Joule heating of dry textiles made of recycled carbon fibers and PA6 for the series production of thermoplastic composites

Abstract

Processing carbon fiber reinforced thermoplastic parts includes heating to form the thermoplastic matrix. The needed heat can be applied externally or internally to the preform. One possibility to generate intrinsic heat involves the use of carbon fibers as a resistive element to induce joule heat. So far, most research efforts have been based on contacting continuous carbon fibers on both ends to melt the thermoplastic matrix of a pre-impregnated preform. The objective of this project is to use a dry hybrid yarn textile in a one-step process to impregnate and rapidly consolidate the dry textile in less than a minute. The desired molding process is based on joule heating of carbon fibers due to an applied current in the transverse fiber direction. This article focuses on the detection of the involved macroscopic parameters. The first composites produced by means of this new method exhibit a high potential with heating times of 15 s, a void fraction below 1%, and flexural properties comparable to the state of the art.

Characterization of the electrical behavior of a discontinuous hybrid yarn textile made of recycled carbon and PA6 fibers during Joule heating

“…The aim of the process discussed in this article is to use one tool to add heat, pressure, and movement to impregnate and consolidate the semifinished part in a one-step process. First experiments yielded satisfying results for this concept with a void fraction below 1 %, flexural properties in accordance with the state of the art and heating times of 15 s. 11 Further research is required to investigate the theoretic behavior of the changing resistivity in textiles used in the setup depicted in Figure 2. Changes in resistivity may result from the impregnation and consolidation process.…”

“…The further development of the hybrid yarn and the multilayer fabric is described in the literature. 11,21,22…”

“…The samples were prepared by energizing the hybrid yarn textile based on the setup shown in Figure 1 for 5 s, 10 s, 20 s, and 80 s. Measurement data were recorded using a Graphtec logger GL240 in the style of DIN EN 16812 and DIN EN 60584. The setup, dimensions, and equipment are described in Reese et al 11 The research introduced in this article focused on changes in resistivity due to changes in temperature, the degree of compaction, and current. Figure 2 shows two electrodes connected to a direct current (DC) source, which were placed into a pressure-controlled press.…”

“…The suitability of electric current to generate heat in a carbon fiber-based textile, thus forming composite parts, has been proven in the literature. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] First applications of Joule heat in carbon fibers were aimed at the efficient curing of thermoset resins. [1][2][3][4] The resulting cured composites were manufactured with short cycle times while offering identical mechanical behavior to the state of the art.…”

“…1,4 Recently, researchers started to employ the concept of Joule heating for processing pre-impregnated thermoplastic materials. [5][6][7][8][9][10][11] Further developments in this field have since enabled the manufacturing of simple 3D parts from pre-impregnated thermoplastic sheets. Even complicated shapes could be heated evenly throughout the parts.…”