Latest carbon fiber reinforced plastics technology: Automotive World 2017

Trunk lid made from a CFRP and foam resin composite material (exhibited by Sekisui Plastics)

  Automotive World 2017 was held in January 2017 at Tokyo Big Site. This report will focus primarily on the exhibitions for The 7th Automotive Lightweight Technology Expo, which was held as part of the event.

  What stood out among the exhibitions were the technical displays of carbon fiber reinforced plastics (CFRP), with each booth drawing large crowds.

  Sekisui Plastics and Asahi Kasei showcased materials sandwiching foam resin with CFRP. Although the materials are thicker than ones singularly made from CFRP, they are being promoted as a lighter material.

  Ichimura Sangyo, part of the Toray Group, exhibited samples of processed carbon fiber-reinforced thermo plastics (CFRTP) that use carbon fiber fabrics and can be stamped. Suncorona Oda showcased CFRTP materials called CFRTP random (non-continuous isotropic) sheets, which are easy to process. Additionally, ARRK exhibited suspension arm parts made from CFRTP, Asano showcased molded items combining CFRTP and aluminum, and Ube Exsymo displayed laminated products using CFRTP materials.

  To summarize the comments from the representatives at each booth, in order for CFR(T)P to be used as a material for automobile parts, there are still many issues that need to be cleared. As processing techniques for mass production are still being developed and established, the issues that remain are the costs of the materials, the lack of empirical evidence to prove their effectiveness, and the need to train technicians that can design and produce parts using CFR(T)P materials.

Related report:
JSAE Exposition 2016: CFRP application trends in Europe (Jul. 2016)
Recent trends in CFRP development: Increased usage in European vehicles (Jul. 2015)
Carbon fiber reinforced thermoplastics and high-tensile steel sheet processing (Mar. 2015)

  Sekisui Plastics exhibited the Techfoamer material it developed, which sandwiches foamed materials between CFRP materials. Techfoamer has the high elasticity, rigidity, and thermal stability of CFRP, while also offering the shaping flexibility, lightweight attributes, and impact absorption of the foamed material at its core. Moreover, being a composite material using CFRP and foamed materials, Techfoamer also has high vibration-damping and thermal insulation properties.

  For example, when ten layers of CFRP with a thickness of 2 mm and Techfoamer S Grade (two layers of CFRP, foamed sheet, and two layers of CFRP, totaling a thickness of 3 mm) at the same size are compared, Techfoamer has rigidity that is three times greater than that of CFRP materials, and is nearly 20% lighter. Additionally, Techfoamer has flexural strength that is three times stronger than that of aluminum while weighing roughly the same. At the same time, Techfoamer F Grade has 8.5 times the thickness of aluminum, and the B Grade has triple the thickness. Techfoamer is still in the sample shipments stage.

Techfoamer grades

Source: Created from Sekisui Plastics documents.

Molded part (trunk lid) made from Techfoamer F Grade	Molded part made from B Grade material
Molded part made from S Grade material	CFRP parts made with pultrusion forming were also exhibited.

  Asahi Kasei developed a composite material that sandwiches Sunforce denatured PPE foam beads between two pieces of CFRP. The company exhibited a molded item made to look like a transmission oil pan that was formed by Sanko Gosei Ltd. In comparison to singular CFRP with equal strength, it is 25% lighter, and uses only 1/5 the CFRP material, while at the same time having double the thickness due to having foamed materials inside.

Asahi Kasei: SunForce denatured PPE foam beads and CFRP composite material	Weight comparison by material (Comparison of material weights of materials with a 20 mm width, 100 mm fulcrum distance, 50 N load, and 1 mm deflection)

  Ichimura Sangyo, a Toray Group company, sells carbon fiber fabrics and composites. At this exhibition, the company exhibited examples of processed items that use carbon fiber stampable sheets (CF-SS), or carbon fiber fabric impregnated with various thermoplastic resins. CF-SS are processed by being heated and dissolved with infrared light and other heating methods, press molded, and then cooled. Processing takes roughly one minute. The exhibited items were processed by equipment and processing manufacturers that Ichimura Sango has cooperative relationships with, such as Asano (see below). Samples of CF-SS have been shipped since 2014.

  According to Ichimura Sangyo, CFRTP has an advantage over thermosetting resins in that it is easy to use it to create hybrid molded parts with other resins, recycling is simple, and store. At the same time, CFRTP has drawbacks. For example, it is not as strong as thermosetting resins; it is still unproven in terms of the development of processing techniques for mass production; it has not been used in automotive parts; and there are few technicians that design parts using CFRTP.

Seat brackets made from a hybrid combination of CF-SS and pellets (ribbed section).

General characteristics of CF-SS

Source: Created based on Ichimura Sangyo's explanatory panel
* Flexural strength measurement test piece processing conditions (using heated and water-cooled press): Material is preheated for 10 minutes at the recommended processing temperature. It is then pressurized for 1 minute at 5 Mpa while still hot. While still under pressure of 5 Mpa, the material is rapidly cooled to 50 degrees, after which it is removed from the mold.

  Suncorona Oda exhibited CFRTP random (non-continuous isotropic) sheets. Short carbon fiber tape, pre-impregnated with resin, was scattered in various directions, and layered (approximately 20 layers) to create a sheet.

  Because many short fibers are layered in different directions, CFRTP random (non-continuous isotropic) sheets have a high mold compliance and transferability. Although they have the same strength as CFRTP sheets based on carbon fiber fabrics, they have higher formability. However, because CFRTP random (non-continuous isotropic) sheets require many manufacturing processes, they are more expensive.

  CFRTP random (non-continuous isotropic) sheets are scheduled for release in April 2017.

CFRTP random sheet	Prepreg tape with a thickness of 50 μm is used as the material for the sheets on the left.
Molded materials made from CFRTP random sheets. Aperture depth is roughly 50 mm. Takt time required for molding is 1 minute.	Complex ribs such as those in the molded part in this photograph can also be made.

Source: Created based on Suncorona Oda's explanatory documents

  ARRK, a company that helps develop new products for automobiles, exhibited prototype suspension arms made from CFRTP that are based on steel (590 MPa) suspension arms featured in current European vehicles, but perform at equal levels. Steel suspension arms weigh 2.4 kg, but use of the CFRTP suspension arms enables 38% weight reduction to 1.5 kg.

  According to an ARRK representative, a 38％ reduction in weight is roughly equivalent to the weight of aluminum suspension arms, and ARRK aims to achieve a 50% weight reduction in comparison to steel. Currently, the company is working to make the material take advantage of all of the advantages of existing composite materials as ARRK's CFRTP material still has numerous areas that have a certain thickness and are excessively strong. One method ARRK is investigating to resolve this issue is applying ribs to make these areas thinner.

  Asano exhibited a beam made from the CFRTP composite material sandwiched by aluminum plates. The exhibited item was made from press-molded aluminum adhered to a CFRTP molded part. By using some CFRTP, strength can be increased where necessary, and weight reduced further.

  Ube Exsymo, a fully owned subsidiary of Ube Industries, is currently developing a laminated material in which carbon fiber materials are sandwiched by thermoplastic resin. At this exhibition, the company put samples on display. Ube Exsymo is considering proposing use of the materials in areas where strength is necessary. The material is characterized by its long sheet and ability to be produced continuously.

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Keyword
CFRP, CFRTP, reinforced resin, Carbon fiber

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