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journal of materials research and technology 2021;14:1630 e 1643
For the manufacture of the panels for this study (Fig. 1(a- c)), with an intermediate resin content of 13%, strands with dimensions on the order of 90 25 1 mm were used at a moisture content of 8% previously achieved by drying for 48 h at a temperature of 65 C. The Pu-castor oil resin was applied by spraying and the biomass, arranged in a metallic mold, was pressed at 5 MPa for 10 min at 100 C. After 72 h in the ambient curing process, the panels were sanded, and finally, the specimens were cut following the Longitudinal (alignment axis for the length of the outer layer strands) and Transverse (transverse axis for the length of the outer layers strands) di- rections (Fig. 1(d)). The specimens cut with the long dimension aligned in the longitudinal direction were designated SL and, the specimens with the long dimension aligned in the trans- verse direction were named ST (Fig. 1(e)).
objective of this study was to estimate the equivalent moduli of elasticity to each OSB panel layer, with a results-based method of the specimens bending test in the longitudinal and transverse directions of the panel. Computational modeling by the Ansys software [41] with a multi-layer model was used to validate the results of this research, and physical non-linearity was considered for better adjustment of the models.
2.
Materials and methods
2.1.
Manufacture of OSB panels for the study
To achieve the goal of this research, a total of eight OSB panels 400 400 mm in width were manufactured with strands of balsa wood ( Ochroma pyramidale ) waste glued with castor oil polyurethane resin (Pu-castor oil resin), that was applied at a content of 13% of the mass of wood particles. The thickness of 10 mm of the panels was composed at a layer proportion of 30:40:30 (outer - core - outer) resulting in a panel average density of 0.65 g/cm 3 , and the corresponding coefficient of variation of 8.1%. The OSB panels were manufactured in Research Nucleus on Materials for Biosystems & Laboratory of Construction and Ambience (Faculty of Animal Science and Food Engineering, University of S ~ ao Paulo, Brazil). Previously, Barbirato et al. [4] studied the feasibility of manufacturing OSB panels composed of balsa wood residues and Pu-castor oil resin, varying the density of the panels from 0.30 to 0.40 g/cm 3 and the resin contents varying from 11 to 15%. The best physical and mechanical properties were proven for the composition with the highest density and resin content [4].
2.2.
Mechanical properties resulting from specimens
tests
The parameterization of the models to represent the OSB panels behavior in the longitudinal and transverse directions was based on the results of specimens in static bending test at three points (Fig. 2 (a)) on a universal testing machine (Emic, Brazil). The load was applied at a constant crosshead speed of 6 mm/min on 10 specimens for each direction, according to the procedures described by European Standard EN 310 [42]. Taking into account the elastic region on the load versus deflection diagram comprised in the range of 10 e 40% of ulti- mate load according to ASTM D1037 [21], for the SL specimens the mean flexural rigidity value was 36,015,275.5 N mm 2 ,with a respective coefficient of variation of 16.3%. For the ST group of specimens, a lower mean value for the flexural rigidity of
Fig. 1 e Manufacture process of OSB panel of residual balsa wood: (a) particle separator; (b) mattress of strands; (c) thermo- hydraulic press; (d) finished panel and orientation direction of the strands; (e) Longitudinal and Transverse specimens.
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