Hossein Ghayoor

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.

Effect of in situ treatment on the quality of flat thermoplastic composite plates made by automated fiber placement (AFP)

Abstract Composite structures used as aerosurfaces in aerodynamic applications are required to have a certain surface finish quality. In manufacturing of thermoplastic composites using automated fiber placement (AFP) for aerodynamic applications, it is not only desirable to achieve good consolidation by using AFP alone and avoiding secondary treatment in an autoclave, but also to achieve acceptable surface smoothness required for aerosurfaces. In this study, an in situ treatment called “repass” was implemented to achieve surface finish quality required for aerodynamic applications. Moreover, the effect of this in situ treatment on the quality of the thermoplastic laminates, including void content and crystallinity was investigated. Autoclave-treated samples were used as references for comparing surface quality and other quality indicators.