Question

1. Describe and compare TWO methods used for the manufacture of Polymer Matrix Composites and discuss why these methods are easier and less expensive compared with metal matrix composites and (2x5) ceramic matrix composites Total Marks [10]

Answer 1

A polymer matrix composite is a material made stronger by adding fibers or particles to it. For example epoxy resin reinforced with glass fibers and polymer matrix composites with continuous carbon fibers. They are used for aerospace, automobile, and civil structures.

There are several methods used in the manufacturing of Polymer Matrix Composites.

i) Injection Molding

SCHEMATIC DIAGRAM CLAMPING PRESS RESIN-INJECTION MACHINE MOLD PART AIR OUT RESIN IN BI MOLD CLAMPING PRESS WOVEN FIBER- PLACED IN MOLD PRIOR TO INJECTION Preform Tool Cure Demold Injection Rosin

It is suitable for thermoplastic resin systems. Woven Fiber is placed into the mold prior to the injection. The resin mix is first heated in an injection chamber comprised of screw mechanism and then forced into the closed mold cavity under high pressure through the nozzle and is allowed to cure. It is suitable for fabrication of small to medium size parts such as valves, gears, instrument panels, etc

ii) Matched-Die Molding Methods

It Consist of compression molding, cold stamp molding and press molding

In this technique is molds are usually fabricated with cast iron, steel or aluminium alloy.

cvent ports moulded part moulds release agent gel coat NIZE ZUM moulding composite

compression molding

laminate sheared bbbdd poooo OO cold roller hot roller laminate stack RF FF resin film fibre fabric

Cold stamp molding

vacuum bleeder teflon film >> peel ply bleeder composite lay-up

Press molding

Difference between Injection Molding and Matched-Die Molding Methods are

In the former method resin is heated and brought into liquid form whereas in matched die methods, resin in in its original form.

Former method uses injection technique, molten resin is injected into reinforcements in a closed mold whereas in the latter method, compression or pressing is used to join resins with the reinforcements.

These methods are easier and less expensive compared with metal matrix composites and ceramic matrix composites

These methods are easier and less expensive compared with metal matrix composites and ceramic matrix composites as we know that both the methods use the polymer in either molten state or in some kind of deformed shape. It is less expensive to grind, crush and melt polymers then the metals and ceramics.
Also sustaining high temperatures and maintaining peripheral equipment requires much high costs dealing with metals and ceramics owing to there extreme properties than the polymers.