Which manufacturing method is used to create composite material profiles with a constant cross-section by pulling resin through a die?

• A. Filament winding
• B. Pultrusion
• C. Compression molding
• D. Injection molding

Answer: (B)

Pultrusion is a continuous composite manufacturing process in which reinforcing fibers are pulled through resin impregnation and a heated die to shape and cure the material. The die defines a fixed cross-sectional geometry, so as the material is drawn through, the cross-section remains identical along the entire length. This makes it ideal for producing long, uniform profiles like beams, channels, angles, and rods with consistent fiber alignment and resin content.

Imagine fibers (glass, carbon, or similar) being pulled through a resin bath or pre-impregnated with resin, then through a heated die that sets the shape. The pulling action and the curing in the die ensure a constant cross-section from start to finish, enabling continuous lengths with predictable mechanical properties.

Other methods don’t create that fixed cross-section along a long length. Filament winding builds around a form to make hollow or closed shells, often with a circular or curved cross-section, and not by pulling through a shaping die. Compression molding and injection molding shape parts in molds with heat and pressure, but they’re typically used for shorter pieces or single, complex shapes rather than long, uniform profiles.