Publication: Aplicación de la tecnología de adhesivos en estructuras multimaterial: empleo de adhesivos tenaces
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2020-01
Defense date
2020-01-17
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Abstract
En esta Tesis Doctoral se ha estudiado la problemática actual existente en estructuras de acero utilizadas tanto en el ámbito del transporte de pasajeros como en aplicaciones de ingeniería civil. Este tipo de estructuras están sometidas durante su vida útil a un proceso de fatiga mecánica que desencadenará en fallos indeseados y problemas de seguridad.
Los métodos de fabricación actuales, basados principalmente en la soldadura, hacen que las estructuras sean muy rígidas, y por tanto que su comportamiento frente a la fatiga mecánica no sea el adecuado. Se propone una solución basada en el uso de adhesivos estructurales elásticos y materiales compuestos de matriz polimérica reforzados con fibra de carbono (CFRP). El problema ha sido resuelto en superestructuras de autobús mediante el diseño y fabricación de un nuevo nodo de CFRP unido mediante un adhesivo de poliuretano elástico a la estructura. Por otro lado, en estructuras de ingeniería civil se propone el uso de piezas de CFRP unidas a la estructura mediante un adhesivo epoxi elástico.
La resistencia de las nuevas uniones frente a los esfuerzos a los que estará sometida ha sido garantizada de forma experimental y por medio de análisis de elementos finitos, estudiando las singularidades mediante el “Intensity of Singular Stress Field” (ISSF). Los resultados obtenidos son excelentes, mostrando las nuevas uniones valores de resistencia ampliamente superiores a las solicitaciones requeridas. Del mismo modo, se ha dotado al conjunto de la elasticidad suficiente, mejorando el comportamiento a fatiga de las estructuras estudiadas.
In this Doctoral Thesis the current problems in steel structures used both in the fields of passenger transport and civil engineering applications are studied. These types of structures are subjected to mechanical fatigue during their useful life that will lead to unwanted failures and safety problems. Current manufacturing methods, based mainly on welding, make the structures very rigid, and therefore their behavior against mechanical fatigue is not adequate. A solution based on the use of ductile structural adhesives and carbon fiber reinforced polymers (CFRP) is proposed. The problem has been solved in bus superstructures by designing and manufacturing a new CFRP node joined by a ductile polyurethane adhesive to the structure. On the other hand, in civil engineering structures the use of CFRP pieces attached to the structure by means of a ductile epoxy adhesive is proposed. The resistance of the new joints against the stresses to which they will be subjected has been guaranteed experimentally and through finite element analysis, studying the singularities by means of the “Intensity of Singular Stress Field” (ISSF). The results obtained are excellent, and the new joints show resistance values far superior to the system requirements. Likewise, the structure has enough elasticity, and therefore fatigue behavior has been improved.
In this Doctoral Thesis the current problems in steel structures used both in the fields of passenger transport and civil engineering applications are studied. These types of structures are subjected to mechanical fatigue during their useful life that will lead to unwanted failures and safety problems. Current manufacturing methods, based mainly on welding, make the structures very rigid, and therefore their behavior against mechanical fatigue is not adequate. A solution based on the use of ductile structural adhesives and carbon fiber reinforced polymers (CFRP) is proposed. The problem has been solved in bus superstructures by designing and manufacturing a new CFRP node joined by a ductile polyurethane adhesive to the structure. On the other hand, in civil engineering structures the use of CFRP pieces attached to the structure by means of a ductile epoxy adhesive is proposed. The resistance of the new joints against the stresses to which they will be subjected has been guaranteed experimentally and through finite element analysis, studying the singularities by means of the “Intensity of Singular Stress Field” (ISSF). The results obtained are excellent, and the new joints show resistance values far superior to the system requirements. Likewise, the structure has enough elasticity, and therefore fatigue behavior has been improved.
Description
Mención Internacional en el título de doctor
Keywords
Estructuras de acero, Fatiga mecánica, Adhesivos estructurales elásticos, Materiales compuestos de matriz polimérica, Análisis de elementos finitos, Mechanical testing, Mechanical properties, Thermal properties, Adhesive structural joints, Polymer-matrix composites (PMCs), Carbon fiber reinforced polymers (CFRP), Steel-CFRP joints