NUMERICAL INVESTIGATION TO IDENTIFY MODAL PARAMETERS

CONSIDERING FIBER ORIENTATION OF FLEXIBLE COMPOSITE

WING

Eduardo Araujo

2014

der L. Oliveira*1, Roberto G. A. da Silva2, Adolfo G. Marto2, Eduardo F. R. de Araujo3

NUMERICAL INVESTIGATION TO IDENTIFY MODAL PARAMETERS

CONSIDERING FIBER ORIENTATION OF FLEXIBLE COMPOSITE WING

MODELS

1Instituto Tecnolgico de Aeronutica

eder@ita.br

2Instituto de Aeronutica e Espao

agmarto@iae.cta.br, gil@ita.br

3Engineering Scientific Simulation Software

eduardo.araujo@esss.com.br

INTRODUCTION

Introduction

Purposes of this work:

to understand the influence of different fiber orientations of thin composite

wing models on modal parameters.

to observe the influence of a piezoelectric (PZT) actuator in modal parameters

This work is related to intelligent structures, i.e., to have the ability to control

some displacements and stresses through some information collecting sensor

like PVDF films, and to actuate through PZT .

Introduction

Numerical Modal Analyses (NMA) is performed with ANSYS Workbench

5 simplified wing Models with different unidirectional carbon fiber orientation were modeled.

The model is a coupled model: Composite Structure modeled using ACP and later parametrized

1 PZT (Lead Zirconate Titanate) actuator

1 PVDF (Polyvinylidene Fluoride) sensor.

Introduction

Smart material influence observed

- structural damping

- local stiffness

- mass

Fiber orientation influence

- natural frequencies

- Vibration modes / twist vibration modes / flutter speed

Introduction

This work was verified through

experiments. See references [6] and [11].

Numerical Model Description

Numerical model

Numerical model

Figure 1. Composite wing model, dimensions and nominal orientation [6]

Numerical Model : Properties

Figure2: Numerical model and material properties

Initial Numerical Model (INM)

Classical Laminate Teory (CLT) INM

The INM creates using ANSYS uses the complete stress-strain relation.

Shear Moduli

Initial Numerical Model (INM)

Classical Laminate Theory (CLT) [6]

stress-strain relation in principal

material coordinates for a lamina

of an orthotropic material under

plane stress. Reduced stiffness

Engineering shear strain

Normal strain

Normal stress

Transverse shear stress

Check Step for Geometry and Meshing

Composite Modeling, Modal Analysis and

Harmonic Response with Electric Excitation

Numerical Model

Relevant Data

Composite wing model: SHELL181

Piezoelectric elements: SOLID226

Number of elements: 14300

Number of nodes: 20300

Mechanical loading values (displacements) due the difference of potential (Volts) imposed via

APDL.

Numerical Model

Coupling Matrix: T - stress D electric displacement S - strain E electric field

Permittivity

Piezoelectric constants

Stiffness matrix

Numerical Model

Difference of electric potential is converted in displacement and applied as harmonic effort.

APDL commands

cmsel,s,Ground_lower_surface_Piezo,node

d,all,volt,0

cmsel,s,Load_upper_surface_piezo,node

d,all,volt,17

allsel

Numerical Model Description

Results: Numerical model

Results - Numerical Model

Mode Shapes (Fiber Direction 0 degrees) are presented as reference

1st Mode Shape 2nd Mode Shape

3rd Mode Shape

Results NM and EM comparison

1st NM 1st EM 2nd EM 2nd NM

NM Numerical modes by Ansys EM - Experimental modes by [3]

Fiber direction 0 degrees

Results - Numerical Model

Model is parametric

Fiber direction may be a variable (Input)

Frequency Response Data may be Output for each variable

Results - Numerical Model

0,30,45,60 and 90 degrees were considered

Results for fiber direction 45 degrees are presented here

Results Experimental x Numerical Modal Analysis (45 degrees)

