Development of Rapid Pipe Moulding Process for Carbon Fiber Reinforced Thermoplastics by Direct Resistance Heating

Abstract

To deal with environmental issues, the gasoline mileage of passenger cars can be improved by reduction of the car weight. The use of car components made of Carbon Fiber Reinforced Plastics (CFRP) is increasing because of its superior mechanical properties and relatively low density. Many vehicle structural parts are pipe-shaped, such as suspension arms, torsion beams, door guard bars and impact beams. A reduction of the car weight is expected by using CFRP for these parts. Especially, when considering the recyclability and ease of production, Carbon Fiber Reinforced Thermoplastics are a prime candidate. On the other hand, the moulding process of CFRTP pipes for mass production has not been well established yet. For this pipe moulding process an induction heating method has been investigated already, however, this method requires a complicated coil system. To reduce the production cost, another system without such complicated equipment is to be developed. In this study, the pipe moulding process of CFRTP using direct resistance heating was developed. This heating method heats up the mould by Joule heating using skin effect of high-frequency current. The direct resistance heating method is desirable from a cost perspective, because this method can heat the mould directly without using any coils. Formerly developed Non-woven Stitched Multi-axial Cloth (NSMC) was used as semi-product material. NSMC is very suitable for the lamination process due to the fact that non-crimp stitched carbon fiber of [0°/+45°/90°/-45°] and polyamide 6 non-woven fabric are stitched to one sheet, resulting in a short production cycle time. The use of the pipe moulding process with the direct resistance heating method in combination with the NSMC, has resulted in the successful moulding of a CFRTP pipe of 300 mm in length, 40 mm in diameter and 2 mm in thickness.

CFRTP pipe molding process using high-frequency direct resistance heating

“…The ratio to each expected value was 95% and 89%. The tensile strength and the tensile modulus of the pipe, which was directly molded with NSMC and nonwoven resin fabric, were reported to be 427 MPa and 26.4 GPa respectively in previous study [6]. By using the prepreg sheet for pipe molding, better quality pipe can be manufactured.…”

“…For the production of references, NSMC and nonwoven fabric instead of prepreg sheet was used for CFRTP pipe molding as shown in the previous study [6].…”

“…Sheet winding method has an advantage that its production cycle time is shorter than that of filament winding method [5]. In previous studies, CFRTP pipe was produced by using Non-woven Stitched Multi-axial Cloth (NSMC) as semi-product material of CFRTP in sheet winding method [6]. NSMC is sheet-shaped intermediate material for CFRTP that was made by stitching carbon fibers and nonwoven matrix resin simultaneously in the process of manufacturing non-crimp stitched fabric (NCF).…”

“…Although CFRTP pipe mold was heated rapidly by using high-frequency direct resistance heating, molded CFRTP pipe has tensile strength of 427 MPa that was 70% of the expected value [6]. Impregnating and shaping processes were performed at the same time for the purpose of shortening the molding time.…”

FEM analysis of the temperature distribution of CFRTP pipe mold with direct resistance heating

“…With this method, electric current passes near the mold surface intensively by skin effect and heats the mold by Joule heating. Direct resistance heating can reduce cost by the simplification of facilities in comparison with the induction heating method and to improve energy efficiency [3,4]. However, direct resistance heating method has a drawback regarding the temperature distribution of the mold.…”