▎ 摘　　要

In the present study, free vibration and stability analyses of fluid-conveyed sandwich pipe with porous core and graphene platelet reinforced composite in top and bottom layers of face sheets are investigated based on the Timoshenko beam theory. Using Hamilton's principle, the governing equations of motion are obtained based on the first variations approach. The differential quadrature method (DQM) is used to solve to solve these equations. The effect of volume fraction of porosity in four different relationships, including nonlinear, and exponential, on the natural frequency, stability, and specific weight of the sandwich pipe is studied. Also, three void shape factors of the porous core, including circle geometry, are assumed. Moreover, five famous and popular core materials covering Steel, Aluminum, Al2O3, Cast Iron, and Polyethylene are considered. The influence of fluid flow velocity inside the pipe as an essential parameter on vibration and stability of the structure is illustrated. Three types of composite face sheets, including graphene platelet (GPL), glass fiber (GF), and three-phase (GPL + GF) as well as polymer as matrix, are investigated. Graphene Platelet as reinforcement is added to Glass Fiber for reinforcing composites factsheet layer. This research can be used to manufacture oil and gas transmission and distribution pipelines and chemical processing plants with high stiffness. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.