Elastic Properties of Glass & Glass-Ceramic by Resonance Testing (ASTM C623)

Introduction to Resonance Testing for Elastic Properties

Resonance testing — also called sonic resonance or impulse excitation technique (IET) — is a non-destructive method for determining the elastic properties of glass and glass-ceramic materials by measuring the natural resonant frequencies of test specimens. The elastic modulus, shear modulus, and Poisson’s ratio of the material are calculated from the specimen’s resonant frequencies, dimensions, and mass.

This technique applies to isotropic materials, including flat glass, optical glass, glass-ceramic substrates, technical ceramics, and composite glass panels. It is governed by ASTM C623 and ASTM C1259 for glass and advanced ceramics, respectively.

Why Resonance Testing Is Used for Glass and Glass-Ceramics

Glass and glass-ceramics are brittle materials that require non-destructive characterisation methods. Conventional tensile testing is impractical for glass because machining round tensile specimens without introducing surface damage is extremely difficult. Resonance testing requires only simple bar or disc specimens, can be performed quickly and non-destructively, and provides all three fundamental elastic constants (E, G, and ν) from a single test.

Additionally, resonance testing is highly repeatable (uncertainties <0.5%) and provides dynamic elastic modulus values relevant to high-frequency loading conditions encountered in acoustic, seismic, and vibration applications.

Principle of the Impulse Excitation Technique

The test specimen (typically a rectangular bar or disc) is placed on compliant supports at its nodal points and struck with a small impulse tool. The resulting vibration signal is captured by a microphone or accelerometer. Fast Fourier Transform (FFT) analysis of the transient signal identifies the resonant frequencies:

• Flexural (bending) resonant frequency → Young’s Modulus (E)
• Torsional resonant frequency → Shear Modulus (G)
• Poisson’s ratio (ν) is calculated from E and G

ASTM C623 specifies calculation procedures for flat glass and glass-ceramics; ASTM C1259 covers advanced ceramics.

Elastic Properties Determined

Young’s Modulus (E)

Young’s modulus (elastic modulus) describes the stiffness of the glass — its resistance to elastic deformation under tensile or compressive stress. For common soda-lime-silicate flat glass, E ≈ 70–74 GPa. Glass-ceramics (e.g., Zerodur, Macor) have E values from 65–95 GPa depending on crystalline phase content.

Shear Modulus (G)

Shear modulus describes resistance to shear deformation. For glass, G ≈ 29–31 GPa. It is critical for torsional stiffness calculations in structural glass beams and for acoustic vibration modelling.

Poisson’s Ratio (ν)

Poisson’s ratio relates lateral strain to axial strain. For silicate glass, ν ≈ 0.20–0.24. It is required for complete three-dimensional stress analysis and finite element modelling of glass structures.

High-Temperature Resonance Testing

ASTM C623 includes provisions for elevated temperature elastic modulus measurement using a furnace-equipped resonance test setup. High-temperature E data is essential for designing glass-to-metal seals, glass processing equipment, and glass-ceramic heat exchangers where thermal stresses depend critically on the elastic modulus at elevated temperatures.

Applications Across Industries

In architectural and structural glass engineering, elastic property data feeds into finite element analysis for glass beams, façades, and floor design. In the optical industry, glass substrate elastic properties are required for lens mounting stress calculations and mirror blank deflection analysis. In electronics, glass-ceramic substrates for microelectronic packaging are characterised for elastic properties to predict CTE mismatch stresses during assembly.

Conclusion

Resonance testing using the impulse excitation technique (IET) is a powerful, non-destructive method for accurately determining the elastic properties of glass and glass-ceramic materials. Analysing natural resonant frequencies enables precise calculation of Young’s modulus, shear modulus, and Poisson’s ratio without damaging the specimen. Its high repeatability, minimal specimen preparation, and ability to operate at elevated temperatures make it an essential tool for material characterisation, quality control, and advanced engineering design. Across industries such as architecture, electronics, and optics, resonance testing provides critical data for predicting structural performance, vibration behaviour, and thermal stress response in brittle materials.

Why Choose Infinita Lab for Resonance Testing of Glass and Glass-Ceramics?

Infinita Lab provides ASTM C623 and ASTM C1259 resonance testing for glass, glass-ceramics, and advanced ceramics through our nationwide accredited laboratory network. Our non-destructive testing specialists deliver accurate, reproducible elastic property measurements with rapid turnaround.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.

Frequently Asked Questions (FAQs)