Stiffness Determination of Bi- and Triaxial Flat Braided Carbon/Vinyl Ester Composites Using Micromechanics Method

This paper is concerned with geometric modelling and elastic properties of 2D biaxial and triaxial braided composites. A representative unit cell (RUC) of braid architectures is first identified along with its constituents. Geometric parameters of braided structures are compared with each other. A method of inclusions with the Mori-Tanaka homogenisation was used in the determination of elastic properties of the unit cell with the Tex-Comp software. As a result, a higher amount of crimp occurs in triaxial braided structures compared to biaxial structures generated using the same yarn and construction. Therefore, the elastic modulus of the triaxial structure diminishes compared to that of the biaxial structure. However, the axial yarn reinforcement in triaxial structures ensures four times higher axial strength in the axial direction related to the biaxial structures that it provides. The results were experimentally verified. Avtor članka obravnava geometrijsko modeliranje in elastične lastnosti dvoosnih in triosnih pletenih kompozitov. Najprej je identificirana reprezentativna osnovna celica (RUC) pletenih struktur, vključno s sestavnimi deli. Primerjani so geometrijski parametri pletenih struktur. Pri določanju elastičnih lastnosti osnovne celice je bila s pomočjo programske opreme Tex-Comp uporabljena metoda vključkov z Mori-Tanaka homogenizacijo. Rezultati kažejo, da je pri triosnih pletenih strukturah več kodranja kot pri dvoosnih strukturah, izdelanih iz enakih prej in z enako vezavo. Zato se modul elastičnosti triosne strukture v primerjavi z dvoosno strukturo zmanjša. Kljub temu ojačitev v smeri osi preje pri triosnih strukturah zagotavlja štirikrat večjo trdnost v smeri kot pri dvoosnih strukturah. Rezultati so bili potrjeni s poskusi.