Testing Glueline Continuity in Standard-Size Hardwood Blanks by Mechanical Methods
Keywords:
Mechanical tests, static bending perpendicular to the grain, tension perpendicular to the grain, torsion, plate twist, glueline continuity, standard-size blanks, hardwoods, red oak, black cherry, yellow-poplarAbstract
Glueline continuity is very critical in standard-size hardwood blanks because the blanks are cut up into small furniture parts, and a small gap in the glueline of a blank may extend across the whole part—or a gap may appear as a crack in the final product. Strength is not a critical factor. The objective of this study was to determine if a gap in a glueline can be detected by mechanical means. Furniture manufacturers want to be sure that any blank that they buy will have continuous gluelines. Every blank should be nondestructively tested, and all blanks with a defective glueline should be rejected from the shipment.
Black cherry, red oak, and yellow-poplar standard-size blanks 24 inches wide and 0.75 inches thick were manufactured. Some blanks were crosscut into strips two inches along the grain. The other blanks were cut 24 inches long. Foil defect strips were placed in the middle glueline of some panels to create a gap, thus achieving a range of effective gluelines of 60, 75, 90, and 100%. Static bending perpendicular to the grain, tension perpendicular to the grain, and torsion tests were developed for testing these specimens. Five parameters—modulus of rupture and modulus of elasticity in bending, tensile strength, torsional shear strength, and modulus of rigidity—were measured to determine their sensitivity for detecting defective gluelines.
Based on the results of this study, tensile strength perpendicular to the grain is the most satisfactory parameter for detecting defective gluelines. Its combination of high sensitivity and low variability would result in the smallest amount of destruction of good panels, while failing a larger number of defective panels. It was found that mechanical methods are not appropriate for determining glueline continuity since none of the parameters studied is sufficiently sensitive to detect defects of 10% or less.
References
American Society for Testing and Materials. 1981. Part 22, Wood; Adhesives. Philadelphia, PA.nAraman, P. A., C. J. Gatchell, and H. W. Reynolds. 1982. Meeting the solid wood needs of the furniture and cabinet industries: Standard-size hardwood blanks. USDA For. Ser., NE-FES. RP NE-494.nBarrett, J. D. 1974. Size effects on tension perpendicular to the grain. Wood and Fiber 6(2):126-143.nBodig, J., and B. Jayne. 1982. Mechanics of wood and wood composites. Van Nostrand Reinhold Co., New York.nBohannon, W. 1966. Effect of size on the bending strength of wood members. USDA For. Prod. Lab. Res. P. FPL-56.nDean, M. A., and J. H. Kaiserlik. 1984. Non-destructive screening of hardwood specialty blanks. For. Prod. J. 34(9):51-56.nDean, M. A., and A. J. Kass. 1983. Predicting the bending strength of ladder rail stock. For. Prod. J. 33(9):9-16.nDibuy, J. J. 1970. Shear resistance of partially glued laminated beams. For. Prod. J. 20(8):17-24.nEhlbech, J., and F. Colling. 1985. Panel shear strength and shear modulus of beech plywood. Holz Roh-Werkst. 43(4):143-147.nEl-Osta, M. L. M., O. A. Badran, and A. O. K. El-Wakeel. 1979. Prediction of MOR from MOE for some Egyptian hardwoods. Wood and Fiber 11(3):147-154.nGamov, V. V. 1975. Comparative investigations on wood in tension perpendicular to the grain. For. Prod. A. 1976. No. 4735.nHesterman, N. D. 1986. Development of a mechanical method for testing standard-size hardwood blanks. M.S. thesis, West Virginia University, Morgantown, WV. 127 pp.nJohnson, J. W. 1977. Selection of low-strength pieces by NDT: Douglas-fir and hem-fir 2 x 4's in flexure. For. Prod. J. 27(8):53-56.nKoch, C. B. 1983. Relationship of bending strength to stiffness of yellow-poplar 2 x 4's. For. Prod. J. 33(6):17-20.nKunesh, R. H., and J. W. Johnson. 1974. Effect of size on tensile strength of clear DF and HF dimension lumber. For. Prod. J. 24(8):32-36.nLiska, J. A. 1950. Effect of rapid loading on the compressive and flexure strength of wood. USDA For. Prod. Lab. R FPL-1767.nMadsen, B. 1975. Duration of load tests for wood in tension perpendicular to the grain. For. Prod. J. 25(8):48-53.nMcNatt, J. P. 1984. Static bending properties of structural wood-based panels; large panels vs. small-specimen tests. For. Prod. J. 34(4):50-54.nMcNatt, J. P. 1975. Effect of rate of loading and duration of load on properties of particleboard. USDA For. Prod. Lab. RP FPL-270.nMiller, D. G. 1964. Effect of tolerance on selection efficiency of non-destructive strength tests of wood. For. Prod. J. 14(4):179-183.nOsvenskii, B. A., and V. A. Akopyan. 1976. The resistance of wood to bending across the grain. For. Prod. A. 1977. No. 979.nRasmussen, E. F. 1961. Dry kiln operator's manual. USDA For. Ser. Ag. Hdbk. No. 188.nReynolds, H. W., and C. J. Gatchell. 1979. Marketing low-grade hardwoods for furniture stock—A new approach. USDA For. Ser., NE-FES RP NE-444.nReynolds, H. W., P. A. Araman, C. J. Gatchell, and B. G. Hansen. 1983. System 6 used to make kitchen cabinet C2F blanks from small-diameter, low-grade red oak. USDA For. Ser., NE-FES. RP NE-525.nSchniewind, A. P., and D. E. Lyon. 1973. Fracture mechanics approach to tensile strength perpendicular to the grain of dimension lumber. Wood Sci. Technol. (1):45-59.nSliker, A. 1975. Young's modulus as affected by strain rate, grain angle, and stress level. Wood Sci. 7(3):223-231.nStranger, A. G., and R. F. Blomquist. 1965. Block shear, cross-lap tension and glueline cleavage methods of testing glued joints. For. Prod. J. 15(12):468-474.nStrickler, M. D., and R. F. Pellerin. 1973. Rate of loading effect on tensile strength of wood parallel to the grain. For. Prod. J. 23(10):34-36.nTimoshenko, S. 1958. Strength of materials. D. Van Nostrand Co., Inc., Princeton, NJ.nTimoshenko, S., and S. Woinowsky-Krieger. 1959. Theory of plates and shells. McGraw-Hill Book Co., Inc., New York.nUSDA For. Prod. Lab. 1974. Wood handbook: Wood as an engineering material. For. Ser. Ag. Hdbk. No. 72.nWalters, C. S., and W. L. Reiss. 1977. Predicting MOR from MOE for small, clear specimens of oak and cottonwood. For. Prod. J. 27(6):51-53.nWangaard, F. F. 1950. The mechanical properties of wood. John Wiley and Sons, Inc., New York.n
Downloads
Published
Issue
Section
License
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.
