Bladder Molding

Bladder Molding

For Most Hollow Composite Structures Other than a Simple Tube ▪ Complex Geometries ▪ Cosmetic Finishes

What is the bladder molding process?

We start with sheets of pre-impregnated fibers called "pre-preg."

  1. The sheets are wrapped around an inflatable bladder and then placed inside a mold cavity
  2. Once the mold is closed, pressure is applied to the inside of the bladder causing the bladder to expand pushing the pre-preg outward against the inside of the mold cavity
  3. Heat is then applied to the mold to solidify or "cure" the composite in the shape of the inside of the mold cavity

After curing, the mold is opened revealing the hardened hollow structure at which time the bladder is removed (typically) from the inside of the cured part.

When do we use this process?

Bladder molding is used for parts that either have complex geometry, strict cosmetic requirements, tight outside tolerances or a combination of all three.

Parts can be too complex for this method, in which case multiple tools are used to create separate components that then get bonded together in post processing, e.g., bicycle frames.