An automated ultrasonic immersion technique for the determination of three-dimensional elastic constants of polymer composites

• Published in: Ultrasonics Vol. 36; no. 1; pp. 245 - 249
• Main Authors: Enderby, M.D., Clarke, A.R., Patel, M., Ogden, P., Johnson, A.A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.1998; Elsevier Science
• Subjects: Acoustical measurements and instrumentation; Acoustics; Applied sciences; Automated instrumentation; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Measurement and testing methods; Measurement methods and techniques in continuum mechanics of solids; Physics; Polymer composites; Polymer industry, paints, wood; Properties and testing; Solid mechanics; Structural and continuum mechanics; Technology of polymers; Testing and control; Three-dimensional elastic constants; Ultrasonic immersion technique; Polymer composites; Automated instrumentation; Three-dimensional elastic constants; Ultrasonic immersion technique; Elastic constant; Deformation modulus; Fiber reinforced material; Experimental study; Modeling; Composite material; Sound velocity; Immersion test; Three dimensional model; Automatic measurement; Time of flight method; Testing equipment; Measurement method; Ultrasound
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/S0041-624X(97)00065-6

An automated, ultrasonic immersion system based upon an original National Physics Laboratory design has been built and evaluated. Ultrasonic transducers operating at a frequency of 2.25 MHz have been used to investigate both tensile and shear velocities in fibre reinforced composite samples. The automation of the system allows fast and efficient large area scanning to be performed. Hence both large-scale, spatial variations in the tensile velocities can be investigated and also, all of the three-dimensional elastic moduli of fibre-reinforced polymer composites can be deduced by monitoring the variation of ultrasonic velocity with angle of incidence on orthogonal planes. Preliminary results indicate that the system will yield most of the three-dimensional elastic moduli to absolute accuracies of better than ± 1 % and in the fast scanning mode, will detect spatial variations of the time-of-flight of ultrasound with a fractional timing error of ± 0.001%. Work is in progress to correlate the ultrasonic propagation to three-dimensional mesostructural features. An automated, two-dimensional image analyser has been developed in-house and a Noran, three-dimensional confocal laser scanning microscope system is being automated at Leeds to determine the three-dimensional fibre orientation states and voidage within composite samples. Therefore it will soon be possible to evaluate existing models linking three-dimensional mesostructure to ultrasonic propagation and the stiffness constants of anisotropic materials.