Northern CompositesComposite materialsTowpreg

Towpreg

Towpregs are pre-impregnated reinforcement fibers wound on spools and then further processed.

The advantages such are:

Faster winding speed
More consistent part resin content
Access to carbon fiber choices in small quantities
Elimination of “Dry Fly” carbon fibers in working environment
Much cleaner process than wet winding

Filament winding is a composite manufacturing process which involves applying filament tows such as fiber glass or carbon fiber onto a mandrel. The filament layers are cross plied to achieve the strength characteristics determined by the part designer. The applied tows can be combined with a resin matrix immediately prior to application to the mandrel (wet winding) or the tows can be a towpreg which is a fiber/resin combination made by a vendor.

Wet winding is commonly used to make a wide range of products such as pipe, transmission poles, gas pressure bottles, liquid pressure vessels, etc. Generally, these applications do not require heat curing and the range of resin content of the part is wide. Usually, external pressure is not applied during cure. The process is mature and widely accepted. However, it can be messy, and employees are exposed to fumes of catalyzed resin and, dry fiber “fly”, and solvents.

Towpreg winding is used to make parts which require a narrow resin content range. The resin/fiber tows are generally processed at higher speeds compared to wet winding. The resulting fiber volume of the wound parts can be higher and more precisely controlled. The cost per pound of material is higher than wet winding. However, the cost of applied material is improved by more precise tow placement at higher speed. Also, clean-up of towpreg winding is minimal. Towpreg winding usually employs carbon fiber tows and resins with heat resistance properties. Also, part design is likely weight critical.

Mitsubishi manufactures a range of carbon fibers which are incorporated in FTM Towpreg products for a variety of applications. 3K, 12K and 24K tow sizes are available.

HMT301	General Purpose, toughened towpreg, controlled flow with versatile processing.
HMT316	Flame retardant, toughened towpreg designed for electrical applications
HMT317	General purpose towpreg.
HMT321	High temperature resistance, toughened
HMT321FR	High Tg towpreg with flame retardency.
HMT4030	Flame retardant meets FAR25.853
HMT507	Towpreg designed for pressure vessels. Cures at 205°F, in polyethylene’s limits
HMT5300	Low temperature variable cure towpreg with long out-time.
HMT6600	Highly toughened, high temperature cure towpreg. 350°F Cure, high temperature resistance