Acta Polytechnica CTU Proceedings doi:10.14311/APP.2017.13.0157 Acta Polytechnica CTU Proceedings 13:157–161, 2017 © Czech Technical University in Prague, 2017 available online at http://ojs.cvut.cz/ojs/index.php/app METHODOLOGY FOR MEASURING THE SHEAR STRESS OF PLASTERBOARDS Ondřej Zobala, b, ∗, Robert Járaa, b, Martin Hataja, b a Czech Technical University in Prague, University Centre for Energy Efficient Buildings, Třinecká 1024, 273 43 Buštěhrad, Czech Republic b Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, 166 29 Prague 6, Czech Republic ∗ corresponding author: ondrej.zobal@fsv.cvut.cz Abstract. Plasterboards have to meet many requirements for certification. The mechanical properties of itself plasterboard are one of them. The important mechanical property of the plasterboard is the shear strength perpendicular to the plane of the board. The European Standard refers to performing the relevant test for the procedure set out in the wood standard EN 789. But is this methodology for plasterboard the most suitable? This paper compares this recommended method with the alternative method according to the American Standard ASTM D5379 with indicating the results of a specific measurement. Keywords: Plasterboard, shear strength perpendicular to the plane of the board, EN 789, ASTM D5379. 1. Introduction The plasterboard is pressed gypsum mass between two paper cartons for dry construction. This board can be used for reconstructions and new buildings for the construction of partitions, floors and ceilings. The plasterboard can protect against noise, moisture and fire [1]. Marking, definition of properties and test methods for gypsum boards are prescribed standard EN 520 + A1 from the 2010 which, moreover, unifies requirements and designations throughout Europe. Essential requirements include the declared tensile strength in bending and sag, shear strength, compres- sive strength, hardness and minimum required values of modulus of elasticity for individual stresses [1–5]. All required mechanical properties for certification are given in Tab. 1. Standard EN 520 + A1 defines 8 types of plasterboard: (1.) type A – gypsum plasterboard, (2.) type H – plasterboard with reduced water absorp- tion rate, (3.) type E – gypsum sheathing board, (4.) type F – gypsum plasterboard with improved core adhesion at high temperature, (5.) type P – plasterboard, (6.) type D – gypsum plasterboard with controlled density, (7.) type R – gypsum plasterboard with enhanced strength, (8.) type I – gypsum plasterboard with enhanced sur- face hardness. This paper addresses the determination of shear strength perpendicular to the plane of the board. Eu- ropean standards DIN 18180 from 2014 and EAD 07001-01-0504 from 2016 refer to the shear strength test perpendicular to the plane of the board to EN 789, which is, however, focused to wood-based boards [6– 8]. It has been found that the shear strength test perpendicular to the plane of the board according to EN 789 is performed very rare in test institutes in the Czech Republic (two places) and only one test facility has been discovered on the university campus. For these two reasons, we decided to try a different and more accessible way of testing. The US stan- dard ASTM D5379 for testing the shear properties of composite materials was finally chosen as an alter- native shear strength test perpendicular to the plane of the board [9]. The paper compares results and measurement procedures these two standards. 2. Methodology of measurement 2.1. Standard EN 789 The test specimen had the dimensions of 450×900×thickness of board [mm] and each board was cut one in the longitudinal direction and one in the transverse direction. We needed wooden or steel guide parts for fixing the test specimen. The guide parts had to meet the criteria (minimum dimensions, same humidity as the test specimen, minimum strength and rigidity). The connection of the guide parts and test specimen had to be done with a suitable adhesive. The static scheme is shown in Fig. 1 and Fig. 2 shows a load arrangement for a shear strength test perpendicular to the plane of the board. 