural bearing member.This study takes fast-growing poplar as the research object,and selects two types of fiber materials,glass fiber?GF?and carbon fiber?CF?as the reinforcement unit.Surface treatment of two types of fiber by DBD plasma and APPJ plasma,that aim to improve the bonding characteristics of the fiber surface for the fabrication of high-performance fiber-reinforced poplar laminate veneer lumber?LVL?,and explores its application in the field of load-bearing shaped laminate timber components.This paper mainly studied the plasma modification process of fiber reinforced materials and its composite process with poplar veneer,and the high-frequency fast gluing process of fiber reinforced laminates veneer lumber.To clarify the gluing mechanism of plasma modified fiber and poplar veneer to obtain fiber reinforced LVL products with reasonable technology and excellent performance,and explore the feasibility of applying it to the manufacture of load-bearing shaped laminated wood components.This research chose poplar veneer as base material,and the used adhesive is thermosetting phenolic resin.Plasma technology was used to modify the surface of GF and CF respectively,in order to obtain excelent interface bonding performance between fiber and poplar veneer.Based on that to obtain fiber-reinforced poplar LVL with good mechanical properties,and explore its application in the field of load-bearing shaped laminated wood components.The main conclusions are as follows:?1?DBD plasma and APPJ plasma were used to modify GF and CF,respectively,and glued them to poplar veneer.The results showed that the fiber surface roughness increased after plasma surface treatment,and the fiber surface introduced abundant oxygen-containing functional groups?C=O,C-O,and C-O-C?through the oxidation reaction,which significantly improves the fiber surface polarity and the total surface energy.Meanwhile,the water contact angle on the fiber surface was significantly reduced and the fiber surface wettability was increased after plasma modification.GFs were treated with the DBD plasma process power of 4.5 kW,the O content on the fiber surface increased significantly by 10.19%,the O/C ratio increased by 0.21,the total surface energy increased from 51.73 J·m^-2 to 61.38 J·m^-2,and the contact angle of water on the GF surface was reduced from 54.03°to 34.58°,and the bonding strength increased from 0.23MPa to 1.13 MPa.CFs were treated with the APPJ plasma process power of 6 kW,the O content on the fiber surface increased significantly by 6.22%,O/C ratio increased by 0.13,the total surface energy increased from 43.6 J·m^-2 to 63.14 J·m^-2,the contact angle of water on the CF surface declined from 66.4°to 34.6°,and the bonding strength increased from 0.56 MPa to 0.84MPa.?2?Plasma modified fiber reinforced poplar LVL was manufactured by the contact hot-pressing.The effects of sizing amount,group method and hot-pressing condition on the mechanical properties of fiber reinforced poplar LVL were studied.The results showed that:using the optimal sizing amount of 140 g/m²,the second outer layer blank,the hot pressing time of 30min and the hot pressing temperature of 130?,the maximum horizontal shear strength of GF reinforced poplar LVL was 12.67 MPa,MOR_max and MOE_max were 114 MPa and 16102 MPa,respectively.Using the optimum sizing amount of 120 g/m²,the second outer layer preform,25min hot pressing time and 130?hot pressing temperature,the CF reinforced poplar LVL has a maximum horizontal shear strength of 12.67 MPa,MOR_max and MOE_max were 102.1 MPa and15519 MPa,respectively.?3?Plasma modified GF reinforced poplar LVL was manufactured by the high-frequency hot-pressing.The result of mechanical properties of GF reinforced LVL showed that MOR and MOE will not increase with the sizing amount.MOR_max and MOE_max of the GF reinforced poplar LVL with the sizing amount 120 g/m² were 163.99 MPa and 23010 MPa,respectively.Compared with the contact hot-pressing,the high-frequency hot-pressing greatly shortens the hot-pressing time,which is only 1/10 of the contact hot-pressing time.?4?Plasma modified fiber reinforced fast-growing LVL with excelent mechanical strength was applied to reinforce curved parts of shaped laminated timber wood member,and the structural optimization design of the curved parts was achieved by finite element method.The results showed that the maximum stress of plasma modified GF reinforced"U"chair legs reached 58.1MPa,which was much higher than the mechanical requirements of poplar veneer laminates,which can meet the requirements of the size of"U"-chair frame.The curved parts of the"U"chair legs play a significant enhancement effect,in addition,the wood material saving rate reached16.7%.