National Science Foundation IndustryUniversity Cooperative Research Center IUCRC

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National Science Foundation Industry/University
Cooperative Research Center (I/UCRC) Failure
and Structural Health Monitoring of Composites
Site Director Principal Investigators
Prof. Rakesh K. Kapania Prof. Rakesh K. Kapania
rkapania_at_vt.edu rkapania_at_vt.edu Ph.
540-231-4881 Prof. Ron Moffitt rmoffitt_at_vt.ed
u
Virginia Tech, 08/07/2007
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Introduction

• Composites and adhesively bonded joints are being
  increasingly used in aerospace and automobile
  industry
• High strength to weight ratio, high stiffness to
  weight ratio, lower life-cycle cost, less stress
  concentration are advantages
• Disadvantages include vulnerability to impact
  load, lack of efficient techniques to visualize
  the damage done to the adhesive layer
• A potential challenge to the safety of the
  structure
• Failure assessment and health monitoring of
  composite structure is a feasible solution to the
  problem

Virginia Tech, 08/07/2007
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How Our Work is Different

• Related Works Elsewhere
• Reviews on impact response of composites are
  presented by Kapania and Raciti (1989) 1, Soden
  et al. (1998) 2, and Abrate (1998) 3, and
  Icardi (2007) 4
• Delamination, fiber/matrix debonding, matrix
  cracking etc. still demand the attention of the
  researchers.
• Ultrasonic technique, vibration based techniques,
  pulse thermography etc. are available techniques
  for health monitoring of adhesively bonded
  composites.
• Fiber optic sensors have become very popular for
  use in health monitoring of structures.

• Key Features of Our Work
• Development of an efficient computational scheme
  by taking the effects of matrix cracking ,
  delamination growth, week adhesive bonds etc.
  into account.
• Computational simulation of lamb wave propagation
  in composites.
• Development of an health monitoring system with
  wireless sensor network for complex structures.

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Virginia Tech, 08/07/2007
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Deliverable and Budget
Deliverables

• Computational model to simulate impact response
  of composites with adhesive bonds
• Computational model to simulate lamb wave
  propagation in complex composite structure
• Health monitoring system with wireless network
  and feature extraction algorithm.

• Budget
• One graduate student and some nominal funding for
  travel and supplies etc. (40K)

Virginia Tech, 08/07/2007
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Related Work Within The Center

• Development of comprehensive computational models
  to predict damage growth in adhesively bonded
  composite structures, using rate-independent and
  rate-dependent models in collaboration with ACC
• Development of algorithms to predict location,
  extent and type of damage using wavelets and
  neural networks using transient response
  (vibration based) and wave-propagation (Lamb
  waves)
• Structural health monitoring of radial tires
  using wireless sensors under a grant from NASA
  Langley Research Center

Virginia Tech, 08/07/2007
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Description of Research

• 1. Computational Modeling
• A general finite element technique will be
  implemented to study the impact response of
  adhesively bonded complex composite structures.
• Commercial codes such as LS-DYNA , ABAQUS will be
  used.
• Taking care of the effects of damage mode
  interaction between matrix micro cracking,
  delamination, weak bond between the adhesive and
  the adherent, weak adhesive layer, complete
  voids, disbond or porosity will be major areas of
  concern in the modeling.

Reaction forces and crack growth using a high
fidelity model
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Virginia Tech, 08/07/2007
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Description of Research

• 2. Feature Extraction
• Signals from each sensor can be decomposed into a
  range of frequency sub-bands using Wavelet Packet
  Transform and damage matrix can be formed for
  each sensor location.
• Using ANN feature discrimination can be done from
  the damage matrices.

Displacement magnitude in an undamaged (left) and
damaged aluminum plate (right, 50 reduction in
stiffness of a 2mmX2mm patch in a 400mmX140mm
plate) due to 325KHz sinusoidal pulse using Local
Interaction Simulation Approach (LISA). We employ
wavelets to decompose the signals and artificial
neural networks for feature extraction. Time of
arrival and the magnitude of reflection from
damage indicate the location and the extent of
the damage, respectively.
Virginia Tech, 08/07/2007
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Description of Research

• 3. Lamb Wave Simulation
• Local Interaction Simulation Approach (LISA),
  incorporating a Sharp Interface Model (SIM), is
  an efficient approach to simulate lamb wave
  propagation.
• We have employed LISA for full three dimensional
  problems 5 .

Displacement amplitude profiles determined using
3D LISA for an undamaged (left) and damaged
(right) aluminum cross stiffened plate at 30µs
due to a five cycle 300 kHz windowed pulse from
a surface mounted actuator modeled using
enforced displacement over the actuator
footprint
Virginia Tech, 08/07/2007
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Description of Research

• 4. Wireless Sensor Network
• Hardware will consist of crossbow motes, sensors
  and onboard computer.
• The mote set-up requires a transceiver
  (MPR410CB), a data logger (MDA300), and a base
  station (MIBB510)

Wireless Network Setup

• 5. Experimental Verification
• various developments on an adhesively-bonded
  example composite structure will be verified
  experimentally in the lab.

Virginia Tech, 08/07/2007
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Project Schedule
Virginia Tech, 08/07/2007
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References
1 Kapania, R.K., and Raciti, S., 1989,
Recent Advances in Analysis of Laminated
Beams and Plates, Part II Vibration and Wave
Propagation AIAA Journal , Vol. 27, pp.
935-949 2 Soden, P., Hinton, M., and
Kaddour, A. 1998 A comparison of the
predictive capabilities capabilities of current
failure theories for composite laminates,
Composites Science and Technology, 58, 12251254.
3 Abrate, S., 1998, Impact on Composite
Structures, Cambridge University Press,
Cambridge, U.K.
4 Icardi, U., 2007, C0 Plate Element Based on
Strain Energy Updating and Spline Interpolation,
for Analysis and Impact Damage in Laminated
Composites, International Journal of Impact
Engineering, Vol. 34, pp. 1835-1868.
5 Bland, S. M., and Kapania, R. K., Efficient
Three-Dimensional Simulation of Lamb Wave
Propagation in Damaged Stiffened Plates, ASCE,
Engineering Mechanics Division Conference,
Blacksburg, VA.
Virginia Tech, 08/07/2007