157 http://dx.doi.org/10.14311/APP.2017.13.0157 http://ojs.cvut.cz/ojs/index.php/app O. Zobal, R. Jára, M. Hataj Acta Polytechnica CTU Proceedings Mechanical properties Designa-tion Dir. [°] Nr. of tests Spec. width [mm] Spec. length [mm] Bending strength perpendicular to the plane of the board – in the longitudinal direction fm,0,k 0 3 400 300 Bending strength perpendicular to the plane of the board – in the transverse direction fm,90,k 90 3 400 300 Modulus of elasticity in bending perpendicular to the plane of the board – longitudinally Em,0,mean 0 - - - Modulus of elasticity in bending perpendicular to the plane of the board – transversely Em,90,mean 90 - - - Shear strength in the plane of the board – longitu- dinally fv,0,k 0 3 500 600 Shear strength in the plane of the board – trans- versely fv,90,k 90 3 500 600 Modulus of elasticity in shear in the plane of the board – longitudinally Gv,0,mean 0 - - - Modulus of elasticity in shear in the plane of the board – transversely Gv,90,mean 90 - - - Compressive strength perpendicular to the plane of the board – longitudinally fc,0,k 0 3 400 400 Compressive strength perpendicular to the plane of the board – transversely fc,90,k 90 3 400 400 Bending strength in the plane of the board – in the longitudinal direction fm,0,k 0 3 400 300 Bending strength in the plane of the board – in the transverse direction fm,90,k 90 3 400 300 Modulus of elasticity in bending in the plane of the board – longitudinally Em,0,mean 0 - 6 6 Modulus of elasticity in bending in the plane of the board – transversely Em,90,mean 90 - - - Compressive strength in the plane of the board – longitudinally fc,0,k 0 3 400 400 Compressive strength in the plane of the board – transversely fc,90,k 90 3 400 400 Modulus of elasticity in compressive in the plane of the board – longitudinally Ec,0,mean 0 - - - Modulus of elasticity in compressive in the plane of the board – transversely Ec,90,mean 90 - - - Tensile strength in the plane of the board – longitu- dinally ft,0,k 0 3 50 350 Tensile strength in the plane of the board – trans- versely ft,90,k 90 3 50 350 Modulus of elasticity in tensile in the plane of the board – longitudinally Et,0,mean 0 - - - Modulus of elasticity in tensile in the plane of the board – transversely Et,90,mean 90 - - - Shear strength - core + carton fshear,max - 6 600 170 Determination of surface hardness of the board - - 6 300 400 Table 1. Comparison of test of the shear strength perpendicular to the plane of the board according to the standards EN 789 and ASTM D5379. 158 vol. 13/2017 Methodology for measuring the shear stress of plasterboards Figure 1. Static scheme of the test of shear strength perpendicular to the plane of the board [6]. Figure 2. The load arrangement for a shear strength test perpendicular to the plane of the board according standard EN 789 (dimensions are in mm) [8]. All test specimens were loaded with incremental strain at a constant rate of 2 mm/min until failure. The shear strength perpendicular to the plane of the board was given by the following Equation 1: fv = Fmax l.t , (1) where fv is shear strength perpendicular to the plane of the plate [MPa], Fmax is the maximum load at fail- ure [N], l is the length of the test specimen measured along the centerline of the shear area [mm], t is the average thickness of the test specimen measured at two points along centerline the shear area [mm]. 2.2. Standard ASTM D5379 The test specimen had the dimensions of 19.1 × 76.2× thickness of board [mm] and it was necessary to cut the specimens in the longitudinal and transverse di- rections from each board. No guide parts were needed to fasten the test specimen. Loading scheme was the same as for the standard EN 789 (Fig. 1). The load- ing arrangement with the shape and size of the test specimen for the shear strength test perpendicular to the plane of the board according to ASTM D5379 is shown in Fig. 3. The strength evaluation was per- formed according to Eq. 1. Figure 3. The load arrangement for a shear strength test perpendicular to the plane of the board with test specimen according standard ASTM D5379 (dimen- sions are in mm) [10]. 