Optimisation des parametres de mise en forme du composite peek/fibre de carbone

• Main Author: Ben Daly, Hachmi
• Format: Dissertation
• Language: French
• Subjects: plastics technology
• ISBN: 0315864109; 9780315864108

The objective of this work is the study of the effects of the processing conditions such as molding temperature, residence time and cooling rate on the crystallization kinetics and fibre/matrix interactions in the PEEK/carbone composite made from both a prepreg and a comingled fabric.
As first step, the moulding cycle has been simulated by differential scanning calorimetry, DSC. This simulation attempts to investigate the crystallization behaviour of the PEEK matrix in presence of the carbon fibre as a function of time/temperature conditions equivalent to those faced during the processing.
The large cooling rate range investigated in this study has demonstrated that the activation energy related to the crystallization process depends on the cooling rate.
In the second stage of this work, the influence of different time/temperature parameters of the molding cycle on the matrix morphology was investigated as well as the matrix/fibre interaction in the molded laminate.
The study of the crystalline structure of the PEEK matrix using scanning electron microscope reveals that the rise of the cooling rate increases the number of the nucleation sites and decreases the size of the crystalline entities. Moreover, longer residence time in the molding temperature results in an increase of the size of these entities.
The interfacial strength in the composite, evaluated by short beam shear test, was also found to be significantly influenced by the molding parameters.
Annealing performed on the rapidly cooled specimen which lead to an increase of matrix crystallinity shows that although interfacial crystallinity is essential to assure optimum interfacial strength, it is not the primary parameter responsible for efficient fiber/matrix interaction. Actually, improvement occurs only for laminates in which strong fibre/matrix interaction is created during the molding process; provided that the molding temperature is high and the residence time is long. (Abstract shortened by UMI.)