Through the application of theoretical analysis and experimental characterization, the influence of fiber architecture on the mechanical and thermal properties of braided hybrid composites is investigated. Braid angle and fiber volume fraction are considered as the essential factors that affect the performance of braided hybrid composites. The effects of the axial yarn stiffness, axial yarn volume fraction, and braid angle on composite axial-tensile, transverse tensile, bending, and compression behavior have been examined experimentally. Finally, the thermal behavior is studied using dynamic-mechanical analysis. The results have shown that the axial mechanical response of triaxially braided composites depends on the mechanical properties of the axial yarn and its volume fraction, as well as the braid angle.
Braided composites made of stiffer axial yarns possess a higher axial tensile and bending modulus.
Furthermore, the ultimate strain of the composites depends on the ultimate strain of the axial yarn. When the volume fraction of the axial yarn is larger, the triaxially braided composites are stiffer and stronger, and they have a larger ultimate strain. The study of the braid angle effect on the mechanical behavior of triaxially braided composites has shown that for 70 and 55 braid angle specimens, the normalized stress-strain curves are very similar. The thermal response of triaxially braided composites depend upon the response of the axial yarn to the thermal changes. Finally, the application of classic laminated plate theory to study the effect of the axial yarn on the mechanical behavior of triaxially braided hybrid composites has demonstrated that the axial yarn stiffness at low fiber volume fraction affects the mechanical properties only in the axial direction.