Mechanical properties of biaxial carbon fibre laminate

Abstract

In this thesis we will try to narrow down how lamination techniques affect the mechanical properties of a biaxial carbon fibre laminate. This will be done by conducting an experiment where three laminates are produced using three different lamination techniques. The techniques used for the experiment are prepreg, wet lay-up, and vacuum infused lamination. In the wet lay-up technique, the fibre reinforcement layers are put down by hand and the resin is added with a brush or a roller in between each layer. In vacuum infused lamination the fibre reinforcements are staked, and vacuum pressure is used to push the resin into the fibre. Prepreg is a semi-ready product, where the resin is already impregnated into the fibres during the manufacturing process, so when making a part the prepreg just needs to be put under vacuum and in an oven during curing. All three laminates will be made from 5 layers of carbon fibre mat/pre-preg. The mat and prepreg is 400g/m2 biaxial that both has an orientation of ±45°. The wet lay-up and vacuum infused lamination will also be laminated with the same epoxy while the prepreg is already impregnated with an epoxy resin matrix during its production. The laminates are cut into 5 sample pieces per laminate according to the ISO 14125 standard and the samples are tested with a three-point bending machine according to the same ISO standard. The results showed that the prepreg and the vacuum infused lamination have a higher flexural modulus, fibre volume fraction and maximum flexural strength, while wet lay-up had the maximum force. This is due to the prepreg, and vacuum infused lamination samples were 1 mm thinner and 3 g lighter when cured. A materials thickness has a significant impact on its flexural strength, since thicker materials have a higher moment of inertia which gives them a higher resistant to bending and flexural strength. A material with a higher moment of inertia can endure more force. This is why the vacuum infused lamination and the prepreg have a higher flexural modulus than the wet lay-up since there is a difference in thickness. So, we can see that putting laminates under vacuum has had the most distinct effect on the mechanical properties.