This study focuses on the evaluation of the effect of hygrothermal conditioning on tensile, compressive, in-plane and interlaminar shear properties, and also on the viscoelastic characteristics of carbon fiber/epoxy laminates. Flat unidirectional laminates were manufactured by dry filament winding and cured under hot compression. The laminates were later exposed to hygrothermal conditioning in a chamber, following the recommendations of ASTM D5229M. All composite coupons were tested before and after conditioning. An analytical Fickian model was used to fit experimental data, showing very good estimates. Shear strength and modulus reduced to about 30 and 38 %, respectively. All specimens presented acceptable failure modes; shear specimens failed at the gage section with delaminations and fiber/matrix debonding, whereas short beam specimens failed via delaminations at the specimen mid-plane. Moisture penetration through the carbon/epoxy surface lead to interfacial debonding and matrix plasticization. Puck's failure envelope accurately predicted failure under compressive and shear loading.

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An experimental investigation of the resistance welding of PPS/carbon fiber is presented in this manuscript. Currently, one of the main problems of the structural polymer composites consists in its effective integration of the components. The electrical resistance welding has been considered as one of the promising techniques for bonding composites, because it is a quick process with easy surface preparation. To improve the process to welding poly-(phenylene sulfide) (PPS) reinforced with carbon fiber laminates, it was used a full factorial design (23). Considering the factors pressure, electrical current and time, the more appropriate conditions for welding were evaluated based on a criterion of maximum lap shear strength, according to ASTM D1002-10. A comparison between welded and non-welded specimens in terms of analysis dynamic mechanical (DMA), thermomechanical analysis (TMA) and vibration tests was performed. It was demonstrated that large-scale DMA presented a similar results but according to TMA and vibration test were observed that welded specimens presented different results when compared to non-welded laminates, due probably to the presence of metallic heating element.

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This study aims to reuse the waste of uncured composite prepreg scraps from the ply cutting manufacturing process in the aerospace industry, avoiding the resin loss, waste disposal and expenses with its incineration.Carbon fiber/F155-epoxy resin laminates were produced by randomly positioned scraps, with different sizes and shapes, and characterized by tensile, compression, interlaminar shear (ILSS), and flexural tests. Tensile, compression, and flexural strengths of produced laminates decreased 13, 23, and 56%, respectively, compared to the same prepreg references. The ILSS test showed results 34% higher compared to the references. Higher specific strength (compression and tensile) was found in relation to a typical aircraft aluminum alloy. Therefore, the results opens a potential path to reuse uncured prepreg composite scraps to produce artifacts, as mold structures used in composites manufacturing, reducing the waste disposal in nature and contributing to sustainability.

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