1 Glulam process test
1. 1 Test materials The larch is 16~24cm in diameter. The origin is Linkou County, Heilongjiang Province. The diameter and volume of logs for non-structural laminated timber are shown in Table 1. The adhesive adopts imported polyvinyl acetate emulsion and polyurethane adhesive. The main quality indexes of various adhesives are shown in Table 2.
2 Adhesive main quality index glue
Viscosity type Appearance viscosity (Pa·s/25°C) pH value (25°C) Solid content (%) Storage period (month) Origin Polyvinyl acetate emulsion White milky 5～1575012 Japanese polyurethane glue Yellowish viscous 707596 Japan When adjusting the gum, the polyester emulsion was diluted with an appropriate amount of water to a viscosity of 15 Pa·s centipoise / 25 ° C. The curing agent of the polyurethane glue adopts isocyanate, and the preparation ratio is 100:15, and it must be uniformly stirred.
1.2 Process requirements for non-structural laminated materials
Material and drying Cut logs of 16~24cm in diameter into wooden sections of length 2m (the function is to reduce the bending of the logs and increase the yield of the materials), and then cut into plates on the sports car band saw machine. The thickness of the plates is 35mm, the plate yield is 55 8%. The plate is dried using a U-80 conventional drying chamber made in Canada, and the final moisture content of the plate is 85%. Sheet metal processing includes three processes: cross-section, double-sided planing and longitudinal sectioning. Before the sheet is processed, the sheet with a large transverse bend is cross-sectioned so that the full-length transverse bend of the sheet is less than 2 mm. In addition, due to the large warpage caused when the sheet is dried, the sheet having a large warp is longitudinally sectioned before double-sided shaving to reduce the warpage of the sheet, and the thickness of the sheet after double-sided shaving is 31 mm. Then, a multi-piece circular saw was used to longitudinally cut into a wooden strip having a width of 38 mm. Removing defects and removing defects is the main process of processing non-structural laminated materials. The standard for removing defects directly affects the yield. Referring to the Japanese unstructured glulam standard, the rules for removing defects in this test are shown in Table 3.
Table 3 Requirements level for sheet defects
Plate crack length (mm) insect eye (mm) resin edge (mm) clip skin (mm)
Nothing, no knots, cracks, decay, discoloration
Second-class live festival <10mm without dead knot, decay 30 or less 10 or less 30 or less 10 or less
Third-class live festival <30mm no dead knot 100 or less 30 or less 50 or less 30 or less
The proportion of defects removed is: 24 3% (the proportion of the plate), in which the proportion of various defects is: 43% of the knot, 17 2% of the crack, the skin, the resin edge, the insect eye 5 8%, the thickness is less than 13% , blunt edge 10 7%, decay 6 3%, other 3%. Finger joint processing finger joint processing conditions:
(1) Cutting conditions: There are preparatory cutting, using a chip milling cutter. The loading method is that the cutting edges are offset from each other, the number of rotations of the cutter shaft is 5000r/min, and the feeding speed is 3m/min. Tooth shape parameters: tooth length 11 4mm, tooth tip width 0 6mm, slope 6 6 °.
(2) Fitting condition: fitting degree 0 1 mm.
(3) Gluing conditions: the adhesive is made of polyvinyl acetate emulsion, the amount of glue is 0 16g/cm2 (single-sided glue), the pressing pressure is 6MPa, the pressing time is 5s, the bonding temperature is 18°C, and the curing time is 24h. The integrated processing integrated processing includes three steps of planing, gluing and assembling of finger joints. The four-sided planer is used for finger jointing, and the thickness and width of the planing allowance are both 25 mm. Gluing conditions: the adhesive is made of polyurethane glue, the amount of glue is 300g/m2 (double-sided glue), the bonding temperature is 18°C, the aging time is 10~20min, the bonding pressure is 0 8MPa, the pressing time is 40min, and the curing time is 24h. Glued wood sand gluing wood sanding is carried out on the SDM-52P sanding machine with two sides of sanding, and the sanding residual is 25 mm.
2 Strength test of laminated timber
2. 1 bending strength test specimen of finger joint
Tested according to the national standard GB1936-80, the bending strength and elastic modulus were tested. The test results are shown in Table 4.
3 The gluing performance test of the glulam consists of shear strength and peeling rate. The test is carried out according to the Japanese non-structural glulam standard. The test results are shown in Table 5. According to the Japanese Glulam Standard (Nonglin Provincial Notice No. 2035), the shear strength of the softwood is required to be greater than 7 MPa, the wood breaking rate is greater than 50%, the peeling rate of the sample is below 10%, and the peeling length of the same adhesive layer Less than 1/3 of the length of the adhesive layer is acceptable. The test results show that the shear strength, wood breaking rate and peeling rate all have satisfactory results. Using short-cycle industrial larch to make samples of furniture and interior decoration materials, the results show that the appearance of the product is beautiful, durable, and less deformation and cracking, improve the grade of furniture, and make furniture and interior decoration for the use of short-cycle industrial materials. Materials have opened up broad prospects.
4 Analysis of existing problems
3. 1 The final yield of glulam is 24 5%, which is equivalent to the production of 1m3 laminated timber from 4m3 logs. Therefore, the overall yield is still low, and the processed wood has more residues. In order to improve the utilization rate of wood, multi-level deep processing should be carried out in order to reduce the processing cost of the laminated timber.
3. 2 Larch is prone to deformation and cracking when it is dry, especially the warpage of the plate has a great influence on the yield of the laminated timber. Therefore, there is still a need for further research on the drying process.
3. 3 Larch has more resin, which makes it difficult to glue and surface the laminated timber. Therefore, we should actively look for the degreasing method of larch to ensure the effective use of larch.
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