Composite Materials Bill Pedersen Components of Polymer Composites

Composite Materials Bill Pedersen

Components of Polymer Composites Polymer Resin n Usually a thermoset Epoxy Polyester Vinylester n Thermoplastics Aerospace Reinforcing fiber n Fiberglass E, S, C (E most common) n n n Graphite (Carbon) Aramid (Kevlar) Spectra (PE)

Open Molding Female Mold of part n n n Made of FRP (Fiberglass Reinforced Polymer) Has steel supports Gel coated and waxed To make part: n n Gel coat mold Spray on chop fibers, resin and catalyst Roll out air Add stiffeners or layers as desired

Vacuum Bagging Greatly reduced VOC (Volatile Organic Content) (Reduced emissions) Cover reinforcement with cheap plastic cover Suck resin into the part to fill the void

Making a Kayak

Open vs. Closed Molding Open Molding n n As shown previously Only one sided mold Limited temperature control Lower capital cost for molds Closed molding – or compression molding n n Two sided mold – part is sandwiched between two mold halves Pressure applied Improved material properties (fewer voids) Higher Capital cost

Closed Molding Can be done using Prepreg or wet layup Process: n n Resin impregnated fibers cut to proper geometry Heated Die sets close on part Part is cured at temperature Die opens and part is ejected from mold

Filament Winding Control the orientation of the fiber using a relative motion of rotation and linear motion Example Products: n n Pressure Vessels Fishing Poles Light Poles Antennas

Pultrusion Fibers or cloth are pulled through a resin bath Heated in a die with a shaped profile Cured to shape Cut to length

Metal Matrix Composites Completely different field. The book has them in the same chapter, but they are very different. Combination of metal matrix, with ceramic reinforcement. Examples: n n Titanium with Si. C fiber reinforcement Mg with Si. C discontinuous reinforcement