Size Effect in Paper Fiber-Reinforced Gypsum Panels Under In-Plane Bending
Keywords:
Paper fiber-reinforced gypsum panels, in-plane bending strength, size effect, strain softeningAbstract
This paper discusses the influence of the size effect on the in-plane bending strength of paper fiberreinforced gypsum panels. The incombustible composite material consists of randomly dispersed, recycled paper fibers embedded in a gypsum matrix. The brittleness of the material is considerably lower as compared to classical gypsum board. The panels are primarily employed in building industry for sheathing and bracing of timber and steel frame wall elements and for flooring applications.
The size effect study was performed on 3-point bending specimens that were identical in thickness, being 12.5 mm; depth however, with seven different dimensions was ranging from 10 to 320 mm. The experiments, for which the sample size was nominally eleven specimens per depth, were performed with a constant cross-head rate until complete separation of the specimens. The load-deflection curve was completely stable throughout the loading, even on the descending load branch beyond peak load. Thus, paper fiber-reinforced gypsum panels represent a strain-softening material. The nonlinearity of the stressdisplacement curves becomes more accentuated near peak load for smaller depths. This can be explained by the increasing ratio of the fracture process zone length to the specimen depth.
The tests revealed a nonlinear strength reduction with increasing specimen size, which was fitted by a one-parameter power law equation based on a Gauss-Newton approach. The statistical analysis of the fitted size effect curve verified the basic assumptions of normally distributed residuals and of a constant variance of the different samples. Furthermore, analysis of the variance revealed the adequacy of the chosen model function. For statistical inference on the population, confidence intervals are given for the model parameter and for the mean and individual strength values.
References
Aicher, S., and W. Klöck. 2000. Fracture modelling of wood fiber gypsum panel. Pages 469-480 in Proc. Int. Conf. on Wood and Wood Fiber Composites, Stuttgart, Germany.nAmerican Society For Testing and Materials (ASTM). 2003a. Standard test methods for physical testing of gypsum panel products. ASTM C473. ASTM. West Conshohocken, PA.nAmerican Society For Testing and Materials (ASTM). 2003b. ASTM C 1278 Standard specification for fiber-reinforced gypsum panels. ASTM, West Conshohocken, PA.nAmerican Society For Testing and Materials (ASTM). 2004. ASTM C 79 Standard Specification for treated core and non-treated core gypsum sheathing board, ASTM, West Conshohocken, PA.nBates, D. M., and D. G. Watts. 1988. Nonlinear regression analysis and its applications. John Wiley & Sons Inc., New York, NY.nBazant, Z. P., and J. Planas. 1998. Fracture and size effect in concrete and other quasibrittle materials. CRS Press, Boca Raton, FL.nEuropean Committee For Standardization (CEN). 2003. En 789 "timber Structures, Test methods—determination of mechanical properties of wood based panels". En 789, CEN, Brussels, Belgium.nGerman Institute For Building Technology (DIBt). 2002. CUAP Large-sized fiber gypsum panels used for walls of prefabricated houses (CUAP). DIBt, Berlin, Germany.nGerman Institute For Building Technology (DIBt). 2004. European Technical Approval "Fiber gypsum boards used for planking and lining of components". ETA-03/0050. DIBt, Berlin, Germany.nHummel, H.-U. 2000. Advanced gypsum fiberboard products for high end applications in the building industry. Pages 356-368 in Inorganic-bonded wood and fiber composite materials, Vol. 7, Sun Valley, ID.nICBO Evaluation Service (ICBO). 1999. Acceptance criteria for nonpaper-faced fiber-reinforced gypsum panels used as an alternate to gypsum board. (ICBO AC 158. ICB) Whittier, CA.nMiller, D. P., and M. R. Lynn. 1998. Development and scale up of USG's gypsum fiberboard technology. Pages 4-12 in Inorganic-bonded wood and fiber composite materials, Vol. 6, Sun Valley, ID.n
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