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Abstract
The object of this thesis is the study of the response to normal compaction of plane textile reinforcements produced by assembling rovings made of continuous fibers and used for the manufacturing of composite parts. In the first part, the effects on the compaction behavior of the principal processing parameters related to the reinforcement, and modulated during the fabrication of the composite parts, are investigated.
In the second part, quantities are introduced which allow the construction of geometric definitions of the reinforcements. The quantities are defined at two levels, i.e. for the textiles and for the rovings.
The study of the compaction behavior of the reinforcements were made in a context of small-series production, the two manufacturing processes considered being closed-cavity molding for middle-sized parts produced for semi-structural applications, and autoclave consolidation of stacks of thin preimpregnated ribbons for large parts requiring higher levels of performance.
The mechanical properties of textile reinforcements have a major impact on the kinetics of certain processes such as the injection-compression, infusion molding, or impregnation of textiles by calendering. In the first case, the injection of the resin happens prior to the compaction of the reinforcement. In the second case, the final thickness of the laminate depends almost exclusively on the compaction behavior of the reinforcements. In the third case, no restriction is imposed on the preimpregnated sheet's thickness at the exit of the calender.
The reinforcements used for the production of middle-sized series of parts are often assembled in preforms prior to the molding operation. The obtention of structural parts featuring high fiber volume fractions requires important levels of compaction to be applied on the preform. Consequently, the obtention of satisfactory preforms in which the layout of the fibers is controlled requires, among other information, the knowledge of the compaction behavior of the reinforcements.
The results of a first experimental program structured toward the objectives of the thesis are presented. This program demonstrates that the processing parameters having the strongest effect on the behaviors in compression and relaxation are not the same (the compaction rate and fluid saturation for relaxation, and the cycle number for compaction).
The reorganization kinetics of heterogeneous networks is described. The results demonstrate that the application of ten successive compaction cycles allows an important reduction of some resin-rich areas in the final parts, the majority of this reduction being obtained after five cycles.
Chapter 6 presents some geometric quantities used to define woven, braided and warp-knitted textiles. The parameters defining the architecture of these textiles are introduced briefly, and some applications are discussed. (Abstract shortened by UMI.)
