TITLE:

Measuring Crack Density in Composite Laminates using Piezoelectric Sensors

DATE:

Friday, October 18th, 2013

TIME:

3:30 PM

LOCATION:

GMCS 214

SPEAKER:

Dr. Cecilia Larrosa. Exponent Inc.

ABSTRACT:

The use of fiber reinforced composite materials has increased tremendously in many

applications from aerospace structures to sporting goods. These materials have many advantages,

but the major challenge in composites design is their damage mechanics. Matrix cracking

develops first, decreasing structural performance and promoting other damage development.

The state-of-the-art inspection techniques cannot quantify crack density and they require the

component to be off-service. For better design, safety, and maintenance of composite structures

it is desirable to monitor the increase of cracks in-service.

The objective of this investigation is to determine the quantity of matrix cracks in a

composite laminate rapidly and in-service using built-in piezoelectric actuators and sensors. A

diagnostic method was proposed which compared the sensed signal before and after the presence

of matrix cracks and related these signal changes to crack density. It was found that change in

the signal’s Power Spectral Density can be used to quantify crack density, and its sensitivity was

dependent on the actuator to sensor orientation. This orientation dependence was found to be the

same as that of the laminate’s stiffness degradation. A crack density monitoring method was

developed that uses signal changes and theoretical laminate stiffness degradation. The model was

tested on two layup configurations, and its crack density estimates matched experimental crack

density values within established error bounds.

HOST:

Dr. Satchi Venkataraman

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