Application of synchrotron radiation micro-CT to local morphological and numerical characterization of short fibre reinforced polymer composites.

In components of short glass fibre reinforced polymer obtained by injection moulding, processing conditions produce complex orientation patterns that influence the mechanical properties of the component. Computed microtomography with synchrotron radiation constitutes the ideal analysis non destructive technique, being able to provide high resolution images of the internal structure of the material. In particular, the source high spatial coherence available at Elettra (Trieste) makes is possible to apply imaging techniques that exploit also information of the phase shifts induced by the sample inhomogeneities. These techniques are effective to detect even small details, such as short reinforce fibres within a polymeric matrix. Given fibre numerosity in our samples, instead of trying to isolate each single fibre and measure its geometrical properties from the 3D micro-CT reconstructions, we choose to compute global anisotropy parameters, commonly employed in other fields such as biomechanics or geology. Mean Intercept Length (MIL) and the related fabric tensor were used to assess local fibre orientation variations and to interpreter fatigue tests results in the light of different fibre orientation distributions. The problem of whether a morphological description can be predictive of the local elastic behaviour of these materials has also been addressed.