Structural adhesives emerge as an alternative technique for joining materials used in tertiary structures in the oil and gas industry instead of welding, for example, in order to mitigate risks caused by the use of sparks on offshore platforms. Therefore, the present work aims to evaluate the influence of different surface treatments of the adherent material (carbon fiber/epoxy composite) on the mechanical behavior of the adhesive joints through the lap shear test. Furthermore, the viscoelastic properties of the epoxy-based structural adhesive were analyzed via dynamic-mechanical analysis (DMA). The results indicates that the adhesive exhibits residual curing when cured at room temperature and a post-curing process is required to increase its glass transition temperature (Tg) and its stiffness, Lap Shear tests results shows that the adherent surface treatment that generated the best mechanical response was cleaning with solvent, despite its lower roughness compared to the fuseply treatment, which indicates a strong correlation between roughness and wettability in obtaining resistant adhesive joints.

Sickle cell anemia (SCA) causes dysfunction of multiple organs, with pulmonary involvement as a major cause of mortality. Recently, there has been growing interest in the nitrogen single-breath washout (N2SBW) test, which is able to detect ventilation heterogeneity and small airway disease when the results of other pulmonary function tests (PFTs) are still normal. Thus, the objectives of the present study were to assess the heterogeneity in the ventilation distribution in adults with SCA and to determine the association between the ventilation distribution and the clinical, cardiovascular, and radiological findings. This cross-sectional study included 38 adults with SCA who underwent PFTs, echocardiography, computed tomography (CT), and 6-min walk test. To evaluate the ventilation heterogeneity, the patients were categorized according to the phase III slope of the N2SBW (SIIIN2). Compared with adults with lower SIIIN2 values, adults with higher SIIIN2 values showed lower hemoglobin levels (P=0.048), a history of acute chest syndrome (P=0.001), an elevated tricuspid regurgitation velocity (P=0.039), predominance of a reticular pattern in the CT (P=0.002), a shorter 6-min walking distance (6MWD) (P=0.002), and lower peripheral oxygen saturation (SpO2) after exercise (P=0.03). SIIIN2 values correlated significantly with hemoglobin (rs=-0.344; P=0.034), forced vital capacity (rs=-0.671; P<0.0001), diffusing capacity for carbon monoxide (rs=-0.376; P=0.019), 6MWD (rs=-0.554; P=0.0003), and SpO2 after exercise (P=0.040). Heterogeneity in the ventilation distribution is one of the most common pulmonary dysfunctions in adults with SCA. Moreover, relationships exist between ventilation heterogeneity, worsening of pulmonary structural damage, and reduced tolerance for exercise.

A utilização de compósitos poliméricos na fabricação de aeronaves vem sendo cada vez mais intensa. Em função disso, a possibilidade de ocorrer falhas em serviço de um componente fabricado em compósito polimérico torna-se cada vez maior. A análise de falhas de materiais compósitos ainda é um tema pouco explorado, principalmente no Brasil, porém vem tornando-se cada vez mais importante em apoio à área de prevenção e investigação de acidentes aeronáuticos. Este trabalho teve como objetivo a caracterização de fraturas em laminados unidirecionais de fibra de carbono de módulo intermediário com sistema de resina epóxi modificada, tipo 8552, em resistência ao cisalhamento interlaminar nas condições ambiente e saturado de umidade em câmara higrotérmica. A análise fractográfica no plano de falha dos laminados foi realizada por microscopias óptica e eletrônica de varredura. A comparação dos resultados mostrou que o condicionamento higrotérmico afetou significativamente a região de interface da resina sem alterar a adesão interfacial fibra/resina. Os aspectos de fratura presentes na região de resina, como cristas de galo e escarpas, e do reforço foram detalhados, podendo-se assim estabelecer a direção de propagação da trinca e caracterizar o modo de falha, por ser do tipo misto (arrancamento e cisalhamento simultaneamente).

The use of polymeric composites in aircraft fabrication has been more and more intense. As a function of this fact, the possibility to occur service failures in components produced by using polymeric composites has increased more and more. The failure analyses in composite materials is still not much explored, principally in Brazil, but it has been very important in order to give subsidies to prevent aeronautical accidents. This work focuses the fracture characterization of intermediate modulus type unidirectional carbon fiber laminates impregnated with modified epoxy resin (code 8552), by using interlaminar shear test, in two conditions: ambient and saturated with moisture in an hygrothermal chamber. The fractographic analyses on the failure plane of the laminates were performed by optical and scanning electron microscopies. The comparison of results showed that the hygrothermal conditioning affects significantly the interface region but doesn't alter the fiber/matrix interfacial adhesion. The failure modes present in the resin region, such as hackles and scarps, and in the reinforcement were evaluated, being possible to establish the failure propagation direction and the failure mode that was characterized as a mixing of pull-out and shear modes.