3. Results of measurement The number of test specimens according EN 789 was 6 pieces (3 different boards, 1× longitudinal and 1× transverse direction from each board). The num- ber of test specimens according ASTM D5379 was 30 pieces (3 different boards, 5× longitudinal and 5× transverse direction from each board). Fig. 4 shows a shear strength test perpendicular to the plane of the board according to ASTM D5379. The characteristic value of shear strength accord- ing to EN 789 was in the longitudinal and transverse direction same 2.8 MPa. The shear strength accord- ing to ASTM D5379 had characteristic value in the longitudinal direction of 3.1 MPa and in the trans- verse direction of 2.7 MPa. The differences of values of shear strength with the standard deviation results under 10% were minimal. 159 O. Zobal, R. Jára, M. Hataj Acta Polytechnica CTU Proceedings Standard Size of the testspecimen [mm] Difference of characteristic values [% ] Note EN 789 600×900×thickness fv,0,k = 10.7 problem with fastening test specimen ASTM D5379 19.1×76.2×thickness fv,90,k = 3.5 - Table 2. Comparison of test of the shear strength perpendicular to the plane of the board according to the standards EN 789 and ASTM D5379. Figure 4. Test of shear strength perpendicular to the plate plane according to ASTM D5379. Figure 5. Characteristic values of shear strength perpendicular to the plane of the plate according to the standards EN 789 and ASTM D5379. 4. Conclusions As is shown in Tab. 2, values of shear strength mea- surements according to EN 789 and ASTM D5379 are very similar. The EN 789 standard is determined pri- marily for wood-based materials. The test specimens according to EN 789 are very large and there is a problem with their attachment and ensuring stability during the test. A numerical model will be created to comparing the results according to EN 789 and ASTM D5379 on the basis of the obtained test parameters in the next phase of our work. Acknowledgements This work has been supported by the Faculty of Civil Engineering, Czech Technical University in Prague (SGS project No. SGS16/201/OHK1/3T/11) and by the Min- istry of Education, Youth and Sports within National Sustainability Programme I, project No. LO1605. References [1] Gypsum unique properties in buildings. http: //www.eurogypsum.org/about-gypsum/properties/. [2] Plasterboards according to european standards. http://imaterialy.dumabyt.cz/rubriky/ drevene-a-montovane-konstrukce/ sadrokartonove-desky-podle-evropskych-norem_ 101335.html. [3] CNI. Gypsum plasterboards – Definitions, requirements and test methods. First printing. Prague, 2010. [4] D. Supik. Analysis of selected mechanical properties of construction materials for wood building. thesis statement. Mendel University in Brno, 2009. [5] C. Petrone, G. Magliulo, G. Manfredi. Mechanical properties of plasterboards: experimental tests and statistical analysis. Journal of Materials in Civil Engineering 28(11):04016129, 2016. [6] DIN. Gypsum plasterboards – Definitions, requirements and test methods. First printing. Berlin, 2014. [7] EAD. Gypsum plasterboard for load-bearing applications. First printing. EOTA, 2016. [8] CNI. Timber structures – Test methods – Determination of mechanical properties of wood based panels. First printing. Prague, 2005. [9] D. ASTM. 5379:“standard test method for shear properties of composite materials by the v-notched beam method”. Annual Book of ASTM Standards 100:235–47, 2012. 160 http://www.eurogypsum.org/about-gypsum/properties/ http://www.eurogypsum.org/about-gypsum/properties/ http://imaterialy.dumabyt.cz/rubriky/drevene-a-montovane-konstrukce/sadrokartonove-desky-podle-evropskych-norem_101335.html http://imaterialy.dumabyt.cz/rubriky/drevene-a-montovane-konstrukce/sadrokartonove-desky-podle-evropskych-norem_101335.html http://imaterialy.dumabyt.cz/rubriky/drevene-a-montovane-konstrukce/sadrokartonove-desky-podle-evropskych-norem_101335.html http://imaterialy.dumabyt.cz/rubriky/drevene-a-montovane-konstrukce/sadrokartonove-desky-podle-evropskych-norem_101335.html vol. 13/2017 Methodology for measuring the shear stress of plasterboards [10] Shear test fixture astm d5379. http://www.grip.de/pdf/THS600_Datasheet.pdf. 161 http://www.grip.de/pdf/THS600_Datasheet.pdf Acta Polytechnica CTU Proceedings 13:157–160, 2017 1 Introduction 2 Methodology of measurement 2.1 Standard EN 789 2.2 Standard ASTM D5379 3 Results of measurement 4 Conclusions Acknowledgements References