Toughness improvement of carbon laminates by periodic interleaving thin thermoplastic films

Improved carbon fiber reinforced laminates for aerospace applications are usually made by toughened matrix resins based on epoxies. The toughness of these laminates is indirectly evaluated by residual compression strength after a low-velocity impact, which is often abbreviated to CAI. It is called the second generation of epoxy carbon composites which possesses a CAI value over 200 MPa. They prevail in the aerospace industry even though there are many other textile composites with significantly higher Z-direction strength. However, it is well-known that the toughness of the matrix resin cannot be completely transferred to the impact resistance of the laminate measured by CAI. And the layer to layer architecture of the laminates has an additional obvious influence on the impact resistance. We manufactured epoxy carbon laminates made of periodic and non-periodic interleaved thermoplastic thin films. It was the intention to study the relationship between the impact resistance and the interleaving structure for the structure optimization. This paper reports the results of the periodic interleaved one.