Sharif University of Technology Scientia Iranica 1026-3098 27 1 2020 02 01 Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube-reinforced polyimide using multi-scale FEM 252 261 21120 10.24200/sci.2018.5722.1444 EN M. Ahmadi Department of Mechanical Engineering, University of Guilan, Rasht, P.O. Box 3756, Iran. R. Ansari Department of Mechanical Engineering, University of Guilan, Rasht, P.O. Box 3756, Iran. H. Rouhi Department of Engineering Science, Faculty of Technology and Engineering, East of Guilan, University of Guilan, P.C. 44891-63157, Rudsar-Vajargah, Iran. Journal Article 2017 12 07 In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods. https://scientiairanica.sharif.edu/article_21120_35229ece51e9f88aebe66a8b0ab32c51.pdf