Fiber reinforced thermoplastic composites

Fiber Reinforced thermoplastic composite is an important component of composite materials. It uses glass fiber (GF), carbon fiber (CF), arfiber fiber (AF) and other fiber materials to strengthen various thermoplastic resins, which is called FRTP (Fiber Reinforced ThermoPlastics) abroad. Advanced fiber reinforced thermoplastic composites have become a research hotspot in the material industry because of their excellent properties such as high toughness corrosion resistance and fatigue resistance, simple molding process and short cycle, high material utilization rate (no waste) and no need for low temperature storage.

Typical performance benefits of FRTPS

Thermoplastic composite FRTP has been used for decades. Compared with phenolic resin, urea-formaldehyde resin, epoxy resin, polyurethane and other thermosetting composites, thermoplastic composite has some special properties:

◆ Low density, high strength: the density of FRTP is 1.1-1.6g/cm3, only 1/5-1/7 of steel, lighter than thermosetting FRP 1/3-1/4, can obtain higher mechanical strength and application grade with smaller unit mass.

◆ Large degree of freedom of performance designability: The physical, chemical and mechanical properties of FRTP are designed through reasonable selection of raw material types, proportions, processing methods, fiber content and layering methods. As there are many more types of matrix materials than thermosetting composites, The most important include polyether ketone (PEKK), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), nylon (PA), polyether imide (PEI), etc., therefore, its material design freedom is much larger.

◆ Thermal performance: general plastic use temperature of 50-100℃, with glass fiber reinforced, can be increased to more than 100℃. The thermal deformation temperature of PA6 is 65℃, and the thermal deformation temperature can be increased to 190℃ after 30% glass fiber reinforcement. The heat resistance of PEEK reaches 220℃. After reinforced with 30% glass fiber, the service temperature can be increased to 310℃. Thermosetting composite materials cannot reach such high heat resistance.

◆ Chemical corrosion resistance: mainly determined by the performance of the matrix material, there are many kinds of thermoplastic resin, each resin has its own anticorrosion characteristics, therefore, according to the use of composite materials environment and medium conditions, the matrix resin is optimized, generally can meet the use requirements. FRTP also has better water resistance than thermosetting composites.

◆ Electrical performance: FRTP generally has good dielectric properties, does not reflect radio waves, through microwave performance is good. Because the water absorption rate of FRTP is smaller than that of thermosetting FRP, its electrical properties are superior to the latter. Adding conductive materials to FRTP can improve its conductivity and prevent static electricity.

◆ Waste can be recycled: FRTP can be reprocessed and formed, waste and corners can be recycled, and the physical and mechanical properties do not change significantly, will not cause environmental pollution, well adapt to the environmental protection requirements of the material industry in today's world.

Classification of FRTP

There are so many different types of FRTPS, and the industry is so full of acronyms for terms that it can be confusing. According to the fiber retention size (L) in the products can be divided into: short fiber reinforced thermoplastic (SFRT, L < 1.0mm), long fiber reinforced thermoplastic (LFT or LFRT, generally L > 10 mm), continuous fiber reinforced thermoplastic composite plastic (CFRT, general fiber continuous not cut).

Compared with SFRTS, LFT has low density, high specific strength, high specific modulus, and strong impact resistance, and is suitable for harsh application conditions. This is one of the main reasons why LFT is favored by downstream applications. The widely used LFT materials can be roughly summarized into three categories: GMT (Glass Mat Reinforced Thermoplastics), and LFT-G (Long-Fiber Reinforced Thermoplastic) pellets Granules) and Long-Fiber Reinforced Thermoplastic Direct are formed in line LFT-D (Long-fiber Reinforced Thermoplastic Direct).

CFRTS are recyclable, with high specific strength and stiffness, good corrosion resistance, impact resistance, heat resistance, low cost and design flexibility. They have great application potential in automotive lightweight design, and can replace some metal materials and high-end polymer materials.

