umi-umd-2052

256 Pages·2004·1.5 MB·English

ABSTRACT
TitleofDissertation: DEVELOPMENT OF MACH SCALE ROTORS
WITH COMPOSITE TAILORED COUPLINGS
FOR VIBRATION REDUCTION
Jinsong Bao, Doctor of Philosophy, 2004
Dissertation directed by: Professor Inderjit Chopra
Department of Aerospace Engineering
The use of composite tailored couplings in rotor blades to reduce vibratory
hub loads was studied through design, structural and aeroelastic analysis, fab-
rication, and wind tunnel test of Mach scale articulated composite rotors with
tailored flap-bending/torsion couplings. The rotor design was nominally based
on the UH-60 BLACK HAWK rotor. The 6-foot diameter blades have a SC1095
profile and feature a linear twist of -12 deg. The analysis of composite rotor was
carried out using a mixed cross-section structural model, and UMARC.
Five sets of composite rotor were fabricated, including a baseline rotor with-
out coupling, rotors with spanwise uniform positive coupling and negative cou-
pling, and rotors with spanwise dual-segmented coupling (FBT-P/N) and triple-
segmented coupling. The blade composite D-spar is the primary structural el-
ement supporting the blade loads and providing the desired elastic couplings.
Non-rotating tests were performed to examine blade structural properties. The
measurements showed good correlation with predictions, and good repeatability
for the four blades of each rotor set.
All rotorswere tested at a rotorspeed of 2300rpm (tipMach number 0.65)at
different advanceratiosandthrust levels, intheGlennL.MartinWindTunnelat
the University of Maryland. The test results showed that flap-bending/torsion
couplings have a significant effect on the rotor vibratory hub loads. All cou-
pled rotors reduced the 4/rev vertical force for advance ratios up to 0.3, with
reductions ranging from 1 to 34%. The mixed coupling rotor FBT-P/N reduced
overall 4/rev hub loads at advance ratios of 0.1, 0.2 and 0.3. At a rotor speed of
2300 rpm and an advance ratio of 0.3, the FBT-P/N rotor achieved 15% reduc-
tion for 4/rev vertical force, 3% for 4/rev in-plane force and 14% for 4/rev head
moment. The reductions inthe4/rev hubloadsarerelated totheexperimentally
observed reductions in 3/rev and 5/rev blade flap bending moments.
Through the present research, it has been experimentally demonstrated that
structural couplings can significantly impact rotor vibration characteristics, and
with suitable design optimization (coupling strength and spanwise distribution)
they can be used to reduce vibratory hub loads without penalties.
DEVELOPMENT OF MACH SCALE ROTORS
WITH COMPOSITE TAILORED COUPLINGS
FOR VIBRATION REDUCTION
by
Jinsong Bao
Dissertation submitted to the Faculty of the Graduate School of the
University of Maryland, College Park in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
2004
Advisory Committee:
Professor Inderjit Chopra, Chair/Advisor
Associate Professor James Baeder
Professor Jian-Guo Liu, Dean’s Representative
Professor Darryll Pines
Professor Norman Wereley
(cid:13)c Copyright by
Jinsong Bao
2004
DEDICATION
to my parents, my wife, and my daughter
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ACKNOWLEDGEMENTS
I would like to express my deepest gratitude and appreciation to
my advisor, Dr. Inderjit Chopra. Without his invaluable guidance,
constant encouragement and support, this work would not be com-
pleted. I am also thankful to all members of my dissertation com-
mittee: Dr.James Baeder, Dr. Jian-Guo Liu, Dr. Darryll Pines and
Dr. Norman Wereley. Their comments, suggestions and constructive
criticisms have enriched my research. Also, I thank Dr. Anthony
Vizzini (current at Mississippi State University) for his suggestions
in the fabrication of composite models.
I would like to thank Dr.Andreas Bernhard (he is the program man-
ager of this project at Sikorsky Aircraft Corporation) for his invalu-
able technical support, countless feedbacks, and constructive com-
ments and suggestions for the years of this research. I would also like
to thank Dr.V. T. Nagaraj, not only for his generous technical sup-
ports over the course of this work, but for his sincere advice through
the sharing of his experience and technical expertise.
I would like to acknowledge the support provided by shared fund-
ing from the U.S. rotorcraft industry and government under the
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RITA/NASACooperative Agreement No.NCC2-9019, Advanced Ro-
torcraft Technology, 01 January 2001, with Technical Monitor Mr.
William Welsh from Sikorsky Aircraft Corporation.
I thank all my friends at the Alfred Gessow Rotorcraft Center for
their kind assistance and technical support. I have been benefited
from studying and working together, and sharing stories with my
colleagues. Especially, I would like to thank for the technical sup-
portsfromAnubhav Datta, Jayant Sirohi, MaoYang, Joshua Ellison,
Beatrice Roget, Jinwei Shen, Ben Berry and Mark Kimball. Thanks
as well to Bernie LaFrance at the Engineering Machine Shop, Matt
Fox at the Manufacturing Building and Les Yeh at the Wind Tunnel
for their technical supports.
