Advanced composites are extremely strong, rigid, and light, even when compared with advanced metals. Advanced composites are replacing high-tech metals as the material of choice for aerospace engineering. However, the processes used to manufacture advanced composites generally lose some of the properties of the materials by their process limitations. One process that keeps the theoretically awesome qualities of the composite materials in tact is filament winding. Filament wound parts are used as rocket shells, bicycle frame tubes, drive shafts, pressure vessels, etc. Filament winding is an automated process and makes reliable parts to close tolerances. If a straight tube were to be made by all the existing composites manufacturing processes, filament wound tubes would be significantly better than any other. However, filament winding is generally limited to making straight tubes. A new process based on filament winding is proposed; one that can wind complex shapes of the same high quality as conventional filament winding. This process has achieved this by winding continuous, uncut, and aligned fibers. This process is called Lotus Filament Winding.

O uso de nanotubos de carbono (NTC) em compósitos Epóxi (EP)/Fibra de Vidro (FV), produzindo compósitos tri-componente, tem sido recentemente pesquisado, com alguns resultados interessantes relacionados a propriedades mecânicas e eletromagnéticas. Para que haja uma promoção mais significativa nas propriedades mecânicas, deve-se introduzir um teor de NTC maior do que 1% em massa, o que gera graves problemas de dispersão. O grande desafio de trabalhar com um elevado de NTC, é que a viscosidade da resina é significativamente aumentada em relação à resina pura, dificultando a dispersão e o processamento dos compósitos. Foi desenvolvida neste trabalho uma metodologia para dispersão de NTC em tecidos de FV, buscando aumentar os teores de NTC em compósitos tri-componente EP/NTC/FV e produzidos por moldagem por transferência de resina (RTM). Os compósitos tri-componente foram caracterizados por meio de ensaios mecânicos como tração, flexão, impacto Izod, cisalhamento interlaminar (ILSS), dureza Barcol e da análise dinâmico-mecânica (DMA); além da inspeção por ultrassom e avaliação da atenuação da radiação eletromagnética. Os compósitos apresentaram um aumento aproximado de 10% nas propriedades mecânicas, porém mostrando um maior potencial com relação à atenuação eletromagnética, onde alcançaram valores de absorção de ondas de até 95%. / The use of carbon nanotubes (CNT) in Epoxy (EP)/Glass Fiber (GF) composites, producing tri-component composites, has been widely researched, with some interesting results related to mechanical and electromagnetic properties. When the goal is a significant improvement in mechanical properties, CNT content greater than 1%wt. may be necessary, which yields serious dispersion problems. The great challenge when processing a high CNT content resin is that its viscosity is significantly increased in comparison with the neat resin, preventing adequate dispersion and processing of the composite. In this work, a methodology for the dispersion of CNT in GF fabrics was developed aiming to increase the CNT content in EP/CNT/GF tri-component composites produced by resin transfer molding (RTM). The composites were characterized using tensile, flexural, Izod impact, interlaminar shear strength (ILSS), Barcol hardness testing and dynamic mechanical analysis (DMA); ultrasound inspection and attenuation of electromagnetic radiation evaluation were also carried out. The tri-component composites showed an overall maximum increase of only 10% in the mechanical properties, but displayed great potential use for attenuation of electromagnetic radiation, reaching 95% wave absorption.

O uso de nanotubos de carbono (NTC) em compósitos Epóxi (EP)/Fibra de Vidro (FV), produzindo compósitos tri-componente, tem sido recentemente pesquisado, com alguns resultados interessantes relacionados a propriedades mecânicas e eletromagnéticas. Para que haja uma promoção mais significativa nas propriedades mecânicas, deve-se introduzir um teor de NTC maior do que 1% em massa, o que gera graves problemas de dispersão. O grande desafio de trabalhar com um elevado de NTC, é que a viscosidade da resina é significativamente aumentada em relação à resina pura, dificultando a dispersão e o processamento dos compósitos. Foi desenvolvida neste trabalho uma metodologia para dispersão de NTC em tecidos de FV, buscando aumentar os teores de NTC em compósitos tri-componente EP/NTC/FV e produzidos por moldagem por transferência de resina (RTM). Os compósitos tri-componente foram caracterizados por meio de ensaios mecânicos como tração, flexão, impacto Izod, cisalhamento interlaminar (ILSS), dureza Barcol e da análise dinâmico-mecânica (DMA); além da inspeção por ultrassom e avaliação da atenuação da radiação eletromagnética. Os compósitos apresentaram um aumento aproximado de 10% nas propriedades mecânicas, porém mostrando um maior potencial com relação à atenuação eletromagnética, onde alcançaram valores de absorção de ondas de até 95%. / The use of carbon nanotubes (CNT) in Epoxy (EP)/Glass Fiber (GF) composites, producing tri-component composites, has been widely researched, with some interesting results related to mechanical and electromagnetic properties. When the goal is a significant improvement in mechanical properties, CNT content greater than 1%wt. may be necessary, which yields serious dispersion problems. The great challenge when processing a high CNT content resin is that its viscosity is significantly increased in comparison with the neat resin, preventing adequate dispersion and processing of the composite. In this work, a methodology for the dispersion of CNT in GF fabrics was developed aiming to increase the CNT content in EP/CNT/GF tri-component composites produced by resin transfer molding (RTM). The composites were characterized using tensile, flexural, Izod impact, interlaminar shear strength (ILSS), Barcol hardness testing and dynamic mechanical analysis (DMA); ultrasound inspection and attenuation of electromagnetic radiation evaluation were also carried out. The tri-component composites showed an overall maximum increase of only 10% in the mechanical properties, but displayed great potential use for attenuation of electromagnetic radiation, reaching 95% wave absorption.

