Manufacturers of composite materials have been developing high strength fiber rein forced composites with thermoplastic matrix systems exhibiting enhanced performance in fracture toughness and damage tolerance with the potential of reduced manufacturing cost for both primary and secondary structure components. A review will be made of principal thermoplastic matrix systems and processing methods used to fabricate the fiber rein forced composites, which have been developed during recent years. Included is a com parison of the neat matrix resins' chemical structure, thermal/tensile properties, fracture toughness, melt viscosity, solvent resistance, morphology and melt processability. The matrix-dominated mechanical properties of thermoplastic composites are given, including flexural, short beam shear and compression strengths, interlaminar fracture toughness and/or compression-after-impact performance. Innovative process development in thermoplastic composites including thermoformable sheets, filament windi...

Recent Development in Thermoplastic Composites: A Review of Matrix Systems and Processing Methods

A polypropylene (PP) powder impregnated glass fiber (GF) bundle system was selected to investigate the relationships between impregnation mechanisms and pro cessing conditions during consolidation of these materials. Microscopy of cross-sections and density measurements helped to examine the quality of impregnation and consolida tion. Based on microscopic observations and previously developed processing theories, an impregnation model for the qualitative description of the consolidation behavior in lami nates made out of these materials is generated. It can be used to describe variations in void content over the laminate thickness as a function of bundle geometry and combinations of processing variables. The relationships between processing temperature, holding time and applied pressure required to reach full consolidation were evaluated. Results of transverse flexural tests are used to correlate the mechanical properties with the impregnation quality, in particular the void content in the laminates. Fina...

Impregnation and Consolidation in Composites Made of GF/PP Powder Impregnated Bundles:

Bending of fibre-reinforced thermoplastic sheets

Numerical analysis of stresses and deformations in composite materials sheet forming: central indentation of a circular sheet

A literature survey is presented on sheet-forming methods and mechanisms for continuous fiber reinforced thermoplastics. The diaphragm forming process is shown to be one of the more promising fabrication routes for complex-curvature structures. The primary deformation mechanisms involved in the sheet-forming processes are identified and discussed. Earlier approaches to develop mathematical models either have been kinematically based or have treated only one of the primary deformation mechanisms. A promising constitutive model for the highly anisotropic behavior of the composite at forming temperature is examined. The composite sheet is assumed to behave as a transversely isotropic Newtonian fluid that is both incompressible and inextensible in the fiber direction. The second section of the paper treats the experimental development of the polymeric diaphragm forming process for thermoplastic composites. The viscoelastic properties of the diaphragm material are characterized by dynamic mechanical analysis. The rate sensitivity of the phenomenon of shear-buckling during forming of certain cross-ply and quasi-isotropic composite laminates is investigated, using a shallow female mold. Finally, the interface condition between the diaphragm and the composite during forming is examined.

Issues in diaphragm forming of continuous fiber reinforced thermoplastic composites

By combining techniques of explosive welding and cladding and shock wave compaction and consolidation of powders, a fabrication technology has been developed for consolidating, bonding, and encapsulating reactive and temperamental copper oxide-based high-Tc superconducting powders in a supporting metal matrix. These ceramic superconductor/metal matrix composites have unique features as precursors to a range of superconductor devices and applications. The fabrication strategy utilizes a concept of prototype manufacturing where processed superconductors are characterized and tested to optimize the process variables and reliable behavior. This strategy, may lead to early commercialization and applications for the new high-Tc oxide superconductors.

A.W. Hare

Papers

Fabrication of metal/high-temperature superconductor composites by shock compression