The CFRP automobile body project in Japan
Ph.D. Akihiko Kitano
Toray Industries, Inc. Ehime Plant.
General Manager of Composite Materials Research Laboratories
Eisuke Wadahara
Toray Industries, Inc. Ehime Plant.
Senior Research Engineer of Composite Materials Research Laboratories
Ichiro Taketa
Toray Industries, Inc. Ehime Plant.
Research Engineer of Composite Materials Research Laboratories

ABSTRACT"R&D of Carbon Fiber-Reinforced Composite Materials to Reduce Automobile
Weight" that is the 5-year project of NEDO (New Energy and Industrial Technology
Development Organization), has been engaged since Oct. 2003. In this project, massproduction and design technologies of CFRP automobile body made with continuous
fiber fabric has been developed. This paper shows frame works of this project and someresults.

INTRODUCTION
A strong demand for improving a fuel consumption of automobiles, which
eventually contributes to reduce CO2 emission and to prevent global warming, isexisted. In Europe, about 25% improvement of the fuel consumption until 2008 was set
to goal. Also in Japan, various approaches for improving the fuel consumption havebeen worked on actively.
One of the approaches is to reduce a weight of automobiles body. So far, automobile
materials have been replaced from steel to aluminum. Moreover, plastics with andwithout reinforcement are being considered as possible automobile materials amongautomobile manufacturers. In April 2002, at Council for Science and Technology
Policy, METI (Ministry of Economy, Trade and Industry) suggested the developmentof innovative materials, which is light and excellent in strength, to realize energy
conservative and safer next generation automobile, as the priority subject for anenhancement of international competitiveness. According to aluminum, a project ofaluminum alloy technologies development for automobile lightweight has already been
adopted as a government program in 2004 fiscal year.
On the other hand, CFRP (Carbon Fiber Reinforced Plastics), whose strength ishigher than high tensile steel, are currently in a center of attention as the mostlightweight effective materials. However it has been said to be difficult to produce

automobile parts made of CFRP in a mass production rate, which has been expected tobe solved as soon as possible.
In Europe, TECABS (Technologies for Carbon fiber reinforced modular
Automotive Structures) had been early started since April 2000 (ended in August 2004)
to reduce a weight of automobiles with use of low cost CFRP and improve energy
consumption and CO2 emission drastically. Automakers such as Volkswagen, Volvo,
Renault, material makers, parts manufacturers, software venders, and research institutes(Belgium, France, Germany, Switzerland and Sweden) took parts in that project.
Objectives in that project are to reduce a weight of BIW (Body-In-White) and a numberof parts. In 2004, trial CFRP floor pan was produced using RTM (Resin TransferMolding) method [1].
In such situation, a material, parts manufacturer (Toray) and an automaker (Nissan)
are directly cooperated and started "R&D of Carbon Fiber-Reinforced Composite
Materials to Reduce Automobile Weight" in Japan. This project is a 5-year government
program (NEDO) and has been engaged since October 2003.

GOALS OF THIS PROJECT
Objectives of this CFRP automobile body project is to design an automotive bodywhich exhibits 50% lighter and 1.5 times higher impact energy absorption capability inthe full wrap collision test compared with a current steel body as shown in Table 1.
Especially, structural parts take over 70% in weight of BIW and take a major role in
impact energy absorption. So structural parts are mainly focused on in this project. To
achieve these high targets, continuous fiber fabric reinforced thermosetting resin is
selected as the material of automotive body. Conventionally, it was assumed that
continuous fiber fabric has a difficulty in handling and is inappropriate for mass
production, although it is excellent in strength and stiffness. So 10-minute molding,which is appropriate for automobile parts production rate, 30,000 unit/year, has been
also set to the objectives of this project. There are many CFRP molding methods asshown in Figure 1. For example, Injection molding or SMC are appropriate for high rate
production, but those discontinuous fiber and cannot be expected to be high mechanicalproperties. In opposite side, prepreg and RTM use continuous fiber and can be expected
to be high mechanical properties, but they are inappropriate for high rate production.
Especially, RTM use dry fabric (no resin impregnated fabric) that is superior to prepreg
in drapability and easy to fit deep draw shape as automobile parts are often so.
Innovative technology, “Short cycle RTM” has been newly developed in this project tomake full use of that RTM characteristics and realize 10-minute molding cycle.
Figure 2 shows the schedule. As a preliminary of this project, Toray and Nissan had
made some studies to confirm concepts. NEDO recognized the results of theseresearches and formally signed on for this project in October 2003. In addition to Torayand Nissan, 5 universities, that is to say, Tokyo Institute of Technology, NihonUniversity, Kyoto Institute of Technology, University of Hyogo and University ofTokyo has been taken part in. As the milestones, 10-minute molding demonstration
applied to door panel was set until March 2006. Also, 10-minute molding
demonstration applied to platform and design of 50% lighter and 1.5 times safer CFRP
BIW with compared with steel one was set until March 2008.

Table.1 Objectives of this project.

Figure 1 Various molding method and objectives of this project.

Figure 2 Schedule and milestones of this project.

