In recent years, with the rapid development of the automobile industry, people's various requirements for car seats continue to improve, car seat lightweight, multi-functional, environmental protection, comfort and safety are people's basic needs for car seats, therefore, these aspects have gradually become the main direction of the development of car seats. Long fiber composite material is composed of resin and long fiber composite material, with a variety of characteristics, such as high strength, low density, short production time and easy to form, suitable for the current development trend of car seats, so in the automobile industry, it has gradually become the first choice of car seat materials.

1. Overview of car seats

Car seats are mainly composed of four parts: seat cover, seat pillow, seat foam and seat skeleton. In addition, due to different market demands, some seats also have armrests, waist brackets or massage and other related comfort components, and some seats have cuphorers, drawers and other storage functions.
At present, the lightness, comfort and safety of car seat design are of great significance. However, most of the main materials of conventional seats are metal materials, which have high density and heavy weight. Therefore, the development space of improving the lightweight of car seats only by optimizing the structure and design is limited. Long fiber reinforced composite materials have excellent mechanical properties and can achieve significant lightweight effect. Therefore, they are gradually applied in the automotive field, not only in most simple non-important parts, but also in some complex shape functional parts, such as the seat frame and the front segment module.

2. The importance of automobile lightweight

Automobile lightweight means that on the basis of the safety performance and strength of the automobile can be guaranteed, the overall weight of the automobile can be reduced to the maximum extent, so as to enhance the power of the automobile, and reduce emissions and fuel consumption. According to the relevant tests, the fuel quantity of the vehicle has the most direct relationship with the weight of the vehicle quilt itself. The fuel consumption of 100 kilometers can be reduced by 0. 2 and 0. 8 L for every 1 kg weight reduction of the vehicle, which is usually about 4. 5% of the original consumption. Therefore, under the background of environmental protection and energy saving in automobile development, the lightweight of automobile is of great significance in the design and manufacturing process of modern automobile.
Car seat is one of the most important interior parts in automobile. According to the survey, the weight of the car seat in the entire body accounts for 15% of the proportion. Although the car seat occupies a small proportion in the total weight of the body, however, as one of the large and extremely important parts of the car interior, its contribution to the lightweight process of the whole car can not be underestimated. Car seat is one of the more complicated parts in the whole process of car design. The design process of the car seat must be considered from many aspects, such as safety, the beauty of the shape, functional diversity and comfort, must be established in line with the requirements of the traditional car seat under the premise, can implement the lightweight design of the car seat, reduce the weight of the car seat at the same time, the basic performance of the car seat must be guaranteed, especially the safety of the seat. Under the influence of these requirements, the lightweight design of car seat becomes more challenging and more worthy of people's research.

3. Application status of long fiber composites in automotive field

With the rapid development of industrial economy, long fiber composite materials have also been developing rapidly. At present, long fiber composite materials have become one of the fastest growing industries in the reinforced plastics industry. In Europe and the United States and other developed countries, long fiber composite materials have been greatly developed, such as the Japanese Emperor Company, LNP Company, Ticona company, Saint-Gobain Company and other internationally well-known material enterprises have developed long fiber composite materials.
The application proportion of home automobile field is large, accounting for about 33% of the total consumption, and will continue to grow with the development of the automobile industry. At present, long fiber composite materials are widely used in automotive interior, functional parts and structural parts. Replacing traditional metal materials with long fiber composite materials can not only reduce the weight of automobiles, but also simplify the production process and modular production. General Motors, one of the world's biggest carmakers, has already applied fiberglass composites to the cargo boards of sport vehicles and pick-up trucks. Ford is one of the leaders in the use of composite materials, producing cars that use fiber-reinforced sheet plastic as body insulation. In 2011, PP-LGF50 material was used in the driver's seat of a certain type of car produced by BMW, which reduced the weight of the car seat by 63% and also increased the service life of the car seat.

4. Application of long fiber composite material in car seat

4.1 Improve the service life and safety of the seat
The fatigue resistance of long fiber composites is relatively high. It has more matrix, and its fatigue fracture will not break out suddenly, but slowly expand from matrix to collective interface and fiber. Therefore, people can find the damage of long fiber composite materials in advance, and take corresponding remedial measures in time, effectively improve the service life of the seat. In addition to fatigue resistance, long fiber composite materials also have stable safety. If overloaded components are made of this material, the role of the car seat will not disappear immediately, but a small number of fibers will be broken first, and the load will be quickly redistributed and transferred to the fibers that are not damaged, so that the whole component will not be broken by heavy objects in a short time.

4.2 Reduce the vibration amplitude of the seat
There is a large damping between the interface of the long fiber composite and the matrix, and it has a good vibration damping performance. When the long fiber composite with the same size and shape is subjected to the vibration test under the same conditions, the decay time of the former is shorter than that of the latter. Therefore, the vibration frequency and duration of the seat are reduced effectively by using the long fiber composite material.

4.3 Reduce seat cost
In the processing of long fiber composites, no chemical reaction is required, and the reinforced fiber is directly extruded in a predetermined direction and arranged at the same time
On the matrix, the layered structure is formed and pressed on the high speed hydraulic press, so that the long fiber composite can be processed. This method not only saves the cost of buying semi-finished products and reduces the manufacturing cost, but also guarantees the fiber length and optimizes the mechanical properties of the component [3]. In addition, long fiber composite parts can be made by combining the matrix with the fiber and then using the mold for heating and curing. In this process, the matrix changes from fluid to solid, so the car seat made of long fiber composite material is not easy to generate cracks.

4.4 Reduce the damage degree of the seat at high temperature
Long fiber material can achieve the effect of high temperature resistance in general conditions, ordinary aluminum alloy in 4 ℃, its elastic modulus will be greatly reduced, but under the same conditions, the use of long fiber material after the reinforcement of aluminum alloy, its elastic modulus and strength can remain unchanged. Because of the low thermal conductivity of long fiber composite, its high temperature resistance is better. The application of long fiber composite material to car seat can effectively reduce the damage degree of car seat under high temperature condition.

4.5 Maintain the stability of various performance of the seat
장섬유 복합재료의 많은 특성 중에서 높은 비강성과 높은 비강도가 더 중요하며 그 특성은 다양한 범위를 가지고 있습니다. 다른 섬유 재료, 섬유 함량 및 퍼짐 방향에 따라 설계된 제품 강도 지수, 난연성 및 탄성 계수도 다릅니다. 장섬유 복합재료를 한 방향으로 연신하면 연신 방향에 수직으로 재료를 연신할 수 있다. 이 성질은 일반적인 물질과는 완전히 다릅니다. 카시트의 설계 과정에서 설계가 용이하고 안정적인 성능을 유지할 수 있는 소재를 선택해야 합니다. 장섬유 복합 재료는 모든 측면에서 안정적인 성능을 유지하면서 다양한 형상을 유연하게 설계할 수 있습니다.

5. 결론

카시트는 자동차 부품의 지지력으로서 교통사고 시 차량의 안전을 보장하는 것이 매우 중요한 역할을 하기 때문에 가볍고 편안한 안전 및 기타 측면의 카시트 개발은 피할 수 없는 추세입니다. 장섬유 복합재료는 다양하고 우수한 성능을 가지고 있으며, 카시트의 품질을 향상시키면서 품질을 낮추고 성능을 향상시키는 동시에 원가를 낮추어 자동차 산업의 급속한 발전과 장섬유의 발전에 따라 복합 재료 기술 수준이 지속적으로 개선되고 자동차 시트에서 장 섬유 복합 재료 응용 전망이 점점 더 넓어 질 것입니다.