Vol. 17, no. 1, pp. 223-232, enero-junio 2018 Revista UIS Ingenierías RESUMENEn esta investigación se realiza la modelación tridimensional del miembro residual de un amputado transfemoral que incluye la piel, el tejido graso, el músculo y el fémur residual. Se establecen las condiciones de carga para la fase de apoyo durante el ciclo de la marcha normal, la bipedestación y la marcha por escaleras de un amputado transfemoral de 88 kg y una estatura de 1.7 m. Se realizó un análisis de la incidencia de las condiciones de carga sobre los esfuerzos y deformaciones en el tejido muscular, para establecer su influencia sobre la generación de úlceras por presión internas en el miembro residual del amputado. Del análisis se obtuvo que el esfuerzo a compresión promedio más alto es cercano a 18.6 kPa y la deformación promedio más alta a compresión es de 56.8 %, esto sucede cuando se realiza marcha por escaleras o superficies inclinadas. La mayor concentración de esfuerzo y deformación se presenta en la zona distal del fémur residual en el tejido muscular. PALABRAS CLAVE:Úlceras por presión; úlceras por presión internas; UP; UPI; amputado transfemoral; elementos finitos; EF; biomecánica. ABSTRACTIn this research, three-dimensional modeling of the residual limb of a transfemoral amputee is performed, which includes skin, fat tissue, muscle and residual femur. The loading conditions are established for the support phase during the normal gait cycle, the standing and walking through stairs of a transfemoral amputee of 88 kg and a height of 1.7 m. An analysis of the incidence of load conditions on the stresses and deformations in muscle tissue was made to establish its influence on the development of deep tissue injuries (DTI) in the residual limb of the amputee. From the analysis it was obtained that the average compressive stress is close to 18.6 kPa and the highest average strain at compression is 56.8%, it happens when the individual is walking through stairs or slope. The maximum concentration of stress and strain occurs in the distal area of the residual femur in muscle tissue.

Over millennia nature has produced composite materials with excellent mechanical properties compared to the low properties of their base materials and has managed to obtain a good compatibility between stiffness and toughness; as a result, they are a good source of inspiration for material optimization for applications, such as increasing toughness and damage resistance, something that is difficult in conventional engineering materials. Nowadays eight structural elements are identified in biological materials: fibrous, helicoidal, gradients, layered, tubular, cellular, suture, and overlapping. Helical structures consist of stacks of ordered fibers that form layers that are rotated at a constant angle of inclination. These include plywood and Bouligand structures. Bouligand structures consist of an arrangement of fibrous laminates that completes a 180° turn and provides some biological materials with increased strength and toughness in multiple directions and exceptionally high fracture toughness. The classical composite materials mechanics provides some constitutive model approximations for this type of materials, but they still need to be studied and tested to properly understand their behavior. Injection molding, compression molding, hand layup, resin transfer molding, filament winding, pultrusion, and automated fiber placement are just a few of the traditional methods used to make fiber-reinforced polymer composites (FRPC). However, these traditional manufacturing techniques have a restriction on specific fiber alignment and demand expensive molds, dies, or lithographic masks. Additive manufacturing has the potential to replace many conventional manufacturing processes due to its ability to create complex geometries with customizable material properties and employ several materials simultaneously, among other things. Fused deposition modeling (FDM) is the most widely used manufacturing additive technique for manufacturing FRPC due to its low cost, low energy input, material consumption, and operation simplicity. This work presents three-dimensional models mimicking the Bouligand structures by turning the pitch angle of the layers and a analytical models comparison were made. The specimens were fabricated using the FDM technique. A thermoplastic polyurethane (TPU) was used for the matrix and polylactic acid (PLA) for the fibers. Tensile tests were used to mechanically characterize both the raw materials and the manufactured composites to examine the impact of the helical angle and the contribution of the matrix and fiber materials to the stiffness and toughness of the composite. Experiments and analysis revealed that high rotation angles improve the stiffness, strength, and toughness of the composite.