OVERVIEW OF RESULTS OF TECHNICAL SUBJECTSIn this project, there are 4 technical subjects that are corresponded to the each stagesof automobile life cycle as shown in Figure 3.
First one is “Short cycle integrated fabrication technology” this subject iscorresponded to “Fabrication” stage in the automobile life cycle. A technology thatrealizes a short cycle fabrication of CFRP automotive body made of continuous fiber
fabric reinforced composites is developed in this project.
Second one is “Metal/CFRP joint technology”, this subject is corresponded to“Assemblage” stage. A technology of adhesive joint between metal and CFRP having
almost equivalent strength to conventional welding joint between metals is developed.
Third one is “Safety design technology”, that is corresponded to “Use” stage. A
simulation technology for CFRP energy absorber is developed and that technology
assists CAE design for automotive body. In addition, a CFRP automotive body, that is
1.5 times larger in energy absorption than steel body, is designed.
Last one is “Recycle technology”, that is corresponded to “Scrap” stage.
Dismantlable adhesive is developed to separate easily metal and CFRP in scrapping. Inaddition, to apply recycled CFRP to automobile non-structural parts, a technology for
re-fabricating CFRP materials which can be recycled for additional two times, isdeveloped.
The current statuses of above-mentioned four subjects are summarized below andalso future works to realize CFRP automobiles are addressed.

Figure 3. Four technical subjects in this project.

Subject 1: Short cycle integrated fabrication technology
The goal of this project is to develop of an automobile primary structure parts,
platform can be fabricated for 30,000 unit/year. Fabrication quantity is decided by thetime from the molding tool open to molding tool close, what is called molding cycle
time because molding tool is generally very expensive. If 1 molding tool is used forproduction, it is necessary to realize 10-minute molding. RTM method is well-suited toautomobile parts that are often in complicated shape, short cycle RTM has beendeveloped as shown in Figure 1. Also preforming process, which continuous fiber
fabric is made to 3D preform, should be developed for shortening the process time to go
hand-in-hand with short cycle RTM [2].
In this paper, two innovative technologies to realize short cycle RTM are introduced
below. So-called, “Rapid cure resin” and “Rapid impregnation method” have beendeveloped in this project. As shown in Figure 4, conventional RTM had taken a longtime to achieve both appearance quality and mechanical property. For example, it had
taken 160 minutes to mold 2m2 panel parts with use of epoxy resin. 20% is the resin
injection time to impregnate resin into dry fabric and more than 50% is the resin curetime. These two steps took the large part of molding cycle time that should be shortened
drastically. The goals are 3 minutes resin injection and 5minutes resin cure. That means
the total time from resin injection to demolding is shortened 1/15, from 125 minutes to8minutes.
At first, “Rapid cure resin” has been developed. RTM is the molding method thatresin impregnates into dry fabric. Thus, resin flow time in low viscosity less than 300
cps to resin flow through the dry fabric easily need to be long. Conventional RTM resin
used to be amine cure epoxy resin because of high mechanical property. To achieve thelong resin flow time, resin cure time also becomes long as shown in Figure 5.
Breakthrough is an anionic polymerization with a chain transfer agent. This curemechanism enables 3 minutes low viscosity to flow through dry fabric easily and only
following 2 minutes cure rapidly at same temperature. The mechanical properties arealmost equivalent to that of the conventional RTM resin and its composites, whichindicates the rapid cure resin composites are appropriate for automobile structural parts[3].
Secondly, to utilize rapid cure resin fully, resin injection time should be shortenedless than 3 minutes. As shown in Figure 6, Conventional RTM injection method thatresin flows in face took long time because of fluid resistance of dry fabric, and so larger
scale of molded product took more time. Sometime resin flows along the edge part offabric where fluid resistance is very low. Thus, impregnation could not be controlled
and non-impregnation part could be often generated. That is one of the reason RTM
lacks in consistency. In addition, because in this project 3 minutes impregnation should
be applied to large-scale parts such as platform, completely different method had beenrequired. Breakthrough is multi gate injection. According to developed rapid
impregnation method, impregnation has been controlled though the fabric thickness at astretch and resin has not through the edge of fabric in early stage. Finally this method
achieved 2.5 minutes impregnation. Multi gate injection method seems to be worried
about weld. Generally, decline of mechanical properties at the region of weld is serious
on injection molding with thermoplastic, but in this case, thermosetting resin is applied
and the resin from different gate meets with having reactivity, weld does not occur.

These two innovative technologies have successfully allowed the 10 minutes
molding demonstration applied to door inner panel in February 2006. Figure 7 shows
the door inner panel fabricated by these technologies.

Figure 4. Time apportion of molding process.

Figure 5. Concept of cure index curve of rapid cure resin.

Figure 6. Schematic of injection methods.

Figure 7. Door inner panel demonstrated 10-minute molding.

