Ablative Properties of Polyurethanes Reinforced with Organoclay

Ablation resistance and mechanical properties of polyurethanebased composites containing different amounts (up to 5 wt%) of organoclay were correlated with the morphological characterization. The crosslinking density of the polyurethane increased with the amount of organoclay. At low concentration (up to 1 wt%), the organoclay was well exfoliated, while at higher concentration, both exfoliated and intercalated platelets were found. A linear correlation was observed between the tensile test and the concentration of organoclay. Erosion velocity decreased 40% with the incorporation of 5% of organoclay.Fil: Bocchio, Javier Andres. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; ArgentinaFil: Escobar, Mariano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Industrial; ArgentinaFil: Quagliano Amado, Javier Carlos. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin

Avaliação da temperatura de transição vítrea de compósitos poliméricos reparados de uso aeronáutico Evaluation of glass transition temperature of the repaired polymeric composites of aeronautical use

Este trabalho mostra a avaliação da temperatura de transição vítrea (Tg), por DMTA, de três famílias de compósitos poliméricos reparados, tendo como laminados base tecidos de fibras de carbono/resina epóxi modificada com elastômero (F584), vidro/resina epóxi (F161) e aramida/resina epóxi (F161). Os compósitos foram laminados manualmente por processo convencional e curados em autoclave de indústria aeronáutica. Posteriormente, danos foram simulados sendo, em seguida, reparados adotando-se a técnica de sobreposição de camadas de pré-impregnados de resina epóxi (F155), com adição de filme adesivo de epóxi (FM 73). As curvas DMTA mostram os efeitos da combinação de diferentes sistemas de resinas na Tg e, conseqüentemente, na temperatura de serviço do componente reparado. O material de reparo utilizado, baseado em pré-impregnados com resina epóxi F155 e filme adesivo de epóxi, provocou a redução da Tg dos compósitos reparados. Para os laminados base com tecido de fibras de carbono e vidro foram verificadas reduções de aproximadamente 30 °C na Tg. Este efeito foi mais pronunciado (redução de aproximadamente 40 °C) quando o laminado reparado de aramida foi submetido a condicionamento higrotérmico a temperatura e umidade elevadas. Esta redução na Tg dos laminados reparados é atribuída à migração do adesivo para o pré-impregnado de resina epóxi F155 utilizado no reparo, durante o processo de cura, e à plasticização do sistema polimérico pela água, durante o condicionamento higrotérmico. A redução da Tg leva a uma conseqüente redução da temperatura de serviço do compósito polimérico reparado.<br>This work shows the evaluation of the glass transition temperature (Tg) by DMTA of three different families of repaired polymeric composites, manufactured with carbon fiber fabric/epoxy F584, glass fabric/epoxy F161 and aramide fabric/epoxy F161, respectively. The composites were laminated by conventional hand lay-up process used in aeronautical industry. Afterwards, simulated damages, scarf type, were made and overlapping layers of F155 epoxy resin prepregs repaired them. The DMTA curves show the effects of combination of different systems resins on the Tg values and, consequently, on the service temperature of the repaired laminate. The used repairing material (based on epoxy resin F155 and on epoxy adhesive film FM73) decreased the Tg of the repaired laminates in approximately 30 °C for the carbon and glass laminates. The conditioning of aramide laminate under elevated humidity and temperature provoked a more decrease of the Tg (reduction of approximately 40 °C). The Tg reduction for the repaired laminates is attributed to the adhesive film migration into the F155 resin system during the cure process and also to the resin plasticization by water diffusion during the hygrothermal conditioning. The Tg reduction leads to a decrease of the service temperature of the repaired polymeric composite

Performance of the joint LST-1 and MAGIC observations evaluated with Crab Nebula data

International audienceAims. LST-1, the prototype of the Large-Sized Telescope for the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning in Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 (Large-Sized Telescope 1) to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes permits observations of the same gamma-ray events with both systems. Methods. We describe the joint LST-1+MAGIC analysis pipeline and use simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results. Thanks to the resulting increase in the collection area and stronger background rejection, we find a significant improvement in sensitivity, allowing the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range ~60 GeV to ~10 TeV, is in agreement with previous measurements

Performance of the joint LST-1 and MAGIC observations evaluated with Crab Nebula data

International audienceAims. LST-1, the prototype of the Large-Sized Telescope for the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning in Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 (Large-Sized Telescope 1) to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes permits observations of the same gamma-ray events with both systems. Methods. We describe the joint LST-1+MAGIC analysis pipeline and use simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results. Thanks to the resulting increase in the collection area and stronger background rejection, we find a significant improvement in sensitivity, allowing the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range ~60 GeV to ~10 TeV, is in agreement with previous measurements

Performance of the joint LST-1 and MAGIC observations evaluated with Crab Nebula data

International audienceAims. LST-1, the prototype of the Large-Sized Telescope for the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning in Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 (Large-Sized Telescope 1) to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes permits observations of the same gamma-ray events with both systems. Methods. We describe the joint LST-1+MAGIC analysis pipeline and use simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results. Thanks to the resulting increase in the collection area and stronger background rejection, we find a significant improvement in sensitivity, allowing the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range ~60 GeV to ~10 TeV, is in agreement with previous measurements