Composite Prepregs – Manufacturing, Benefits and Applications

Topics Covered

What is a Prepreg?
How are Prepregs Manufactured?
     Hot Melt Process
     Solvent Dip Process
Companies Involved in Prepreg Manufacturing
     Hexcel
     TenCate Advanced Composites
     Prepreg-ACM CJSC
     SGL Group
     Axiom Materials
Benefits of Prepregs
Applications of Prepregs
References

What is a Prepreg?

Prepregs are composite materials in which a reinforcement fiber is pre-impregnated with a thermoplastic or thermoset resin matrix in a certain ratio. Prepregs have unique properties as they are cured under high temperatures and pressures.

Generally, the resin matrix in prepregs is partially cured for ease of handling and is stored in a cool place to prevent complete polymerization. This B- stage prepreg will need to be heated in an autoclave or oven during manufacture of composite materials to achieve full polymerization. The reinforcement in a prepreg can be unidirectional fibers or a fabric.

How are Prepregs Manufactured?

Prepregs are produced using two main processes: hot melt process and solvent dip process.

Hot Melt Process

Both fabric and unidirectional prepregs can be produced using the hot melt process. There are two stages in this process. The first stage involves coating a thin film of the heated resin on a paper substrate. The reinforcement material and the resin are allowed to interact in the prepreg machine. On application of pressure and heat, the resin is impregnated into the fibre resulting in the final prepreg, which is ultimately wound on a core.

Solvent Dip Process

Only fabric prepregs can be produced using the solvent dip process, which involves dissolving the resin in a solvent bath and dipping the reinforcing fabric in the resin solution. Using a drying oven, the solvent is then evaporated off the prepreg.

Companies Involved in Prepreg Manufacturing

Some major companies that are involved in prepreg manufacture are listed below along with a brief introduction to their products.

Hexcel

Hexcel offers HexPly® prepregs for industrial applications. HexPly® prepregs use phenolic, epoxy, and BMI resin matrices. They are normally reinforced with unidirectional and multiaxial, glass and carbon fibers. Hexcel’s prepregs can meet a range of performance requirements such as good fatigue performance, low temperature cure, fire/smoke/toxicity performance and temperature resistance.

TenCate Advanced Composites

TenCate Advanced Composites is a US-based producer of “out-of-autoclave” composites, which are widely used in the aerospace industry by leading companies such as Lockheed Martin, General Atomics, Gulfstream, and Cirrus Aircraft. Both the wing structure and fuselage of Cirrus’s SR-22 aircraft is incorporated with out-of-autoclave composites from TenCate.

The company also manufactures vacuum cure only (VCO) prepregs, including cyanate ester, BMIs, and epoxy, for use at high temperatures. Its TC275 is an epoxy prepreg for low cure pressure part manufacture. It is ideal for fabricating thick parts as it provides low porosity and can also be used in aerospace environments. Another landmark product of the company is the TC350-1, which is a matrix for use in structural applications. It features good toughness and hot/wet performance.

Prepreg-ACM CJSC

Moscow-based Prepreg-ACM CJSC produces prepregs for polymer composites having high-quality mineral and carbon fibers in nano-filled epoxy and polyimide resins. These prepregs find use in many sectors including aircraft, construction, and wind power. Prepreg-ACM’s production process is ISO 9001 certified.

SGL Group

SGL Group is a global leader in carbon-based products. It has sophisticated prepreg manufacturing facilities across various locations. Its key products are the carbon fiber-based SIGRAFIL® unidirectional prepregs and the SIGRATEX® fabric prepregs made up of carbon fiber fabrics.

Axiom Materials

Axiom Materials is a major global producer of composite materials offering high-quality prepregs and other composite products. It manufactures a wide range of prepregs such as solution-coated prepregs, hot melt prepregs, woven fiberglass prepregs, woven aramid prepregs, woven carbon prepregs, and unidirectional prepregs.

Benefits of Prepregs

The major advantages of using prepregs are listed below:

  • Ease of use
  • Low void content
  • Good fatigue resistance
  • Control of laminate thickness
  • Good environmental and corrosion resistance
  • Control of fibre volume fraction
  • Clean process
  • Better conformity and quality
  • High specific modulus and strength
  • Very low thermal expansion coefficient
  • Enhanced vibration damping characteristics

Applications of Prepregs

Prepregs are being increasingly used in high performance applications in the composites industry and also in other sectors. Some key areas where prepregs currently find use are listed below:

  • Aircraft interiors, aerospace components, aircraft flooring, cargo liners
  • Automotive parts and components, tooling, ballistic panels
  • A/C ducting, electronic-transmission applications
  • UV resistant parts, sporting goods, high temperature parts
  • Honeycomb and foam panels, flame retardant laminates,
  • Carbon-carbon composites, high-rise flooring, high impact surfaces,
  • UAVs, seatbacks, doublers

The discovery of novel material formats have gone a long way in de-mystifying prepregs, speeding up their acceptance and decreasing their costs. As environmental concerns promote interest in new processes that replace wet lay-up, one ideal alternative can be low temperature prepreg.

References


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