Subject 2: Metal/CFRP joint technology
Joint technology is the key of BIW assemblage. In this project BIW are planed to be
fully made of CFRP, but especially at joint parts there are many metal inserts anddifferent materials meet. The combination of co-cure bonding [4], adhesive bonding
and mechanical joints need to be applied properly. On the one hand structural adhesive
database has been completed and on another hand various attachment parts have been
concretely developed one by one.
Structural adhesive database takes account of adherend types (steel, aluminum,CFRP) and has been taken under static, durability, fatigues and exposure condition. The
adhesives of which bond strength is more than 20MPa under automobile environment,
through out from –40°C to 80°C are screened out.
Also various attachment parts, especially which are often critical under automobile
use, are selected and concretely verified one by one because input loads and required
performances of any attachments are unique to each other. For example, sheet anchor
and sheet belt anchor attachments have been developed as shown in Figure 8. Theseattachments are very important for passenger safety in crash and also required specs aresevere. The attachment specification and shapes are analyzed by FEM and designed.
Actually in mechanical test, these attachments are superior to present attachment invarious direction loads.

Figure 8. Example of anchor attachment mechanical test.

Subject 3: Safety design technology
The prime objective is CFRP BIW design. Preliminary design of that was finishedin March 2006. To realize aggressive target, 50% lightweight and 1.5 times moreenergy absorption compared with steel body, accurate simulation technologies andenergy absorption structure technologies have been developed.
As accurate simulation technologies, CFRP dynamic analysis is very importantbecause passenger safety in crash is taken quite seriously in automobile design. CFRP
dynamic analysis in large scale such as full automobile body are insufficient knowledge,
and new types of CFRP parts such as crush tube are very difficult to stable analysis
though the crush tube takes important role in crash and needs to be accurate analysis.
Also as energy absorption structure technologies, energy absorbers in various
fracture modes are developed. The energy absorber, CFRP crush tube was permanently
attached to actual CFRP parts, front side member and proved its potentiality in head-on
collision test as shown in Figure 9. The CFRP crush tube gained more energy
absorption than the target, present steel one.

Figure 9. Verification of energy absorption in crash test.

Subject 4: Recycle technology
Cost and recycle matters had been always supposed to be weak point of CFRP
automobile use. two technologies in this project can be defied that common wisdom.
Recycle starts at the step of the separation between metal attachment and CFRP scrapsof automobile body. In the next step, standard recycled CFRP material is fabricatedwith use of CFRP scraps. That standard recycled CFRP material can be use in press andinjection to make automobile non-structural parts. In these two steps, separation andfabrication, new technologies have been developed.
In separation steps, an innovative technology, dismantlable adhesive has beendeveloped. The separation concept is as follows. Dismantlable adhesive includes thefillers that expand in high temperature. While the adhesive is heated, its matrix modulus
and strength is getting down and its fillers expanding force is going up. The adhesive
can be designed to separate matrix and fillers at certain temperature. This concept
achieves metal attachment and CFRP scraps separation in few minutes easily. Of course,
as a structural adhesive, its bonding strength should be more than 20MPa. Bothheat-resistance at 80°C and dismantlability more than 150°C not to dismantle in coatingprocess are also required. By applying expandable graphite to the filler, thedismantlable adhesive that mature these specs are developed and less than 5 minutesdismantlability has been demonstrated as shown in Figure 10.
In fabrication steps, recycled CFRP material can be endured Three times as
automobile parts. CFRP scraps are collected and crushed. That crushed CFRP andthermoplastic resin are compound at properly content ratio and pelletized to makerecycled CFRP material for standard use of injection or press. As shown in Figure 11,
carbon fiber are homogenously distributed in the material and that’s mechanicalproperties are enough to be applied to automobile non-structural parts. Also required
mechanical properties can be improved and controlled by crushed CFRP content ratio.

Figure 10. Demonstration of dismantlable adhesive.

Figure 11. Example of recycled CFRP examination.

RESULTS SUMMARY AND FUTURE WORKS
Two innovative technologies, “Rapid cure resin” and “Rapid impregnation method”
have been developed. Rapid cure resin achieved 3 minutes resin flow and total 5
minutes resin cure at same temperature. Rapid impregnation method achieved 2.5
minutes impregnation into dry fabric. These technologies have enabled short cycle
RTM, only 10-minute molding and demonstration succeeded with applied to door inner
panel in February 2006. Scale-up study of 10-minute molding is now going on and will
demonstration with applied to platform until March 2008. Also automation system ofpreform process with use of continuous fiber fabric is currently under development.
Screening of adhesives of which bond strength is more than 20MPa through out
from –40°C to 80°C and joint technologies suitable for automobile body structure havebeen almost developed. Now automation of bonding process design is carried forward.
Preliminary design of BIW was finished. Head-on collision test with CFRP front
body is planed in 2006 and its results will be returned on next design of BIW.
An innovative adhesive that can dismantle adherends has been newly developed and5 minutes dismantlability was demonstrated. Also recycled CFRP materials have been
examined for applying to automobile non-structural parts and realize closed recycle.
This recycled CFRP materials will be demonstrated to endure three times use asautomobile parts.

ACKNOWLEDGEMENTS
This R&D has been conducted as the part of “New Global Warming Prevention
Technology Program” supported by NEDO. The authors would like to thank Nissan
Motor Co., Ltd., universities partners for their technical contributions.

REFERENCES
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The 9th Japan International SAMPE symposium, pp. 68-73.
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