Predicting the Flexure Response of Wood-Plastic Composites from Uni-Axial and Shear Data Using a Finite-Element Model
Publication: Journal of Materials in Civil Engineering
Volume 26, Issue 12
Abstract
Wood-plastic composites (WPCs), commonly used in residential decks and railings, exhibit mechanical behavior that is bimodal, anisotropic, and nonlinear viscoelastic. They exhibit different stress-strain responses to tension and compression, both of which are nonlinear. Their mechanical properties vary with respect to extrusion direction, their deformation under sustained load is time-dependent (they experience creep), and the severity of creep is stress-dependent. Because of these complexities, it is beneficial to create a mechanics-based predictive model that will calculate the material’s response in situations that are too difficult or expensive to test experimentally. Such a model would also be valuable in designing and optimizing new structural shapes. Analysis and prediction of WPC members begins with the time-dependent characterization of the material’s axial and shear behaviors. The data must then be combined with a tool that can simulate mode-dependence, anisotropy, and nonlinear axial stress distributions that vary over the length of a member and evolve with time. Time-dependent finite-element (FE) modeling is the most practical way to satisfy all of these requirements. This paper presents an FE material model that was developed to predict the deflection of flexural members subjected to both quasi-static ramp loading and long-term creep. Predictions were made for six different WPC products, encompassing a variety of polymers and cross-sections. These predictions were compared with experimental testing and the model shows some success, particularly in the quasi-static response. Creep predictions were more accurate for solid polyethene-based materials than polypropylene-based hollow box sections.
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Acknowledgments
This research was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service (grant number 2005-35103-15230).
References
Abaqus version 6.9 [Computer software]. Velizy-Villacoublay, France, Dassault Systemes.
Adcock, T., Hermanson, J. C., and Wolcott, M. P. (2001). “Relationship between extrusion parameters and wood-plastic composite properties, engineered wood composites for naval waterfront facilities.” Project End Rep., Washington State Univ., Pullman, WA.
ASTM. (2003). “Standard test methods for flexural properties of unreinforced and reinforced plastics.” D790, West Conshohocken, PA, 11.
ASTM. (2005a). “Standard test method for flexural properties of unreinforced and reinforced plastic lumber and related products.” D6109, West Conshohocken, PA.
ASTM. (2005b). “Standard test methods for compressive and flexural creep and creep-rupture of plastic lumber shapes.” D6112, West Conshohocken, PA, 7.
Benham, P. P., and McCammond, D. (1971). “Studies of creep and contraction ratio in thermoplastics.” Plast. Polym., 39(140), 130–136.
Clemons, C. (2002). “Wood-plastic composites in the United States: The interfacing of two industries.” For. Prod. J., 52(6), 10–18.
Dean, G. D., and Broughton, W. (2007). “A model for nonlinear creep in polypropylene.” Polym. Test., 26(8), 1068–1081.
Dura, M. (2005). “Behavior of hybrid wood-plastic composite—fiber reinforced polymer structural members for use in sustained loading applications.” M.S. thesis, Univ. of Maine, Orono, ME.
Dura, M., Lopez-Anido, R. A., Dagher, H., Gardner, D., O’Neill, S., and Stephens, K. (2005). “Experimental behavior of hybrid wood-plastic composite fiber-reinforced polymer structural members for use in sustained loading applications.” 8th Int. Conf. on Wood and Biofiber Plastic Composites, Forest Products Society, Madison, WI, 131–137.
Ewing, P. D., Turner, S., and Williams, J. G. (1973). “Combined tension-torsion creep of polyethylene with abrupt changes of stress.” J. Strain Anal. Eng. Des., 8(2), 83–89.
Findley, W. N., Lai, J. S., and Onaran, K. (1989). Creep and relaxation of nonlinear viscoelastic materials: With an introduction to linear viscoelasticity, Dover, Dover, NY.
Gardner, D. J., and Han, Y. (2010). “Towards structural wood-plastic composites: Technical innovations.” Proc., 6th Meeting of Nordic-Baltic Network in Wood Material Science and Engineering (WSE), Tallinn Univ. of Technology Press, Tallinn, Estonia, 7–21.
Haiar, K. J. (2000). “Performance and design of prototype wood-plastic composite sections.” M.S. thesis, Washington State Univ., Pullman, WA.
Hamel, S. E. (2011). “Modeling the time-dependent flexural response of wood-plastic composite materials.” Ph.D. dissertation, Univ. of Wisconsin–Madison, Madison, WI.
Hamel, S. E., Hermanson, J. C., and Cramer, S. M. (2013a). “Mechanical and time-dependent behavior of wood-plastic composites subjected to bending.” J. Thermoplast. Compos. Mater., in press.
Hamel, S. E., Hermanson, J. C., and Cramer, S. M. (2013b). “Mechanical and time-dependent behavior of wood-plastic composites subjected to tension and compression.” J. Thermoplast. Compos. Mater., 26(7), 968–987.
Jambeck, J., Weitz, K., Solo-Gabriele, H., Townsend, T., and Thorneloe, S. (2007). “CCA-treated wood disposed in landfills and life-cycle trade-offs with waste-to-energy and MSW landfill disposal.” Waste Manage., 27(8), S21–S28.
Jiang, L., Wolcott, M., Zhang, J., and Englund, K. (2007). “Flexural properties of surface reinforced wood/plastic deck board.” Polym. Eng. Sci., 47(3), 281–288.
Klyosov, A. A. K. (2007). Wood-plastic composites, Wiley-Interscience, Hoboken, NJ.
Kobbe, R. G. (2005). “Creep behavior of a wood-polypropylene composite.” M.S. thesis, Washington State Univ., Pullman, WA.
LabVIEW 8.2 [Computer software]. Austin, TX, National Instruments.
Lindstrom, M., and Bates, D. (1990). “Nonlinear mixed effects models for repeated measures data.” Biometrics, 46(3), 673–687.
Marklund, E., Varna, J., and Wallstrom, L. (2006). “Nonlinear viscoelasticity and viscoplasticity of flax/polypropylene composites.” J. Eng. Mater. Technol., 128(4), 527–536.
Matlab [Computer software]. Natick, MA, Mathworks.
Rangaraj, S. V., and Smith, L. V. (1999). “The nonlinearly viscoelastic response of a wood-thermoplastic composite.” Mech. Time-Depend. Mater., 3(2), 125–139.
Schildmeyer, A. J., Wolcott, M. P., and Bender, D. A. (2009). “Investigation of the temperature-dependent mechanical behavior of a polypropylene-pine composite.” J. Mater. Civ. Eng., 460–466.
Smith, P., and Wolcott, M. (2006). “Opportunities for wood/natural fibre-plastic composites in residential and industrial applications.” For. Prod. J., 56(3), 4–11.
Tschoegl, N. W., Knauss, W. G., and Emri, I. (2002). “Poisson’s ratio in linear viscoelasticity–A critical review.” Mech. Time-Depend. Mater., 6(1), 3–51.
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© 2014 American Society of Civil Engineers.
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Received: Sep 4, 2013
Accepted: Jan 3, 2014
Published online: Jan 6, 2014
Discussion open until: Nov 30, 2014
Published in print: Dec 1, 2014
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