No abstract

Advanced thermoplastic composites are an alternative because of their ease of processing and storage. Poly(phenylene sulfide) (PPS) stands out among these materials because of its structural characteristics; for instance, it provides size, shape, and thermal stability, low moisture absorption, excellent chemical resistance, and good mechanical properties, including flexure, strength, and shear properties, compared to thermoset composites. Thus, the objective of this study was to evaluate the influence of environmental conditioning on the shear strength behavior of PPS/glass fiber composites. For this reason, first, some samples were treated to UV-light exposure in a chamber. Other samples were immersed in seawater and hygrothermal baths simultaneously. They were tested with the interlaminar shear strength (ILSS) and Iosipescu shear test methods. The shear values obtained for the treated samples were compared against the dry sample values. For all samples tested with the ILSS and Iosipescu methods, the results indicate that the PPS/glass fiber composites presented a decrease in shear strength after they were submitted to hygrothermal and seawater solution conditioning. The moisture absorption was not uniform throughout the material, and wet conditioning induced strong matrix plasticization, which reduced the shear strength values of the laminates.

Resumo: Os compósitos termoplásticos avançados são uma alternativa a compósitos termorrígidos em algumas aplicações aeronáuticas, devido a ganhos em propriedades. Dentre as matrizes termoplásticas, o PPS (poli sulfeto de fenileno) destaca-se devido às suas características estruturais. O objetivo deste trabalho é avaliar a influência do condicionamento ambiental sobre o comportamento de resistência ao cisalhamento de PPS / fibras de carbono. Por esta razão, amostras deste material foram condicionadas em solução salina, em banho higrotérmico e sob radiação UV. Após estes condicionamentos os corpos-de-prova foram avaliados quanto a sua resistência aos cisalhamentos interlaminar (ILSS) e Iosipescu e os resultados obtidos foram comparados. Quando comparado ao valor de cisalhamento interlaminar obtido do compósito não-climatizado (58,4 ± 1,9 MPa), os valores de cisalhamento interlaminar ILSS decaíram em torno de 14 e 3%, respectivamente, após banho higrotérmico e banho salino. Sob condicionamento por radiação UV houve um decréscimo de 2% após exposição por 300 horas, 11% após 600 horas e 9% após 900 horas. Já o laminado ensaiado pelo método Iosipescu teve uma tensão de cisalhamento no plano de 109,2 ± 0,4 MPa. Com condicionamentos, teve um decréscimo de 6% após banho higrotérmico e 12% após banho salino. A exposição à radiação UV provocou na resistência de cisalhamento no plano um decaimento de 6% para o condicionamento de 300 horas, 10% para o condicionamento de 600 horas e 14% para o condicionamento por 900 horas. Palavras-chave: Poli sulfeto de fenileno (PPS), fibra de carbono, propriedades de cisalhamento, compósito termoplásticos, condicionamento ambiental. Effect of Environmental Degradation on Shear Properties of PPS /Carbon Fiber CompositesAbstract: Advanced thermoplastic composites are an alternative to thermoset composites in many aeronautical applications owing to their superior properties. Among the thermoplastic matrix, PPS (poly phenylene sulfide) stands out due to its structural characteristics. The objective of this study is to evaluate the influence of environmental conditioning on the shear behavior of PPS / carbon fiber composites. Samples of this material have been conditioned in saline water solution, in hygrothermal conditioning and under UV radiation. After conditionings the specimens were evaluated by interlaminar shear strength (ILSS) and Iosipescu shear test methods. The environmental conditioning reduced the interlaminar shear stress (ILSS) of conditioned composites in comparison with non-conditioned composites tested with the same method (58.4 ± 1.9 MPa). The ILSS decreased by ca. 14 and 3%, respectively, after hygrothermal conditioning and saline water solution. Moreover, the values of interlaminar shear stress under UV radiation decreased by 2, 11 and 9% after exposure times of 300, 600 and 900 hours, respectively. The non-conditioned composites tested with the Iosipescu method (109.2 ± 0.4 MPa ) also had ILSS decreasing with environmental conditioning: the values decreased 6% after hygro...