Forming of Thermoplastic-Matrix Composites

3 Simulations, Shape Categories, and Forming Machine Concepts. 422 

7 Forming Arbitrary Curved Shapes Without Dies. 435 

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Figure 14.4 Shape categories of components that might be formed from thermoplastic matrix composite materials...

Ramani K, Miller A K and Cutkosky M R. (1992) A New Approach to the Forming of Thermoplastic-Matrix Continuous-Fiber Composites Part 1 Process and Machine, J Thermopl Compos Mater 5 184-201,... 

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

The process by which a thermoplastic matrix composite consolidates to form a laminated structure has been attributed to autohesive bond formation at the ply interfaces. Autohesive bond formation is controlled by two mechanisms (1) intimate contact at the ply interfaces, and (2) diffusion of the polymer chains across the interface (healing). The rate of autohesive bond formation and hence the speed of the composite consolidation process is directly related to the temperature-pressure-time processing cycle. 

Another important application of thermoplastic fibers such as poly ether ether ketone (PEEK), Poly etherimide(PEI), and VectranM andHS (Vectranis the trade mark of Hoechst liquid crystalline polymer) is in making thermoplastic matrix composites. Commingled yams of the reinforcement and matrix such as quartz/PEEK, glass/PEI, Vectran HS/M are used to make the composites wherein the matrix yarn fuses to form the continuous phase of the composite. 

Mallon, P.J., O Bradaigh, C.M. and Pipes, R.B. (1989) Polymeric diaphragm forming of continuous fibre reinforced thermoplastic matrix composites. Composites, 20, 48-56. 

Both thermoplastics and thermosets can be formed by compression moulding (Fig. 24.5). The polymer, or mixture of resin and hardener, is heated and compressed between dies. The method is well suited to the forming of thermosets (casings for appliances, for instance) and of composites with a thermosetting matrix (car bumpers, for example). Since a thermoset can be removed while it is still hot, the cycle time is as short as 10 seconds for small components, 10 minutes for large tliick-walled mouldings. Pressures are lower than for injection mouldings, so the capital cost of the equipment is much less. 

If a ductile matrix is reinforced with brittle fibers as in most thermoplastic and metal matrix composites, the matrix forms bridges in the plane of the broken fibers and the work of matrix shearing / ms is given by (Cooper and Kelly, 1967 Tetelman, 1969 Cooper, 1970)... 

Finally, metal- and resin-bonded composites are also classified as particulate composites. Metal-bonded composites included structural parts, electrical contact materials, metal-cutting tools, and magnet materials and are formed by incorporating metallic or ceramic particulates such as WC, TiC, W, or Mo in metal matrixes through traditional powder metallurgical or casting techniques. Resin-bonded composites are composed of particulate fillers such as silica flour, wood flour, mica, or glass spheres in phenol-formaldehyde (Bakelite), epoxy, polyester, or thermoplastic matrixes. 

In multiphase filled polymer compositions, which may contain mixed filler types, combinations of fillers and fibres, or proportions of filler and a secondary modifying polymer, such as an elastomer, the spacial distribution of the phases has a direct bearing on the properties of the composite. In the case of the last mentioned system, the rubber may encapsulate the filler, be present as discrete droplets within the thermoplastic matrix or co-exist in both structural forms [80,81]. 

As can be seen from the results, the composite formed from monomer/-polymer 114a with Celion G30-500 8HS fabric exhibited excellent mechanical properties [28], To a first approximation it would appear that the inherent fracture toughness of the matrix resin has been carried over to the composite panels. The CAI (compressive strength after impact) and OHC (open hole compression) tests are a direct measurements of the toughness of the composite part, the value of 332 MPa for the CAI compares very favorably to the value of 300 MPa typical for the thermoplastic composites. The OHC values under hot-wet test conditions would seem to indicate that the composite has very good retention of its mechanical properties at both 177°C and 203 °C. 

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