O uso de nanotubos de carbono (NTC) em compósitos Epóxi (EP)/Fibra de Vidro (FV), produzindo compósitos tri-componente, tem sido recentemente pesquisado, com alguns resultados interessantes relacionados a propriedades mecânicas e eletromagnéticas. Para que haja uma promoção mais significativa nas propriedades mecânicas, deve-se introduzir um teor de NTC maior do que 1% em massa, o que gera graves problemas de dispersão. O grande desafio de trabalhar com um elevado de NTC, é que a viscosidade da resina é significativamente aumentada em relação à resina pura, dificultando a dispersão e o processamento dos compósitos. Foi desenvolvida neste trabalho uma metodologia para dispersão de NTC em tecidos de FV, buscando aumentar os teores de NTC em compósitos tri-componente EP/NTC/FV e produzidos por moldagem por transferência de resina (RTM). Os compósitos tri-componente foram caracterizados por meio de ensaios mecânicos como tração, flexão, impacto Izod, cisalhamento interlaminar (ILSS), dureza Barcol e da análise dinâmico-mecânica (DMA); além da inspeção por ultrassom e avaliação da atenuação da radiação eletromagnética. Os compósitos apresentaram um aumento aproximado de 10% nas propriedades mecânicas, porém mostrando um maior potencial com relação à atenuação eletromagnética, onde alcançaram valores de absorção de ondas de até 95%. / The use of carbon nanotubes (CNT) in Epoxy (EP)/Glass Fiber (GF) composites, producing tri-component composites, has been widely researched, with some interesting results related to mechanical and electromagnetic properties. When the goal is a significant improvement in mechanical properties, CNT content greater than 1%wt. may be necessary, which yields serious dispersion problems. The great challenge when processing a high CNT content resin is that its viscosity is significantly increased in comparison with the neat resin, preventing adequate dispersion and processing of the composite. In this work, a methodology for the dispersion of CNT in GF fabrics was developed aiming to increase the CNT content in EP/CNT/GF tri-component composites produced by resin transfer molding (RTM). The composites were characterized using tensile, flexural, Izod impact, interlaminar shear strength (ILSS), Barcol hardness testing and dynamic mechanical analysis (DMA); ultrasound inspection and attenuation of electromagnetic radiation evaluation were also carried out. The tri-component composites showed an overall maximum increase of only 10% in the mechanical properties, but displayed great potential use for attenuation of electromagnetic radiation, reaching 95% wave absorption.

Recent research and development has resulted in a working prototype of an automated process for manufacturing IsoTruss® and other innovative open lattice composite structures which yields faster, and more predictable and consistent parts, while automatically consolidating individual members. This machine is sufficiently versatile to manufacture any type of open lattice structure fabricated from filamentary composite materials. The objectives of the research in this thesis were two-fold: (1) to validate this new process for making IsoTruss structures; and (2) to measure the compression strength and stiffness of specimens produced on the machine. In order to accomplish the first purpose, various parts were manufactured on this prototype machine, including: a six-node IsoTruss structure with single outer longitudinal members, a three-longitudinal member section of an inner longitudinal IsoTruss structure with consolidated members, and a two-bay IsoTruss panel structure. By creating and running patterns to make these parts, the hypothesis that the machine will make any geometry of IsoTruss structure was validated. The second objective of this research was accomplished by testing the compression strength and stiffness of specimens manufactured with this automated process. Buckling versus compression failure of members was examined by varying member aspect ratios. The effect of intersecting helical members was also explored, as was the effect of changing the number of braiding bobbins used to consolidate members. Testing showed that increasing the number of braiders increases consistency of the braided sleeves and reduces scatter in the results. The ratio of helical to longitudinal tows at a joint is directly related to the percent decrease in member strength at the joint. Compression failure of individual members is the preferred method of failure, because this type of failure absorbs significantly more energy. This research proves that the manufacturing process will produce even the most complex IsoTruss geometries, with the necessary consolidation of individual members. Findings also indicate that a few modifications -- such as improved bobbins, more reliable switches, more accurate pulling system, etc. -- will enable this automated process to produce composite lattice structures with superior mechanical properties.