Automobile "marriage" long glass fiber reinforced polypropylene plastic

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The research and application of long glass fiber reinforced polypropylene materials on automotive parts is one of the hotspots in recent years. This paper briefly describes the characteristics of long and short glass fiber reinforced polypropylene materials, and analyzes the application of long glass fiber plastics in typical components such as front end modules, instrument panel skeletons, and door modules.

Long glass fiber reinforced polypropylene plastic refers to a modified polypropylene composite material with a glass fiber length of 10 to 25 mm. The three-dimensional structure is formed by injection molding, and the English is Long Glass Fiber polypropylene, abbreviated as LGFPP. There are also many materials at home and abroad that refer to long-fiber reinforced thermoplastics as LFT, the abbreviation of Long-fiber reinforce. From the material definition, LGFPP belongs to the LFT.

Material characteristics

Microstructure determines macroscopic properties, so 10~25mm long glass fiber reinforced plastic (abbreviated LGFPP) has higher strength, stiffness, toughness, dimensional stability and warp than ordinary 4~7mm short glass reinforced plastic (abbreviated GFPP). Low curvature and other advantages. In addition, long glass fiber reinforced polypropylene materials do not produce significant creep even when subjected to high temperatures of 100 ° C, and have better creep resistance than short glass fiber reinforced polypropylene.

On the injection molded product, the long glass fiber is staggered to form a body network structure. Even after the polypropylene substrate is burned, the long glass fiber network still forms a glass fiber skeleton of a certain strength, and the short glass fiber generally becomes a fiber without strength after burning. skeleton. This situation is mainly caused by the aspect ratio of the reinforcing fibers determining the reinforcing effect, the critical long diameter = L / D, the critical length to diameter ratio of less than 100 filler and short glass fiber without reinforcement, and the critical length to diameter ratio is less than 100 Glass fiber plays a reinforcing role.

Compared to metallic materials and thermoset composites, long glass fiber plastics have low density and can reduce the weight of the same parts by 20~50%; long glass fiber plastics can provide designers with greater design flexibility, such as parts with complex shapes. The number of integrated parts is used to save mold cost (the cost of long glass fiber plastic injection mold is about 20% of the cost of metal stamping mold), reducing energy consumption (the production energy consumption of long glass fiber plastic is only 60~ of steel products) 80%, 35~50% of aluminum products), simplifying the assembly process.

What are the typical automotive application parts?

Based on the application advantages of long glass fiber materials, it has become more and more widely used in automotive applications. On the mainstream models and new models, we have increasingly seen the following components using long glass fiber reinforced polypropylene materials, long fiber reinforced polypropylene. It is used for the dashboard body skeleton of the car, the battery bracket, the front end module, the control box, the seat support frame, the spare placenta, the fender, the chassis cover, the noise partition, the rear door frame, and the like.

Below, we will introduce several typical application components of long glass fiber plastic.

Front-end module: For the front-end module of the car, PP-LGF30 material can be used to integrate more than 10 traditional metal parts such as radiator, horn, condenser and bracket into one whole; it is more corrosion-resistant, less dense and weight than metal parts. Reduced by about 30%, with higher design freedom, can be directly recycled without classification processing; reduce manufacturing costs, and have obvious cost reduction advantages.

The plasticization of front-end modules of foreign brands such as Volkswagen and Ford has been successfully applied for many years. In recent years, independent brand car companies have gradually begun to conduct autonomous design and new material application research. For example, the FCV-863 project led by SAIC has plasticized the front-end module and reduced the weight by 3.03kg. Changan Automobile, at the 2011 Auto Show, demonstrated the CX30 compact sedan with all-plastic front-end modules, and assembled 22 metal parts into one injection molded part, greatly simplifying the front end structure of the CX30 model and making the part weight-reducing. Up to 40% and reduce the total weight of the car by about 4kg. Changan Yidong 2015 plastic front-end module original steel parts 10.13kg, plastic parts 6kg, expected to lose weight 4.13kg, weight loss rate of 41%; and will be applied to C201, C206, C2X and other production models. Great Wall Motor's latest car, which was mass-produced in June 2014, has adopted a plastic front-end module that weighs 30% to 4.7kg. Jianghuai Automobile is also promoting plastic front-end modules and other products on production vehicles. In 2011, Chery Automobile undertook the “Technology Support Program for the development of fiber-reinforced plastic front-end modules and its integration on target vehicles”, systematically developing plastic front-end modules and successfully applying them to production models (such as Arrizo 7). )on.

In terms of plasticizing the front-end module of the truck, SABIC and SCANIA successfully developed the truck front-end frame and formed a modular supply, reducing the weight from 5.15kg to 3.29kg and reducing the weight by 33%.

Dashboard body skeleton: For soft instrument panel skeleton materials, LGFPP is more powerful than filled PP material, the flexural modulus is changed, and the fluidity is better. Under the same strength, the thickness of the instrument panel design can be reduced to reduce weight. The weight loss effect is about 20%. At the same time, traditional multiple component dashboard bays can be developed as a single module. In addition, the front defrosting air duct body of the instrument panel and the middle skeleton of the instrument panel are generally selected from the same material as the skeleton of the instrument panel body, which can further enhance the weight reduction effect.

