BRIEF ORIGINAL Poisson’s ratio of the MDF in respect to vertical density profile Va ´clav Sebera • Jan Tippner • Milan S ˇ imek • Jan S ˇ rajer • David De ˇcky ´ • Hana Klı ´mova ´ Received: 18 April 2013 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract The work deals with Poisson’s ratios (PR’s) of medium density fiberboard (MDF) measured using digital image correlation and correlated to vertical density profiles (VDP). MDFs of four different thicknesses were first scanned by X-ray to obtain VDPs and then subjected to compression while measuring by DIC. PR’s of MDF reveal low correlations with VDP ( \ 0.08), but strong local behavior ranging from 0.025 to 0.06 for 12 mm thickness, from 0.018 to 0.105 for 18 mm, from 0.03 to 0.175 for 25 mm, and from 0 to 0.43 for 38 mm. 1 Introduction Medium density fiberboard (MDF) is an important ligno- cellulosic material with increasing production in the field of both furniture and housing industry. Despite the wide use of MDF, its properties are rarely explained in literature by a fully orthotropic material model (3 normal and 3 shear elastic moduli and 3 Poisson’s ratios). These data are not only important for further research work but also serve as necessary input data for numerical computations (FEM, FDM, MPM etc.) in engineering work that includes MDF material. Moreover, MDF can be examined as a pseudo- layered material since it exhibits a non-uniform vertical density profile (VDP) resulting from the manufacturing process (Wang et al. 2001). VDP is important because it determines MDF’s local material properties such as elastic moduli, Poisson’s ratios and others (Kelly 1977, Wang et al. 2001). The importance of the variability of Poisson’s ratio is marginalized in many different fields, for instance in material mechanics it is commonly assumed to be fixed and about 0.3 (Greaves et al. 2011). Similarly, one of the least examined properties of MDF is its Poisson’s ratio (PR’s), especially in respect to its VDP although determination of PR’s of wood-based composites (WBC’s) has been done some time ago. For instance Hunt and Suddarth (1974) used both experimental and analytical technique based on the FEM to measure and predict elastic properties of a strandboard. Their predicted value of PR in the main plane (m 12 ) was 0.15, while it was between 0.118 and 0.125 when measured using strain gauges. More closely to MDF, Moarcas and Irle (1999) measured PR’s of the particle- board main plane (m 12 ) on both compression and tension side when it was loaded by 4-point bending. They found that PR’s of particleboards coming from different produc- ers differ significantly (0.216 vs. 0.176), but agree with each other on both sides of the sample. Ganev et al. (2005) investigated PR’s on two planes of the MDF (parallel to manufacturing at main plane—m 12 , and perpendicular to manufacture direction—m 13 ). For both m 12 and m 13 no sta- tistically significant changes occurred when density chan- ged. In case of m 13 , two of three density and MC levels have experienced differences—m 13 decreased with higher den- sity and higher MC. Pavlekovics et al. (2008) determined V. Sebera (&) Á J. Tippner Á D. De ˇcky ´ Á H. Klı ´mova ´ Department of Wood Science, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zeme ˇde ˇlska ´ 3, 613 00 Brno, Czech Republic e-mail: seberav@gmail.com M. S ˇ imek Department of Furniture, Habitat and Design, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zeme ˇde ˇlska ´ 3, 613 00 Brno, Czech Republic J. S ˇ rajer Department of Wood Processing, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zeme ˇde ˇlska ´ 3, 613 00 Brno, Czech Republic 123 Eur. J. Wood Prod. DOI 10.1007/s00107-014-0780-1