Kārlis Rocēns

Experimental and Numerical Investigation of Plywood Panel with Curved Ribs

Abstract Numerical and experimental investigations of plywood unbalanced sheets and plywood panel with curved ribs are done. The moisture diffusion coefficient and deformability of special type of unbalanced sheet that might be used in manufacturing of curved ribs are studied. Results show that rational time of thermal treatment is 2.5-3 hoursand temperature are proposed to provide a shape stability of plywood elements. The behaviour of small scale experimental model of three hinged triangular roof structure that is made of plywood panels with curved ribs is experimentally studied.

Prediction of the shape changes of hybrid laminated composite material sheet

Prediction of the shape changes of hybrid laminated composite material sheet The preservation of the initial shape of anticlastic composite material sheets by using reinforced plastic strengthening has been investigated in the work. For the modelling of sheet deformations the calculation model, developed by the authors, has been used for the determination of the thickness of anticlastic sheet rational strengthening, which provides changes of the original bending radius within the limits of preferable intervals under variable moisture conditions [1], as well as the finite element method, carried out by software ANSYS v.11 (henceforth FEM). The changes of the sheet bending radii and longitudinal deformations in the geometrical middle plane of unstrengthened sheet are assumed to be the main characteristics of the shape. Stresses and longitudinal deformations have been calculated in the layers of the hybrid composite material element under variable moisture conditions using FEM. The comparative research of the results calculated with the FEM and the developed calculation model showed that the difference between the results in the inspected three cases, when the composite timber material are strengthened on the top, bottom and both sides, does not exceed 3.3% for none of the cases. An opportunity has been demonstrated how to provide the original shape of anticlastic timber composite material sheets by using glass fibre reinforced plastic strengthening under variable moisture conditions, thus not exceeding the difference of 5%. The developed calculation model is proposed for the use in the predicting of curvature if the elements with the anticlastic shape are obtained by using the displacements of moisture changes in the layers of the sheet.