This paper presents the influence of fibers on crystallization kinetics and on matrix morphology for poly(pheny1ene sulfide)/carbon composite. The following parameters were also considered: thermal stability, fusion/crystallization conditions and surface treatment of carbon fibers. In order to correlate these results with mechanical properties, composite samples were prepared and tested in both static and dynamic modes. The delamination resistance of the composite in shear Mode I1 is also discussed.
Twenty-two cases of vascular graft failures (thrombosis, pseudoaneurysm, dilation, infection) were investigated by means of physicochemical, histological, and ultrastructural studies. A general decrease of mechanical resistance to stress of the prostheses was observed. Its magnitude ranged from 2 to 75% of the values of identical virgin prostheses and there was no relation with the duration of implantation. In addition to the breakage of yarn filaments (SEM), migration of fiber debris (histology) was observed in 7 cases. The structure of the polyester molecule had evolved after implantation. A decrease of crystallinity (x-ray diffraction and differential scanning calorimetry) was noted. These observations raise the question of the established stability of vascular prostheses and emphasize the need for further investigations in human graft retrieval programs.
Dynamic viscoelastic analysis was used to continuously follow the "cold crystallisation" of poly(ethy1ene terephthalate) (PET) test bars. Samples which were cut from an amorphous PET sheet were heated to a given temperature in a hot cell. The evolution of the real part of the modulus not only allows the kinetic crystallisation parameters but also the nucleation and growth characteristics to be determined. This method was applied to unidirectional PET/glass fibre composite strips. Thus, the influence of the glass fibres on the morphological and kinetic characteristics of the matrix crystallisation has been investigated.
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