Structure and properties of carbon fibre reinforced aromatic thermoplastics
In common with all composite materials, Aromatic Polymer Composite-2 (APC-2) is inherently expensive and as such any reclaimed material is potentially extremely valuable. In this work, pieces varying from 6.35-25.^mm square (0.25-1.Oinch) were cut from APC-2 single ply prepreg of thickness 0.125mm and compression moulded into panels 150mm square, with the thickness controlled to meet the requirements of subsequent characterisation. Further work was carried out on panels of the same dimensions moulded from squares cut from 8 ply preconsolidated APC-2, the size of these squares ranging from IQ- 25. 4mm square. The flexural, tensile and compressive mechanical properties, fracture and impact toughness, and creep behaviour of these composites were determined, as a function of particle size. Finally, the potential for moulding was assessed. Results from tensile and flexural tests show that the variations in the tensile and flexural moduli of the composites increase linearly with particle size. Using suitable modifications of planar reinforcement theory to produce a quasi-isotropic theory, an accurate prediction of the experimental values is possible, from the Modulus Reduction Factor [MRF]. A similar approach with respect to the experimental strength can only be made if the mode of failure is known. The fracture toughness of the composite moulded from single ply prepreg was found to be greater than that of continuous fibre reinforced APC-2 and increased with decreasing particle size over the size range examined. Fractographic analysis of this phenomenon revealed several toughening mechanisms: Polyetheretherketone (PEEK) rich zones act as crack arresters; fibre bundle and particle bridging of the crack increase the work to fracture. Impact toughness is greatly enhanced over injection moulded composites for similar reasons. The creep property profile is very promising and shows retention of the creep resistance of PEEK and carbon fibre. The formability shows a possible opportunity for component manufacture otherwise impossible at present.
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