Influence of power ultrasonic on the impregnation of unidirectional fibers in closed injection pultrusion

The influence of power ultrasonic (US) on the closed injection pultrusion is investigated in a real test environment. For this purpose, the US is directly integrated into the impregnation chamber of a pultrusion die. The chamber geometry is designed according to the patent of Koppernaes et al. A pure unidirectional reinforcement of glas fibers (SE 3030, 4800 tex, 3B, Belgium) and carbon fibers (C T50-4.0/240-E100, SGL Carbon SE, Germany) is used as laminate structure in combination with an epoxy resin system (Biresin CR141, Sika, Germany). Additional temperature control channels are integrated into the impregnation chamber in order to extract the temperature\u0027s influence. The following variables are investigated: Ultrasonic amplitude, position of US-coupling and temperature. Mechanical parameters (3-point bending, ILSS) are determined and macroscopic images are examined. The investigation indicates that US can slightly increase the mechanical parameters. However, the same effect is achieved when tempering the impregnation system. Therefore, the effect of viscosity reduction is solely due to the temperature increase. The coupled power\u0027s upper limit is determined by the fiber, not the matrix. An acoustic sonication of the fibers with an US amplitude too high destroys the fibers. In summary, US has a positive influence on the impregnation performance during pultrusion. However, the effect can be directly attributed to the resulting temperature increase of the matrix. Instead of excitation via US, a similar effect can also be achieved by temperature control of the impregnation system.