In the automobile industry, reduction of car weight is needed to deal with environmental issues. Recently, Carbon Fiber Reinforced Plastics (CFRP) is expected to be used for lightweight component parts. The application of CFRP will become possible to reduce car weights, because CFRP has higher specific strength and specific rigidity. However the cost of CFRP is so high that the use of CFRP does not increase. In addition, it is expected to use thermoplastics as a matrix of CFRP in consideration of recyclability. To mold Carbon Fiber Reinforced Thermoplastics (CFRTP), it is necessary to impregnate carbon fiber with thermoplastic resin by heating the materials. There are electromagnetic induction heating and direct resistance heating for heating method. The electromagnetic induction heating has a high production cost because of complicated equipment. On the other hand the direct resistance heating is performed with a simple piece of equipment and low consumed power. It is better to use direct resistance heating for low-cost CFRTP molding. We propose a method of CFRTP molding process using direct resistance heating of carbon fibers in n on crimp fabric (NCF). In this paper, the resistance heating characteristic of NCF and the influence of resistance heating upon mechanical properties of carbon fiber were discussed. The temperature distribution of 0° and 90° layer were sufficient and it took 70s to reach to 250°C on temperature history when heat is applied to the NCF [0°/90°] using direct resistance heating. From the results of tensile tests of single carbon fiber, tensile strength was not decreased by resistance heating at 300°C for 300s.

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.

Carbon Fibre Reinforced Plastics (CFRP) with thermo-setting resin are usually used in aerospace applications and racing cars. However, considering moulding time and recyclability, it is desirable to use thermoplastics resin for the matrix. In our previous study, Non-woven Stitched Multi-axial Cloth (NSMC) was developed as moulding semi-product of Carbon Fibre Reinforced Thermoplastics (CFRTP). In this study, the rapid pipe moulding process of CFRTP components by means of high-frequency direct resistance heating, in combination with NSMC, was invented. This method allows heating of the mould surface rapidly by using high-frequency direct resistance heating. NSMC makes the lamination process easy, due to the fact that the non-crimp fabric of carbon fibre and the non-woven fabric of thermoplastics resin are stitched to one sheet, so production cycle time can be reduced. The invented high-speed moulding technique is expected to apply to CFRTP pipes. This moulding method can also reduce production cycle times, and therefore the cost to manufacture composite parts can also be reduced. CFRTP pipe had been successfully moulded in the size of 300 mm in length, 47 mm in diameter and 3 mm in thickness by this moulding method.

In the automobile industry, from the point of preventing global warming, the mass reduction of automotive bodies has become more important than ever. Especially automotive weight lightening by using Carbon Fiber Reinforced Thermoplastics (CFRTP), which has advantage of high-specific strength and high-specific modulus, has received much attention. A lot of pipe-shaped materials are used for a car. For CFRTP pipe molding, a low-cost and high-speed molding method is required. Using high-frequency electric resistance heating allows heating the mold surface rapidly. Rapid heating of the mold can reduce production cycle time. The electrical energy of this heating method is less than that of traditional heating methods, and therefore the reduction in production cost is expected. In molding of CFRTP, uniformity of temperature distribution is one of the important issues to be solved. In this study, temperature distribution of CFRTP pipe molding by direct resistance heating was evaluated by FEM analysis. In direct resistance heating, the temperature distribution of the mold depends on the shape of electrodes and electric frequency. Influence of the shape of electrodes and electric frequency on the temperature distribution of the mold is revealed by using FEM analysis.

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