Study On Strength Of Furniture Construced Of Reconstitued Square Lumber Made Form Cotton Stalk

Reconstituted square lumber made from cotton stalk is a new type of wood substitute material, which has promising application in the future. By taking the reconstituted square lumber made from cotton stalk as the main study material, its 8 items physical and mechanical properties were tested by reference of related wood standards; Four kinds of traditional frame joints bonding modes were used to test and analysis the node joining strength, such as,run-through mortise and tenon joints, hidden mortise and tenon joints, double dowels joints,eccentric fittings joints. The effect of bolt category, diameter of guiding bore and screwing depth on reconstituted square lumber made from cotton stalk(end face, board side, board face) were investigated by orthogonal test. The study offers theoretical bases and data reference for reconstituted square lumber made from cotton stalk furniture.The main research achievement are as followings:(1) Reconstituted square lumber made from cotton stalk : adhesives was MDI, density was 0.75g/cm3, the moisture content was in 10% range. According to the experimental tests,elasticity modulus was 9.64 GPa, bending strength was 90.64 MPa, compression strength parallel to grain was 49.68 MPa, entire grain compressive strength was 8.13 MPa, part of cross grain compression strength was 21.53 MPa, shear strength was 15.32 MPa, top and botton surface hardness was 8.39 KN, front and back surface hardness was 8.39 KN, end surface hardness was 5.46 KN. By compared with 13 kinds wood, which were often used for furniture, the strength of reconstituted square lumber made from cotton stalk was suitable for furniture.(2) The value of reconstituted square lumber made from cotton stalk bending strength and pull-out strength of both components occurs by same way: run-through mortise and tenon joints strength > hidden mortise and tenon joints strength > the double dowels joints strength > the eccentric fittings joints strength. For bending strength, in L-form, the value of run-through mortise and tenon joints strength was respectively 60.9%、93.8%、176.4% higher than hidden mortise and tenon joints、the double dowels joints 、the eccentric fittings joints; in T-form, the data was 20.6%、67.1%、107.1%. For pull-out strength, the data was 35.5%、69.7%、146.6%.(3) The bending strength of reconstituted square lumber made from cotton stalk components was affected by structure. The joint bending strength of reconstituted square lumber made form cotton stalk T-form component was higher than that of the L-form component.The strength of T-form run-through mortise and tenon joints, hidden mortise and tenon joints, double dowels joints, eccentric fittings joints was respectively 10.7%、47.7%、28.4%、47.6% higher than L-form.(4) 4 kinds of node bending strength of reconstituted square lumber made from cotton stalk L-form and T-form component was lower than components of rubber wood and also the pull-out strength; but the bending strength and pull-out strength of double dowels joints and eccentric fittings joints of reconstituted square lumber made from cotton stalk was higher than particleboard and medium density fiberboard. So, reconstituted square lumber made from cotton stalk could be used in wood-based panel furniture. Using reconstituted square lumber made from cotton stalk to design furniture, should be preferred run-through mortise and tenon joints to eccentric fittings joints. Reconstituted square lumber made from cotton stalk furniture should be chose T-form.(5) The results showed that the nail and screw holding power of board face was well above the board side, nail and screw holding power of end face was only 57% of board face.Bolt category, diameter of guiding bore and screwing depth had no significant effect on nail and screw holding power of end face. Bolt category had significant effect on nail and screw holding power of board side. Nail and screw holding power of board face were significantly affected by bolt category and screwing depth. During the range of experiment, the optimal combination of screw structure of reconstituted square lumber made from cotton stalk(0.75g/cm3) was bolt category(slotted countersink head wood screws), diameter of guiding bore(3.2mm) and screwing depth(24mm). During the machining processing, the direction of screw-in should choose perpendicular to the cross grain rather than parallel to the rift grain. Bolt joint strength of furniture structure of main material could be increased in usage with using bolt with smaller pitch and wider tooth, decreasing of guiding bore as well as increasing of screwing depth.