Mohammad Rouhi

The effect of the percentage of steered plies on the bending-induced buckling performance of a variable stiffness composite cylinder

Abstract The fiber steering capability of automated fiber placement machines offers the designers more room to fully exploit the directional properties of composite materials. Circumferential stiffness tailoring by fiber steering can considerably increase the bending-induced buckling performance of laminated composite cylinders. The potential structural improvement resulting from fiber steering depends on different design parameters such as the number of plies considered for fiber steering in a laminate. In this study, the buckling performance improvement of a variable stiffness (VS) composite cylinder is investigated for different percentages of plies considered for fiber steering in a multilayered composite laminate. A surrogate-based modeling along with a multi-step optimization is used in the design procedure of this study. The improvements in the buckling performance are shown and verified using finite element analysis in ABAQUS software. The mechanisms leading to buckling performance improvement of VS composites are also investigated and presented for different percentages of fiber-steered plies.

10 – Influence of interphase and inclusion waviness on stiffness properties of a nanoenhanced matrix

Abstract Micromechanical modeling approaches are used to investigate the effects of carbon nanofiber (CNF) waviness and the matrix–fiber interphase region on the stiffness properties of a nanoenhanced thermoset polymer matrix. The interphase region is modeled using the multi-inclusion approach, and the effects of its mechanical properties and profile on the overall elastic properties of the nanoenhanced matrix are calculated. Moreover, the effect of waviness is explored by varying the wavelength and amplitude of a sinusoidal model.