Finite Element Modeling of Plates with Arbitrary Oriented Isogrid Stiffeners

Abstract

The main focus of this paper is the study of grid stiffened plates. The plates are modeled using the finite element approach. A 2D 8-node plate element is proposed. The advantage of the proposed element is that it can model plates with stiffeners within the element. This can yield models with many fewer elements for grid structures. A parametric study is presented to study the effect of the stiffener angle on the element stiffness in an attempt to optimize the stiffener configuration. For validation purposes, three cases are considered; plain plate, plate with straight stiffeners, and plate with isogrid stiffeners. The modal frequencies and modes of the plates are calculated using the proposed model and compared with the predictions of the commercial finite element package ANSYS® as well as experimental measurements taken on three plates manufactured by stereo lithography technique. The comparisons demonstrate the validity of the proposed model and the effectiveness of the isogrid stiffeners compared to straight stiffeners of the same mass in significantly increasing the fundamental frequency. The obtained results emphasize the potential of employing isogrid stiffeners in numerous vibration and noise control applications.

Keywords:

• isogrid stiffener
• grid structures
• stiffeners
• finite element
• plates

ACKNOWLEDGMENT

This work is funded by the Office of Naval Research (Grant number N000140610074). Special thanks are due to Dr. Kam Ng, the technical monitor, for his invaluable inputs.