SUMMARY
The ceramic tile industry and the Spanish one in particular, faces up to a highly saturated market and so needs to offer innovative products constantly, able to integrate functions which could be perceived by the user as added value. The new ceramic products have to be competitive in quality and look for an optimum from the economic and environmental point of view. Moreover they should facilitate transport and placing, and accomplish with the national and international regulations.
Ceramic tiles lightened by the execution of a back relief could be manufactured with substantially less raw material than the traditional one, which has an effect not only in the saving of weight, but also in the saving of production and transport energy, which improves the economic balance of the enterprise (especially now that the cost of natural gas and sand is achieving historic maximums) , providing the product with an environmental character that is starting to be demanded by the authorities and it is even more considered by consumers. Additionally, a lighter final product is attractive to builders, since it improves the working conditions at the building site. Nevertheless, lightened tiles are structurally different from the conventional one, and so is their mechanical and thermic behaviour. Because it is a constructive element it is necessary to know its response under working conditions and assure that it accomplishes with the valid standards.
This doctoral thesis aims at the objective of evaluating the convenience of lightened ceramic floorings employing the techniques of solid three-dimensional modelling and finite elements analysis, establishing at the same time the bases for an optimal definition of the back relief, understanding as an optimum the design that could combine in the aptest way weight saving and mechanic and thermic response, within the viability of the current serial manufacturing methods. Due to the very few antecedents found in the bibliography in this sense, this doctoral thesis opens a window to later studies and provides very valuable information to the design and production departments of the ceramic companies.
In order to achieve this objective, 9 different models were defined (2 reference models and 7 ones based on regular polygons) from which a total of 70 versions were generated (obtained by the variation of the back relief depth and the wall angle) which underwent 4 tests (mechanic and thermic) included in the regulations that applied to this kind of ceramics. After deciding that both mass and principal stresses (Rankine criterion), were the magnitudes to consider in the study, the maximal stresses of each version for each test were calculated, as much as their distribution. Next, 4 comparison coefficients supported in essential statistic tools were defined and according to them a suitability order was established.
Finally, thanks to the close collaboration with the firm KEROS CERÁMICA S.A. in the frame of the projects “Study of the manufacturing viability of low density tiles. ECOLIGHT Project” and “Integration of the glazing and decorating processes for the manufacturing of the ceramic tile Ecolight. DECOLIGHT Project”, it been verified that the employed methodology was appropriate comparing with the results obtained by means of the manufacturing in shoopfloor conditions and laboratory tests of several of the designs proposed in the thesis.
Altogether, it has been concluded that lightened models have different response against typical requests, so that, back reliefs could improve both raw material consumption and structural answer simultaneously. On the other hand, a parameter named “normalized thickness en” has been proposed, which could permit the calculation of the flexural strength R as fixed by the standard EN ISO 10545 “Baldosas Cerámicas”, which nowadays is not strictly viable for variable thickness ceramic floorings. In addition, a set of fundamental behaviour guidelines have been extracted and could be taken as a basis for the back relief design of any particular enterprise. Within the most general ones stands out the fact that the variation of the relief depth affects suitability more intensively than the variation of the wall angle, being found the best compound response (mass, mechanic and thermic) for intermediate values of both parameters.
With independence of these guidelines, this thesis proposes a principal of methodology for the geometric evaluation of floorings that could be extended to other kinds of ceramic products and to other design variables, for instance the dimensions of the format (length and width).