In the present study, two goniometry based immersion techniques have been compared for the measurement of elastic constants in isotropic and transversely isotropic materials. Measurements were carried out on transversely isotropic unidirectional (glass-epoxy and graphite-epoxy) composite materials. From the measured velocity data, the elastic constants were determined through a numerical inversion. These techniques (through-transmission and back-reflection) were verified using contact testing, mechanical testing, rule of mixtures estimation and the data provided by the manufacturers. The results obtained and the limitations of each of these techniques are discussed. © 2004 Elsevier Ltd. All rights reserved.

Krishnan Balasubramaniam

Department of Mechanical Engineering

C V Krishnamurthy

Department Of Physics

S. Siva Shashidhara Reddy

Epoxy resins

Graphite

Mechanical testing

Numerical methods

Velocity measurement

GLASS-EPOXY

IMMERSION TECHNIQUES

Isotropic materials

MIXTURES ESTIMATION

Composite materials

Elastic modulus

FIBER REINFORCED COMPOSITE

Testing

Ultrasonics

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Composite Structures

The reconstruction of all nine unknown elastic moduli of orthotropic plate structures has been achieved using a single-transmitter-multiple-receiver (STMR) compact structural health monitoring (SHM) array. This method uses the velocity measurement of the fundamental guided Lamb wave modes (S0 and A 0), generated from a central transmitter, and received by a sparse array of receivers that encircle the transmitter. The measured velocities are then used in an inversion algorithm based on genetic algorithms. A prototype compact STMR array was developed and used in the measurement. Simulated data were used to demonstrate the feasibility of the technique. Experiments were conducted on 3.15 mm graphite-epoxy composite plate using a PZT based STMR array as well as laser vibrometer based displacement measurement. Experimental Lamb wave velocity data were used to validate the present technique. This technique finds application in the areas of material characterization and SHM of anisotropic plate-like structures used in aerospace and automobile components made using fiber reinforced composites. © IOP Publishing Ltd.

Smart Materials and Structures

Genetic algorithm based reconstruction of the elastic moduli of orthotropic plates using an ultrasonic guided wave single-transmitter-multiple-receiver SHM array

Ultrasonic wave propagation provides a method for Nondestructive Characterisation of the clastic constants of materials. Goniometry based ultrasonic measurements were conducted in through transmission mode for isotropic and anisotropic materials using a conventional ultrasonic immersion transducer as a transmitter and a large aperture sensor made from Polyvinylidene Fluoride (PVDF) as receiver. The experimental results using this probe configuration were found to give improved transmission spectra that provides improved corroboration with the theoretical predictions based on Plane Wave Stiffness-Matrix based transmission factor model. Inversion of the clastic constants of materials, from the measured ultrasonic transmission spectra, was evaluated using two methods: (a) Genetic Algorithm and (b) Targeted Reconstruction. The inversions were carried out on transmission spectra obtained from both isotropic (Aluminum) and anisotropic materials (fiber reinforced graphite epoxy). The effectiveness of the large aperture receiver was also demonstrated from the results from inversion of the measured transmission spectra. © 2006 American Institute of Physics.

AIP Conference Proceedings

Elastic constants inversion from ultrasonic transmission spectra obtained using a wide aperture PVDF sensor

Journal of Testing and Evaluation

Ultrasonic Measurement of the Dynamic Elastic Moduli of Small Metal Samples

Review of Progress in Quantitative Nondestructive Evaluation

Measurement of Anisotropic Elastic Constants of an Aluminum Composite Plate Using a Double Reflection Method

The Ultrasonic Measurement of Elastic Constants of Structural FRP Composites

Genetic Algorithms for Inversion of Ultrasonic Data for the Elastic Constants Measurement in Orthotropic Material Systems

NDT & E International

Ultrasonic through-transmission characterization of thick fibre-reinforced composites

Ultrasonic goniometry immersion techniques for the measurement of elastic moduli

Journal	Composite Structures
ISSN	02638223
Open Access	No