Filament Winding

Filament winding creates high-strength, axisymmetric composite shells by winding resin-impregnated fibers onto a rotating mandrel for pressure vessels and tubular structures.

Overview

Filament winding (fiber winding) builds composite parts by tensioning continuous fibers over a rotating mandrel while applying resin, then curing into a high-strength shell. The process excels at axisymmetric parts—tubes, tanks, pressure vessels—where fiber angles and layer counts can be precisely controlled to match load paths. It delivers very high fiber volume fractions, excellent hoop and axial strength, and repeatable wall thickness over long lengths.

Choose filament winding for cylindrical or spherical parts that see internal pressure, torsion, or bending, and when you need consistent properties across medium to high production volumes. You trade geometric freedom for performance and cost efficiency: through-holes, sharp transitions, and integrated fittings are difficult and usually added by secondary machining or bonded hardware. Tooling is relatively simple (mandrels), but design must respect fiber steering limits and demolding. Expect excellent structural performance and weight savings, but limited suitability for complex 3D shapes or heavy localized features.

Common Materials

  • Carbon fiber / epoxy
  • E-glass fiber / epoxy
  • E-glass fiber / polyester
  • Aramid fiber / epoxy
  • Basalt fiber / epoxy

Tolerances

Typically ±0.010" on OD and wall thickness, ±0.020" on length with controlled winding and post-machining of ends.

Applications

  • High-pressure gas cylinders
  • Composite pressure vessels and tanks
  • Fiber-reinforced pipes and risers
  • Composite drive shafts
  • Rocket motor and solid propellant casings
  • Utility poles and masts

When to Choose Filament Winding

Use filament winding for primarily cylindrical or spherical composite parts that need high strength-to-weight and well-controlled hoop/axial properties. It fits best when you have repeatable designs, modest geometry variation, and medium to high volumes where mandrel tooling cost can be amortized. It is especially effective for pressure vessels, pipes, and shafts where fiber angles can be optimized for known load cases.

vs Resin Transfer Molding

Choose filament winding over resin transfer molding when the part is axisymmetric and dominated by hoop/axial loads, and you want very high fiber volume and tightly controlled fiber orientation. Winding is usually more efficient for long tubes and vessels with consistent cross-section, while avoiding complex matched molds and more elaborate RTM tooling.

vs Vacuum-Assisted Resin Transfer (VARTM)

Use filament winding instead of VARTM when you need repeatable, automated fiber placement on cylindrical parts and minimal variability in laminate quality. Winding offers better control of fiber tension and angle on round geometries, with less dependence on bagging skill and flow media design.

vs Prepreg Layup with Autoclave

Choose filament winding over prepreg/autoclave layup for high-volume, axisymmetric structures where automation and material utilization matter more than extreme geometric freedom. Winding provides excellent mechanical performance at lower labor content and tooling complexity, especially for tanks and tubes where hand-laid prepreg would be slow and costly.

vs Pultrusion

Select filament winding instead of pultrusion when you need a closed, pressure-capable cylinder or variable fiber angles rather than constant unidirectional fibers. Winding supports circumferential and helical orientations tailored to pressure and torsion, whereas pultrusion is limited to straight, constant-section profiles with mostly axial fibers.

Design Considerations

  • Keep parts primarily axisymmetric with smooth transitions; avoid abrupt diameter changes, sharp shoulders, and complex local features that disrupt fiber paths
  • Define required hoop and axial strengths so the shop can choose winding angles, sequence, and thickness rather than overbuilding conservatively
  • Specify realistic tolerances for OD, wall, and length, and allow post-machining on ends or interfaces where tight fits are critical
  • Plan mandrel design for removal: include draft, collapsible or soluble mandrels, and avoid undercuts that trap the tool
  • Consolidate metal hardware into a few robust attachment zones that can be bonded or overwrapped instead of many small bosses and penetrations
  • Provide load cases, operating pressure, temperature, and safety factors so the winder can optimize laminate schedule and resin system for durability and fatigue