1st Mode Shape 2nd Mode Shape 3rd Mode Shape

Numerical

Experimental

Results - Numerical Model

Bode diagram: Amplitude X-Direction and Phase

Fiber direction 45 degrees

Results - Numerical Model

Bode diagram: Amplitude Y-Direction and Phase

Fiber direction 45 degrees

Results - Numerical Model

Bode diagram: Amplitude Z-Direction and Phase

Fiber direction 45 degrees

Results Experimental Model

Measurements were done using Vibrometer Laser and PVDF

One of objectives of this work was to validate the usage fo PVDF device as sensor

Image below shows the measurements obtained from the laser vibrometer and from the PVDF for the same experiment (same conditions) [11]

Note: Mobility (V/F)

Results - Numerical Model

Bode diagram: Velocity Z-Direction and Phase

Fiber direction 45 degrees

Conclusions

Coupled piezoeletric model available through Ansys r15

One may perform Modal and Harmonic Analysis

Results shows a good agreement between mode shape calculated numerically and the experimental ones

Results show that variations in the orientation have a significant influence on the stiffness, mode shapes and characteristic frequencies

Next work step is to compare these numerical results with experimental by EMA of the same flexible composite wing models, and to perform aeroelastic analyses using wind tunnel testing.

References

[1] C. E. de Souza, A. G. Marto, R. G. A. Silva, L. A. Inojosa, E. L. Oliveira, Characterization of Flexible Composite Wings Through Experimental and Operational Modal Analyses, DINAME 2013: Proceedings of the XV International Symposium on Dynamic Problems of

Mechanics, M.A. Savi (Editor) (2013).

[2] . L. Oliveira, A. G. Marto, R. G. A. da Silva, Thin Aeroelastic Wing Finite Element Model Updating with Experimental modal Analysis Results, Proceedings of COBEM 2011, 21st International Congress of Mechanical Engineering, October 24-28, 2011, Natal, RN,

Brazil.

[3] C. E. Prazzo, Anlise Modal de uma Estrutura do Tipo Viga Usando Materiais Piezeltricos (PVDF) Como Sensores (in portuguese), Dissertao de mestrado em Engenharia Mecnica - UNESP. Faculdade de Engenharia de Ilha Solteira., 2011.

[4] C. dos S. Guimares, Shape Control of Structures Using Piezoelectric Components, 2010, 109f. Trabalho de Concluso de Curso. (Graduao) ITA, So Jos dos Campos.

[5] ANSYS Mechanical APDL Technology Demonstration Guide, release 14.5 SAS IP, Inc Canonsburg ,nov 2011

[6] C. E. de Souza, Nonlinear Aeroelasticity of Composite Flat Plates, 2012, 170f. Thesis of Doctor in Science Technological Institute of Aeronautics, So Jos dos Campos.

References

[7] C. dos S. Guimares, F. L. de S. Bussamra, V. P. Bundiger, J. A. Hernandes, Structural Shape Control Using Macro Fiber Composite Piezoelectric Sensors and Actuators , Mecnica Computacional Vol XXIX, pgs. 8263-8279 (artculo completo) Eduardo Dvorkin, Marcela Goldschmit, Mario Storti (Eds.) Buenos Aires, Argentina, 15-18 Noviembre 2010.

[8] R. M. Jones, Mechanics of Composite Materials, 2nd ed. Washington: Scripta Book Co., 1999.

[9] J. Reddy, Mechanics of Laminated Composite Plates: theory and analysis, Boca Raton: CRC Press, 1997.

[10] D. J. Ewins, Modal Testing: theory and practice Letchworth: Reserch Studies Press Ltd, 1986.

[11] Oliveira, E.L. Application of Piezoeletric materials as sensor and actuator for aeroelastic investigation, Master of Science Thesis presented to Instituto Tecnologico de Aeronautica, So Jose dos Campos, Brasil, 2014

[12]Kostetzer, L. Piezoeletric Simulation with Ansys, ESSS, Florianpolis, Brasil, 2013

Acknowledgments