Évaluation des performances mécaniques de raidisseurs en "T" carbone-époxy préformés à l'aide de la couture "one-sided"

Abstract

To reduce cycle time and the variability of composite parts, "One-Sided Stitching®" is studied as an assembly method for laminates. This work is part of a larger research project, COMP-501, which goal is to demonstrating the textile preforming process and the transition of preforms into composite part using VARI. The major milestones of the COMP-501 project to study the influence of stitching are typical with the "building-block approach." The influence of the preforming technique was first studied on flat plates and the results were used to select the sewing parameters for the latter steps. For the second phase of the project, the study of stitching on T-stiffeners, the objectives were to select a preferred stitching pattern and to evaluate the influence of the stitching on the mechanical properties. This work evaluated the influence of the position and orientation of the stitching using web tear-off tests and three-point bending test. Five initial stitching patterns were evaluated in order to select a preferred pattern. Using the preferred pattern, the influence of stitching on the buckling behavior and damage tolerance were then studied. The results of these tests were used for the final stage of the project: the production of the demonstrator panel. The web tear-off tests have demonstrated that a stitch located near the noodle significantly reduces the resistance of the joint by creating distortions near the fragile noodle region. However, one of the patterns showed a slight increase in tear-off strength with an asymmetric loading. It is assumed that the increase in flexural stiffness of the nearby laminates reduces the stress on the region of the noodle. Three-point bending tests showed that a stitch near the noodle increases the rigidity of the element ensuring a better distribution of the load between the web and the flange. The results were used to design a new stitching pattern with the stitches located away from the fragile noodle in order to limit the creation of distortions which reduce the strength of the stiffener. The behavior of a stiffener axially loaded and damage tolerance were also verified. The stitching does not appear to have a significant influence on the failure mode or the residual strength of the stringer. Sewing, being very local, hardly affects the overall behavior of a structure.

Date	4 Jan 2016
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Simon Joncas (Supervisor)