Abstract
In this study, the influence of the open bath and closed-injection pultrusion (CIP) processing methods of epoxy resins on the quality of glass fiber composites was investigated. In addition to the state-of-the-art epoxy resin system with long pot life, new resin systems with short pot life have recently been developed. These systems require processing by closed-injection pultrusion. The epoxies with long pot life allow both processing variants. The experimental work was carried out with two types of injection and impregnation chambers (ii_chamber), namely with a conical and a teardrop design. Fully impregnated composites, which were used for further analyses, could be produced by using the conical ii_chamber. The composite properties of the open bath and the conical ii_chamber impregnation methods were compared. No significant influence on the bending stress could be determined; the interlaminar shear strength was up to 10% better with open bath impregnation than with ii_chamber. For the composites investigated, it was shown that the open bath and ii_chamber impregnation methods can be used to produce parts with partially comparable properties, as demonstrated for the epoxy formulation with long pot life. These results indicate that processing of epoxy systems with a short pot life is also possible by closed-injection pultrusion. Furthermore, the influence on the composite properties of the time interval between the mixing of an epoxy resin and processing in an open bath was investigated. No significant effect on the bending stress and interlaminar shear strength could be determined.
Highlights
The pultrusion process is an established manufacturing method for obtaining high-quality fiber-reinforced plastic (FRP) profiles with constant high mechanical properties and offers additional advantages such as high productivity and comparatively low investment costs
This study investigated the influence of different impregnation methods on the pultrusion process for anhydride curing epoxy resins
The time interval between mixing and processing of the resin was studied for the open bath impregnation case
Summary
The pultrusion process is an established manufacturing method for obtaining high-quality fiber-reinforced plastic (FRP) profiles with constant high mechanical properties and offers additional advantages such as high productivity and comparatively low investment costs. By employing closed-injection pultrusion (CIP), highly reactive amine curing epoxy systems with a short pot life of only a few minutes can be used The processing of these highly reactive resin systems is not yet widespread. Other influencing factors that are frequently investigated in further studies—besides the pulling speed—are the fiber volume fraction (FVF), curing temperature, reaction kinetics with resin shrinkage and the compression ratio at the injection point [16,18]. The influence of the time span between the mixing and use of the resin system in the open bath impregnation system on the mechanical performance of the composite profiles was investigated. The influence of different pulling-speeds on the mechanical characteristics of the pultrudates was investigated
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