2011, Ford Maverick and Ford Kuga dashboards (made with Trexel MuCell microcellular foam injection molding technology and SABIC's PP-LGF20), this application will reduce each vehicle compared to conventional injection molded polypropylene panels. With 0.45kg, the production time is reduced by 15% and the cost is reduced by $3. At present, most of the high-end soft instrument panel skeletons such as BMW and Audi are made of long glass fiber plastic as the dashboard material. For example, in 2010, BMW's 7-series car dashboard skeleton was made of long glass fiber plastic, and the instrument panel finished product could be 20% lighter than conventional materials. At the same time, long glass fiber polypropylene materials are compatible with BMW's automated integral foam injection molding technology; higher strength and stiffness can be achieved with fewer raw materials, and the instrument panel can be better. At present, BMW 3/5/7 series, Mercedes-Benz E and other high-end car dashboard skeletons use LGFPP materials.

Among the joint-venture brand car companies, the dashboard skeletons of various production vehicles such as FAW-Volkswagen, Shanghai Volkswagen, and Changan Ford have adopted LGFPP. In the independent brand, the Great Wall high-end SUV instrument panel skeleton PP-LGF20 replaced the modified PP from 3mm to 2.2mm, and successfully mass-produced. The dashboard of the mid-level and above passenger vehicles such as BYD Tengshi and SAIC Roewe 550 are also gradually adopting LGFPP materials.

Door module (door middle panel skeleton)

The modern Sonata plastic door module that used SABIC STAMAX long glass fiber polypropylene won the American Plastics Engineers Association (SPE) Innovation Award. The front door module of the new Ford Fiesta models integrates a variety of functional components such as door locks, door lifts, speakers, anti-theft devices and more. Mazda 6 door inner panel, FAW Pentium B70, etc. are all made with LGFPP.

Shift mechanism: The shifting mechanism mainly uses metal material and short-fiber nylon material. At present, the gear shifting mechanism of a few foreign models has tried to replace the short glass fiber nylon material with long glass fiber reinforced polypropylene material. Nylon materials are easy to absorb water, and the water absorption of finished parts is generally above 0.7%. In the high temperature and high humidity environment, there is a risk of failure; if it is changed to a long glass fiber polypropylene material that is not easy to absorb water, such problems can be avoided. At the same time, the use of long glass fiber reinforced PP material can play a role in reducing weight and reducing costs.

Electronic accelerator pedal: The electronic accelerator pedal arm needs to bear a large force. Therefore, its material needs to have excellent mechanical properties and good toughness. The material properties cannot be greatly changed at high and low temperatures. At present, the electronic accelerator pedal arm is mainly made of glass fiber reinforced PA material. Ticona material manufacturers have successfully used long glass fiber plastic (Celstran PP-LGF40/50) for electronic accelerator pedals, as shown in Figure 9, with low odor and high strength, better than PA materials. low cost.

Long glass fiber plastic can be used in the seat back, which can replace the traditional steel frame to achieve weight loss of 20%, excellent design freedom and mechanical performance, and expanded seating space.

In addition, long glass fiber plastic can be made into battery tray, sunroof frame, spare tire compartment and spare tire cover. Ford KUGA (2010) uses the back door inner panel made of PP-LGF40.

Difficulties and focus of material development

The reduction of weight loss has always been a topic of concern for the whole vehicle. Compared with the successful application of PP-LGF as a lightweight new material by foreign automakers, there are still many difficulties in the implementation of independent brands. such as:

(1) EVI (abbreviation of Early Vendor Involvement) concept: the supplier of material supplier system parts, involved in the new model project during the concept development stage, fully understand the demand for materials of the host factory users, thereby improving the performance of the products and Service; if only the benchmark car materials are used as the basis for material selection, there is a gap of about 5 years in the listing of the model and the benchmark car.

(2) Cost analysis: If the price of raw materials per kilogram is higher than that of metal materials, the cost of plastics in the early stage is less than 50% of the steel molds of the parts. The molds are only the same parts. Steel molds 30~40%; integrated peripheral components, modular supply, can further save the cost of assembly and assembly, reduce assembly tools and save space.

(3) Other aspects: the change of the material type of the component, the change of the material shrinkage rate requires the development of a new mold; at the same time, for the special material of the long glass fiber, it is necessary to use a processing equipment different from the conventional injection molding machine. Although most of the technical breakthroughs as purchased parts are undertaken by the first-tier suppliers, the main equipment factory needs to deal with various technical problems in the process of industrialization of long glass fiber materials.

In the application and development of long glass fiber reinforced plastics, foreign auto companies are more in-depth and advanced in application development, and domestic independent brands are more absorbing the mature application cases and advanced technologies of foreign-funded vehicles.

Among the self-owned brands, Great Wall Motor and SAIC passenger cars are at the forefront, and Geely, Chery and Changan passenger cars have also carried out a large number of application development work. Great Wall Motor has carried out research work on plastic parts products, and some of them have been mass-produced. With the support of national projects, SAIC has studied and used many LGFPP parts on models such as pure electric vehicles E50. In the industry, relying on the automotive lightweight alliance, the exchange and communication of lightweight technology (including lightweight materials technology); in the company, build a vehicle lightweight technology application platform, timely introduction of new materials, new technologies and new processes To the vehicle development.

In terms of material substitution, long glass fiber plastic products can simultaneously reduce weight and reduce costs. In the past, short glass fiber nylon materials were used instead of metal materials. In recent years, with the development of lightweight materials, long glass fiber reinforced polypropylene materials have gradually replaced short glass fiber nylon plastics on more and more automobile parts. Research and application of LGFPP materials in automobiles.

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