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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Toughening of composites for liquid composite moulding

Author: THANOMSILP, Chuleeporn

Year: 2001

Supervisor(s): Paul Hogg

An investigation into toughening composites for liquid composite moulding (LCM) has been carried out. The LCM process requires a low viscosity resin, which tends to be brittle. A concept for toughening the final composite part by incorporating toughening additives in the preform was investigated. The specific idea examined was to include low cost thermoplastic fibres in the fabric, commingle into the structured fibres. Commingled yarn fabrics that are composed of glass fibres blended with thermoplastic fibres were used as a preform. Various types of thermoplastic fibres such as polypropylene (PP), polyamide (PA) and modified polyethylene terephthalate (mPET) were studied. Varieties of hybrid composites were made from the combination of these fabrics with different resins such as polyester resin, Cycom X823 RTM epoxy resin, and Shell Epikote 828 epoxy resin.
The properties of the hydride composites and also the plain glass fibre composites were investigated in various aspects concerning the toughness of the composites including the interlaminar fracture toughness, the penetration impact resistance, and the damage tolerance by compression after impact.

The results have shown that the hybrid composites based on the commingled yarn fabrics give a positive route for toughening composite for liquid composite moulding. The fibre-hydride composites such as GFPP and GFPA exhibited an improvement of penetration impact resistance compared to plain glass fibre composites. Although the interlaminar fracture toughness, impact damage resistance, and damage tolerance of these composites were decreased. In contrast, the matrix-hybrid composites such as GFmPET revealed higher interlaminar fracture toughness than the plain glass fibre composite. The GFmPET composites produced smaller impact damage areas than the plain glass fibre composites under the same impact energy.