M. D. Wakeman

An integrated cost and consolidation model for commingled yarn based composites

In order to assess the potential of commingled yarns for cost-effective manufacturing of thermoplastic composites, an integrated cost and consolidation model has been developed. The cost estimation procedure and the consolidation model are applicable to a wide variety of composite processing techniques. Interaction between the cost and consolidation models allowed the determination of the processing conditions necessary to achieve the desired quality at a minimum manufacturing cost. It also permitted study of the material and cost responses to a particular set of processing parameters. This was illustrated for a generic composite hook manufactured by a novel technique, referred to as integrated processing, utilising robotic placement of commingled yarns of carbon and polyamide 12 fibres and over-injection moulding. Comparison with hooks processed by unreinforced polymer via injection moulding also demonstrated the potential of the integrated processing technique for the production of complex-shaped composites with increased performance-to-cost ratio.

Hybrid Glass Mat-reinforced Polypropylene-Montmorillonite Nanocomposites

Polypropylene/montmorillonite (iPP/MMT) has been investigated as an alternative to isotactic polypropylene (iPP) as a matrix for glass mat thermoplastic (GMT) composites. The melt viscosity increased significantly on MMT addition, but iPP/5.9 wt% MMT-based hybrid GMT preforms were fully impregnated after 30 s of compression molding, which is consistent with GMT industrial cycle times. The flexural modulus and strength increased monotonically with MMT content in consolidated hybrid GMT specimens prepared by compression molding, although the impact strength decreased. Moreover, the increases in the flexural modulus were greater than predicted from a conventional rule of mixtures taking into the measured Young’s moduli of the iPP/MMT matrices. Possible reasons for this are discussed.

Hybrid Glass Fiber-reinforced Thermoplastic Nanocomposites

The feasibility of integrating thermoplastic isotactic polypropylene/ montmorillonite nanocomposite matrices into conventional fiber-reinforced composites has been investigated. Two basic processing routes were considered: long glass fiber (GF)-reinforced composites based on co-wound or co-woven yarns and glass mat reinforced composites. In each case satisfactory impregnation and consolidation were demonstrated, although at high fiber contents, this required increased pressures and/or temperatures in the presence of the montmorillonite. Flexural tests on the glass mat reinforced composites, containing relatively low GF contents, showed the use of a nanocomposite matrix to lead to the significant improvements in bending stiffness and strength.