Single-Fibre Composites

Goda, K., Park, J. M. and Netravali, A. N., A new theory to obtain weibull fibre strength parameters from a single-fibre composite test, J. Mater. Sci., 30, 2722 (1995). 

Ochiai, S. (1999) Interfacial debonding in single fibre-composite with a cracked matrix - Part 1 Debonding during cooling. International Journal of Materials and Product Technology, 14, 147-166. 

Tsai CL, Daniel IM, Method for thermomechanical characterization of single fibres. Composites... 

Determination of fibre strain in single fibre composites by Raman... 

This method, proposed recently by Galiotis and co-workers [20], consists to apply a small deformation to a single fibre composite (see previous section) and to determine the fibre strain, due to stress transfer, by recording the Raman spectra of the fibre at different points x along this fibre. In fact, the location in wavenumber of some specific peaks of the fibre Raman spectrum is sensitive to the strain at which the fibre is subjected. Knowing the variation of the peak shift versus strain, previously determined on isolated fibres, it is thus easy to deduce the strain state of the fibre into the model composite. Furthermore, by a force balance equation on an element of the fibre, the shear stress Xx can be calculated at each point x by the following expression ... 

More modestly, to a first approach, the aim of the present part is to analyse the influence of the interfacial adhesion W on the magnitude of the fibre-to-matrix stress transfer capacity. For all the study, these interfacial stress transfer capacity is defined in term of interfacial shear strength x, measured by means of a fiagmentation test on single fibre composites. According to the previous part of this study, x is given by the following expression ... 

A tentative model has been proposed to relate the interfacial shear strength at the fibre-matrix interface, measured by a fragmentation test on single fibre composites, to the level of adhesion between both materials. This last quantity has been estimated from the surface properties of both the fibre and the matrix and was defined as the sum of dispersive and acid-base interactions. This new model clearly indicates that the micromechanical properties of a composites are mainly determined by the level of physical interactions established at the fibre-matrix interface and, in particular, by electron acceptor-donor interactions. Moreover, to a first approximation, our model is able to explain the stress transfer phenomenon through interfacial layers, such as crystalline interphases in semi-crystalline matrices and interphases of reduced mobility in elastomeric matrices. An estimation of the elastic moduli of these interphases can also be proposed. Furthermore, recent work [21] has shown that the level of interfacial adhesion plays a major role on the final performances (tensile, transverse and compressive strengths and strains) of unidirectional carbon fibre-PEEK composites. 

ElM Asloun, M Nardin, J Schultz. Stress transfer in single-fibre composites effect of adhesion, elastic modulus of fibre and matrix, and polymer chain mobility. J Mater Sci 24 1835-1844, 1989. 

Fig. 18 Single fibre composite specimen. The polyDCHD fibre Is located at the centre of the specimen while the resistive strain gauge is attached to the outer surface.

Fig. 4 Example of a model single fibre composite comprising a polypropylene fibre embedded in a polypropylene matrix, achieved by physically constraining the fibre to prevent melting. Reproduced with kind permission from Elsevier from [56]...

Figure 8.12 E>erived variation of fibre strain with distance along the Kevlar 149 fibre in a single-fibre composite tensile specimen at different indicated levels of matrix strain e (after [38])...

Termonia, Y., Theoretical study of the stress transfer in single fibre composites. J. Mater. Sci., 22, 504-508 (1987). 

---