Caracterisation mecanique des composites a renfort tresse et application aux ressorts helicoidaux.

摘要

The aim of this work is to characterize and study the mechanical behavior of axisymmetric braided composite tubes and springs manufactured by a new process, which consists of the injection of an epoxy resin in a mold containing braided fiber-glass reinforcement. Some adjustments were realized on the manufacturing process to improve the quality of the products. The quality control showed that, after these adjustments, a noticeable improvement in the physical and mechanical properties could be obtained. Moreover, other adjustments were proposed in order to improve the quality of the manufactured composite springs.; Compressive and torsion tests were conducted on the composite tubes. In compression loading, the tubes failed in pure shear due to fiber micro-buckling accompanied, in some cases, by an extension of the matrix in the transverse direction. However, the tubes resisted to the maximum torque applied by the test machine, and consequently did not fail under torsion loading. However, the modulus and the minimum strength were estimated.; The tests showed that the springs could not fail under compressive loading because of the displacement of the test machine limited to 100 mm, which is smaller than the failure displacement of the springs.; Finally, a comparison between the predicted and experimental mechanical properties of the tubes and springs showed that the Tasi-Wu and Tsai-Hill failure criteria are not applicable for this type of materials.