Ultrasonic Characterization of Composite Materials 13 th International Symposium on Nondestructive Characterization of Materials Le Mans, France May , 2013 B. Boro Djordjevic, Ph.D. Materials and Sensors Technologies, Inc. 798 Cromwell Park Drive, Suite C Glen Burnie, MD Phone: , Fax: , Copyright  Materials and Sensors Technologies, Inc, 2013

COMPOSITES HAVE A LONG HISTORY* *

Composites Copyright  Materials and Sensors Technologies, Inc, 2013

Composites Copyright  Materials and Sensors Technologies, Inc, 2013

Ultrasonic wave tests of composites require appropriate selection of transducers and signal processing. Adding composite material adds complexity to the test parameters. Copyright  Materials and Sensors Technologies, Inc, 2013 ASSUMPTION REALITY Ultrasonic Characterization of Composite Materials

Ultrasonic path in composite laminates senses the material’s directionality properties. In ultrasonic testing, the signal path is usually in Z direction of composite. Design of composites critical properties is usually in plane. Transmitter Receiver PATH Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Ultrasonic C-scan of Composite Honeycomb Using Water Jet System Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials Traditional ultrasonic testing of large composite structure Transmitter Receiver PATH In-thickness test

PIN and Miniature Transducers Sensing Transducer Performance, small vs large aperture vs wedge Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Nd:YAG pulsed Laser Data acquisition and signal processing Amplifier Formed laser source Test panel Laser or contact detector Guided wave source (Time 0 ) Traveling wave Test “Gage” Length Guided Wave Ultrasonic Test Setup Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials In-plane test

Copyright  Materials and Sensors Technologies, Inc, 2013 Guided wave Ultrasonic Signal Source Sub-Wavelength Probe 2 nd interface Long Range Ultrasonic Guided Waves in Composite Structures

Guided wave tests on difficult geometry require appropriate selection of transducers and signal processing. Guided waves reach zones that are not testable using conventional ultrasonic approaches. Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Elastic Modulus Measurement Source (Laser/Piezoelectric ) Receiver L S R L= Longitudinal S= Shear R= Rayleigh Homogeneous, Isotropic: 1 2 Homogeneous, Orthotropic (Plane Strain): Copyright  Materials and Sensors Technologies, Inc, 2013 Long Range Ultrasonic Guided Waves in Composite Structures Poisson’s Ratio

laser beam transducers 2 1 Transducer 2 Transducer 1 Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

14 Performance estimates for the guided wave composite characterization GAUGE PATH, FLAT SURFACE PATH ERROR TIME INTERVAL ΔT in μs DIGITIZER ERROR FIRST ARRIVAL PEAK ARRIVAL ZERO CROSSING mm + /- mm %ASSUMED V =10 mm/μs + / - 4ns+ / - 50 ns % + / - 20 ns % + / - 4 ns %20, %0.25 %0.10 %0.04 % %15, %0.33 %0.13 %0.053 % %10, %0.5 %0.20 %0.08 % %5, %1.0 %0.40 %0.16 % %2, %2.0 %0.80 %0.32 % Zero crossing most accurate Measurements capable of resolving changes as small as 1in10 3 to 1in10 4 Bi-static transmit/receive configuration Conventional methods cannot achieve such accuracy Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

15 FIRST PRINCIPLES TEST ASSUMPTIONS: SOUND VELOCITY V XY RELATES TO COMPOSITE DIRECTIONAL MODULUS VIA E XY =k x V 2 XY where k is specific materials constant Depending on “Guided Wave” modes, different material parameters control V XY. Copyright  Materials and Sensors Technologies, Inc, 2013 Absolute and Direct Sensing of the Composite Materials Elastic Modulus Materials Properties Measurements Ultrasonic Characterization of Composite Materials

Copyright  Materials and Sensors Technologies, Inc, 2013 Directional Ultrasonic Testing of Composites Ultrasonic Characterization of Composite Materials

Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Plot of samples velocity with measured modulus (Samples D to G) and samples without the known modulus values (Samples A, B and C) Samples A, B and C are same material but with different thickness and surface preparation Copyright  Materials and Sensors Technologies, Inc, 2003 A B CD E F G Direct Sensing of the Composite Materials Elastic Modulus Ultrasonic Characterization of Composite Materials

Guided wave testing of the Gr/E overwrap layer on COPV Ultrasonic configuration includes laser source and sub-wavelength sensors Copyright  Materials and Sensors Technologies, Inc, 2013 Testing Direction Ultrasonic Characterization of Composite Materials