I want to express my appreciations here for the moral support of my
many teachers and friends, especially from Prof. Shoushen Liu and
Prof. Xiaogu Zhang; Qiang Liu, Huaming Wang, and Hao Kang.
Above all, I would like to profoundly acknowledge my wife, Hong,
for her love, patience, and encouragement at all times. I would like
to express my deep gratitude for the love and support of my parents.
I thank my daughter, Yiwen, for her love and smile, and the joys
she gives us every day. Without their support and understanding, I
could not have completed this work.
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TABLE OF CONTENTS
List of Tables ix
List of Figures xi
1 Introduction 1
1.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background and Motivation . . . . . . . . . . . . . . . . . . . . . 2
1.3 Summary of Previous Work . . . . . . . . . . . . . . . . . . . . . 7
1.3.1 Structural Modeling of Composite Blade . . . . . . . . . . 7
1.3.2 Aeroelastic Analysis of Composite Rotor . . . . . . . . . . 8
1.3.3 Experimental Investigation of Composite Coupled Blade . 12
1.4 Scope of Present Research . . . . . . . . . . . . . . . . . . . . . . 16
1.5 Contributions of Present Research . . . . . . . . . . . . . . . . . . 20
1.6 Overview of Dissertation . . . . . . . . . . . . . . . . . . . . . . . 22
2 Composite Rotor Analytic Model 24
2.1 Composite Blade Cross-Section Structural Model . . . . . . . . . 25
2.1.1 Coordinate System and Basic Assumptions . . . . . . . . . 26
2.1.2 Laminate Analysis . . . . . . . . . . . . . . . . . . . . . . 26
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2.1.3 Displacement Model . . . . . . . . . . . . . . . . . . . . . 29
2.1.4 Mixed Force and Displacement Model . . . . . . . . . . . . 33
2.2 Composite Rotor Analysis . . . . . . . . . . . . . . . . . . . . . . 36
2.2.1 Equations of Motion . . . . . . . . . . . . . . . . . . . . . 36
2.2.2 Coupled Trim Analysis . . . . . . . . . . . . . . . . . . . . 39
3 Design of Mach Scale Composite Tailored Rotor 53
3.1 General Design Issues . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2 Full Scale Rotor Analysis . . . . . . . . . . . . . . . . . . . . . . . 55
3.2.1 Full Scale Rotors . . . . . . . . . . . . . . . . . . . . . . . 56
3.2.2 Effect of Couplings on Blade Frequency and Mode Shape . 57
3.2.3 Effect of Couplings on Vibratory Hub Loads . . . . . . . . 58
3.3 Parameters of Mach Scale Composite Tailored Rotor . . . . . . . 59
3.4 Structural Design of Mach Scale Composite Tailored Blade . . . . 61
3.4.1 Composite Material Selection . . . . . . . . . . . . . . . . 61
3.4.2 Measurement of Composite Mechanical Properties . . . . . 63
3.4.3 Structural Design of Composite Spar . . . . . . . . . . . . 65
3.4.4 Design of Composite Blade Root Insert . . . . . . . . . . . 67
3.4.5 Design of Leading-Edge Weight . . . . . . . . . . . . . . . 68
3.5 Layup Design of Composite D-spar . . . . . . . . . . . . . . . . . 69
4 Fabrication of Mach Scale Composite Tailored Rotor 104
4.1 Design of New Twisted Blade Mold . . . . . . . . . . . . . . . . . 104
4.2 Fabrication Process . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.2.1 Preparation of Foam Core . . . . . . . . . . . . . . . . . . 106
4.2.2 Preparation of Blade Layup . . . . . . . . . . . . . . . . . 108
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4.2.3 Layup of Composite D-spar . . . . . . . . . . . . . . . . . 109
4.2.4 Blade Curing and Finishing . . . . . . . . . . . . . . . . . 111
5 Experimental Examination of Blade Structural Properties 125
5.1 Bench-top Static Test . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.1.1 Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
5.1.2 Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . 127
5.2 Bench-top Shaker Test . . . . . . . . . . . . . . . . . . . . . . . . 129
5.3 Non-rotating Dynamic Test . . . . . . . . . . . . . . . . . . . . . 131
6 Wind Tunnel Test Results and Discussion 151
6.1 Test Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
6.1.1 Rotor Test Stand . . . . . . . . . . . . . . . . . . . . . . . 151
6.1.2 Wind Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.2 Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . 155
6.3.1 Overview of Test Data Quality . . . . . . . . . . . . . . . 155
6.3.2 Rotor Vibratory Hub Loads . . . . . . . . . . . . . . . . . 156
6.3.3 Blade Oscillatory Flap Bending Moment . . . . . . . . . . 162
6.4 Feasibility Study of Full Scale Composite Tailored Rotor . . . . . 164
7 Summaries and Conclusions 192
7.1 Composite Rotor Analysis . . . . . . . . . . . . . . . . . . . . . . 192
7.2 Mach Scale Composite Tailored Blade Design . . . . . . . . . . . 193
7.3 Mach Scale Composite Tailored Blade Fabrication . . . . . . . . . 195
7.4 Bench-top Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
7.5 Wind Tunnel Tests . . . . . . . . . . . . . . . . . . . . . . . . . . 196
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