Effect of clearance and pressure on matrix flow in U bending of epoxy/carbon fibre composites

Abstract

The depletion of fossil fuels is forcing the automotive, aerospace and transport industries to focus on increasing both energy efficiency and mileage per unit of fuel consumed. To this end, many fibre reinforced composite materials have been adopted. Among these, carbon fibre reinforced plastic (CFRP) is one of the most attractive materials given its high strength and rigidity. The mechanical properties of CFRP are influenced greatly by the fractions of reinforcements and matrix. In this study, a CFRP U channel was produced by hot compression moulding. The epoxy fraction was measured at different pressures and clearances. It was found that clearance is important for determining the mechanical properties and epoxy flow. When the clearance is ≧1, the mechanical properties at the side positions decrease to 250–400 MPa. For the clearance of 0·7, the thickness at the side positions decreases, thus allowing the bending stress to increase to 790–800 MPa. Macroscopic observation of the epoxy flow shows that clearance plays a dominant role in epoxy flow behaviour within the mould cavity and excessive pressure causes large quantities of epoxy to flow out of the mould.

Keywords:

• Carbon fibres
• Mechanical properties
• Compression moulding
• Resin flow

Acknowledgements

This work was supported by the Advanced Technology Center Project (grant no. 10039031, The Development of the Manufacturing Process for the High strength Steel and Composite Materials) funded by the Ministry of Knowledge Economy (MKE, Korea) and by a human resources development grant of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), funded by the Government of South Korea, Ministry of Knowledge Economy (grant no. 20104010100540).