Fibre-reinforced plastic composite deformability

An advantage of these composites is the increased resistance to fibre damage during composite processing which results from the intrinsic ductility of metallic fibres and the possibility of exploiting their plastic deformation for composite toughness enhancement [100]. A penalty is paid due to the relatively low thermal capability and poor chemical resistance of the metallic fibre reinforcement, limiting the application temperature and environment. 

In the case of unidirectional (or longitudinal) fibre reinforced composites, the stress is transferred from the matrix to the fibre by shear. When stressed in tension, both the fibre and the matrix elongate equally according to the principle of combined action [14]. Hence, the mechanical properties of the composite can be evaluated on the basis of the properties of the individual constituents. For a given elongation of the composite, both constituents, fibre and matrix, may be in elastic deformation the fibre may be in elastic deformation whereas the matrix may be in plastic deformation, or both the fibre and the matrix may be in plastic deformation (Fig. 19.3). 

FIGURE 4. SEM micrograph of the fracture surface of a soda-lime glass matrix composite reinforced by stainless steel fibres. The fracture surface exhibits fibre pull-out and partial plastic deformation of the fibres. (Micrograph reproduced with permission from Ref. [6]). 

Figure 8 shows a typical fracture surface of a glass matrix composite reinforced by short stainless steel fibres [16]. It is apparent that the fibre was intercepted and sectioned by the propagating crack and there is some evidence of plastic deformation. 

The eomposite strueture design involving orientation of the fibres in the matrix is an important faetor in fibre-reinforeed composite fabrication. Since CNTs can be deformed plastieally by the applieation of external forces, plastic working such as drawing and extrusion can be applied for the production of composites. In this seetion, the preparation of the CNT reinforced nanocrystalline C o matrix composite by the drawing process is presented, followed by a description of the composite structure and mechanical characteristics. ... 

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