UV Curing for Filament Winding Composite Parts

Ultraviolet (UV) curing is used commercially for a variety of filament wound products made from composite materials including oxygen and liquid propane cylinders, baseball bats and PVC piping.

UV Curing for Filament Winding Composite Parts

The filament winding process lends itself quite naturally to UV curing, since parts rotate on a mandrel and can be easily exposed to UV light. And since UV curing happens in only a few seconds, it fits easily into the high production filament winding operation.

UV curing is applied to filament winding processes in several ways:

  • B-stage cure
  • Complete cure
  • Gel coat cure

B-stage curing

UV lamps can be placed after the resin bath, just prior to winding onto the mandrel to B-stage cure the resin onto the roving. The B-stage cure is not a complete cure, but partially cures the resin to a tacky stage. In addition to reducing the total cure time, there are several other benefits using this process, including:

  • The ability to wind at high approach angles because the roving is tacky
  • Faster winding speeds because resin clings better to the mandrel during winding
  • More consistent part throughout the wall thickness because resin is no longer forced out of the rovings closest to the mandrel as the part is wound
  • Less waste because the resin gels quickly so there is less dripping during winding and curing

Read how  Advanced Composite Products and Technology uses UV for B-stage curing .

Complete curing

Typically, the UV lamps can be located above and/or below the rovings (either glass, aramid or carbon) immediately after the resin bath. The lamps must cover the full width of the fibers. If the part is fabricated using fiberglass rovings, complete UV cure is usually possible. Another option is to place the UV lamps such that the UV light strikes the rovings immediately following winding onto the mandrel so the part can be cured as it is wound. If UV B-stage curing is used as described previously, then final UV cure can take place following winding of the part.

Gel coat curing

UV curable topcoat or gel coat is an ideal way to give filament wound parts a scratch-resistant, durable topcoat in a consistent, high production process. UV curing gel coats is popular with fabricators of filament-wound cylinders, golf shafts, etc. that require a smooth, attractive appearance. Typically, the topcoat is sprayed or manually brushed onto the fully cured part. Then the part rotates on a mandrel in front of the UV lamp.

Read about a filament winding machine builder who offers a  UV gel coat curing station.

Additional benefits of UV curing for filament winding

Several other benefits of using UV curing for filament winding include:

  • Reduced work-in-process, since the winding and cure time is shortened
  • Increased capital utilization, especially important for large parts, since the mandrels are freed up more quickly, resulting in more parts per mandrel
  • Improved worker environment because the operation is less messy and greatly reduces styrene smell

Filament winding machines are available with UV curing lamps. More often, however, UV lamps are retrofitted into existing winding operations. Light shielding must be constructed to ensure worker safety. In addition, controls should be integrated to provide proper operation and safety.