GOOD MATERIAL SIGNAL DAMAGED MATERIAL SIGNAL High amplitude signal with discrete head wave used for time measurements Discrete guided wave modes at slower speeds No head wave signal Strong guided wave signal at low frequency Total local loss of fiber material modulus Cycled bottle signals 8 μs record 60 μs record Head wave Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Copyright  Materials and Sensors Technologies, Inc, 2013 Damage developing at the bottle diameter(radius) change with some broken fiber(tows) locations. Ultrasonic Characterization of Composite Materials

SUMMARY Guided Wave Ultrasonic Characterization of Advanced Composites Ultrasonic in-plane guided wave propagation is a complex process (especially in composites ) but it can enable in-plane material properties characterization. Ultrasonic transduction process is critical for validity and quality of the in-plane test measurements. A reproducible and robust laser-generation and sub-wavelength transducer sensing methodology/technology has been developed for the sensing of the materials properties. Laser ultrasonic guided waves tools enable one sided surface access measurements for the materials characterization. (Very useful) In-plane guided waves can measure mechanical modulus of the materials. Experimental tests confirm the utility of the methodology for the materials properties sensing. Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

APPLICATIONS SUMMARY:  Guided wave, advanced ultrasonic methods and custom sensors, in many test Configurations, including non- contact ultrasonic technology, are applicable for testing and materials properties characterization.  These methods are applicable for characterization of bond-lines, splices, composites(Gr/E, CC, metal-matrix..), structures (beams, complex assemblies..) layered and bonded sandwich structural components, in process applications (fiber placement, cure monitoring...), and for structural components integrity monitoring. Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

QUESTIONS B. Boro Djordjevic Phone: , Fax: , Copyright  Materials and Sensors Technologies, Inc, 2013

25 GENERAL DISPERSION CURVES FOR GUIDED PLATE WAVE IN A HOMOGENIOUS PLATE CALCULATIONS SHOW CONTINUOUS LINES, WAVES CAN EXIST ONLY AT DISCRETE LOCATIONS ON THE CURVE S0 mode Head wave A0 mode TEST ZONES Copyright  Materials and Sensors Technologies, Inc, 2013 Guided Waves Modes Ultrasonic Characterization of Composite Materials

Wavelet analysis of Lamb waveforms Single shot signal in a 1.6 mm Al plate Fourier transform Wavelet coefficients in the time-frequency plane Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

v = 1.7 mm/  s Test Results Carbon Fiber/Epoxy Amplitude (mV) Time (  sec) Defect-free Time (  sec) Amplitude (mV) Defect f = 0.8 MHz Lamb Wave Gr/E Composite Tests T R RT Line by line, (Gauge) test NOTE: Lower frequency test than traditional C-scan Point by point scan Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Nd:YAG Laser Data acquisition and signal processing Charge amplifier Lenticular array Test panel Air-coupled, laser or contact detector Large Area Guided Wave (Non-contact) Ultrasonic Test Setup Wave Source (Time 0 ) Traveling Wave Test “Gauge” Length Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Directional change of Velocity in unidirectional composite materials Copyright  Materials and Sensors Technologies, Inc, 2013 Direct Sensing of the Composite Materials Elastic Modulus Ultrasonic Characterization of Composite Materials

KEVLAR STRIP IN THE TENSILE LOAD FRAME Kevlar Composite UT Guided Wave Velocity Tests Plot of sound speed as function of strain for the two test runs. 1 in grips were used to hold 1 ½ in wide strip of Kevlar material. The overall strip length between grips was 38 cm. Ultrasonic guided wave test path was mm between laser source and receiving transducer roughly in the middle section of the sample. Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials

Copyright  Materials and Sensors Technologies, Inc, 2013 Ultrasonic Characterization of Composite Materials Kevlar Composite Overwrap UT Guided Wave Velocity Tests Scan Path

Velocity(modulus) change in the fatigued bottles. Bottle No 61 is considered a virgin sample. Copyright  Materials and Sensors Technologies, Inc, 2013 DAMAGE TESTING Ultrasonic Characterization of Composite Materials

33 General equation of wave motion, tensor notation:  ij /  x j =  ü i u=displacement  =mass density  ij =stress tensor Complexity due to directional properties Materials Properties Measurements Copyright  Materials and Sensors Technologies, Inc, 2003 Guided Wave Direct Sensing of the Composite Materials Elastic Modulus