Application of FRTP

With the appearance of aromatic thermoplastic resin matrix (such as PEEK, PPS) with excellent rigidity, heat resistance and medium resistance, as well as the development of high strength, high modulus, high temperature resistance, corrosion resistance and other high performance fibers such as carbon fiber, aramid fiber, silicon carbide fiber, advanced FRTP has been applied in more and more industrial fields, such as: Rail transit, automobile, aerospace, household appliances, electric power and other industries.

aerospace

FRTP's high stiffness, low processing cost and reprocessing capability, excellent flame retardant, low smoke and non-toxic properties, and its curing cycle can be measured in minutes make it an ideal material for lightweight, low-cost aviation structures.

In aircraft airframe structural components, FRTP is mainly applied to floor, leading edge, control surface and tail parts, which are relatively simple appearance of secondary load bearing components. Airbus A380 aircraft, Airbus A350 aircraft, Gulfstream G650 business jet and AgustaWestland AW169 helicopter are the most popular applications of thermoplastic body parts. The most important FRTP structural component on the Airbus A380 is the fiberglass /PPS wing fixed leading edge. The FRTP of the Airbus A350 airframe is mainly distributed in the movable wing spars and ribs and fuselage connections. The Gulfstream G650 marks a milestone in FRTP applications by using carbon fiber /PEI for the pressure diaphragm ribs and carbon fiber /PPS for both the rudder and elevator

◆ Automobile

The development of low cost, short cycle and high quality composite technology has become one of the key factors to promote automotive lightweight. Many domestic auto companies have already cooperated with injection molding equipment enterprises with advanced composite technology. Applications in passenger cars are: seat and its skeleton, window guide, door panel, bumper bracket, hood, front end bracket, foot pedals, dashboard skeleton, deflector, car bottom plate, spare tire box, battery carrier, automotive intake manifold. In domestic automobile models such as Passat, POLO, Pola, Audi A6, Golf, Buick Excelle, Buick GL8 commercial vehicle, etc., a large number of high-performance FRTP parts have been adopted, most of which use GMT or LFT

The application of PP honeycomb composite plate in box truck is mainly to replace the steel frame of aluminum alloy corrugated plate and steel corrugated plate in box truck.

◆ Rail transit

According to the bearing characteristics, it can be roughly divided into two categories: composite main bearing parts and composite non-main bearing parts. The main load-bearing parts of composite materials mainly refer to the large load-bearing components of train body, cab and bogie frame. It is the key for composite materials to replace traditional materials and realize vehicle lightweight. The non-main load bearing parts of composite materials can be divided into non-main load bearing parts (such as body, floor, seat and other non-main load bearing parts) and auxiliary parts (auxiliary components such as bathroom, toilet and water tank).

Market status and prospect

Compared with thermosetting composites, FRTPS tend to have higher initial costs, higher processing temperatures, and often higher tooling costs. Traditional parts manufacturers may not be familiar with modern FRTP processing techniques, and their limitations are often magnified and perceived as less than thermosetting composites. The advantages and utilization value of FRTP have not been fully recognized and developed, which directly affects the normal growth of market demand and hinders the further development and application of FRTP from the source of supply and demand. Secondly, the high requirements of FRTP manufacturing technology restrict the entry of some enterprises with insufficient technical level and production capacity to a certain extent. Moreover, the cost of raw materials is high, and the price of high-end thermoplastic resin is tens of times that of ordinary thermosetting epoxy resin. In addition, the production technology requirements are high, and all kinds of factors superposition, resulting in the price of FRTP, especially the composite products using high-end thermoplastic resin as matrix, such as PEEK and PI, is daunting, and the downstream application demand is restrained.

Nevertheless, once the technical quality reaches the requirements, when the price cost is reduced to the acceptable range of the market, when the scientific research results are well transformed into productivity, with the rapid development of aviation manufacturing, automobile, electronic and electrical, wind energy, high-end medical equipment, intelligent machinery and other industries, our FRTP industry will certainly usher in a new development stage, In the next few years to harvest more market opportunities and share space, the prospect is still worth looking forward to.