Fiber reinforced composites full elastic characterization with surface longitudinal waves, using ultrasonic laser...

Area of Science:

• Materials Science
• Mechanical Engineering
• Non-Destructive Testing

Background:

• Conventional elastic characterization of composites is complex, often requiring multiple samples and intricate setups.
• Anisotropic materials, common in composites, pose significant challenges for traditional elastic property determination.
• Existing ultrasonic and mechanical methods can be time-consuming and sample-intensive.

Purpose of the Study:

• To develop and validate a non-destructive, laser-based methodology for comprehensive elastic characterization of fiber-reinforced composites.
• To overcome the limitations of conventional techniques in determining the elasticity matrix, especially for anisotropic materials.
• To enable precise measurement of elastic properties from a single specimen.

Main Methods:

• Utilized surface skimming longitudinal waves (SSLW) generated by an ultrasonic probe and detected via laser interferometry.
• Employed a laser-based approach for precise group velocity measurements across a 180° angular sector of a single specimen.
• Applied a polar scanning scheme with B-scan and high-resolution time-of-flight analysis to extract SSLW velocities.
• Used an inverse optimization algorithm based on Christoffel equations to retrieve elastic constants from experimental velocities.

Main Results:

• The laser-based methodology was successfully validated on isotropic PMMA and applied to transversely isotropic composites.
• Accurate extraction of SSLW velocities was achieved, showing strong agreement with contact-mode ultrasonic measurements and theoretical models.
• Four out of five independent elastic constants were successfully retrieved for the tested composites.
• The method accurately estimated the principal anisotropy direction in a composite with unknown fiber orientation.

Conclusions:

• The proposed laser interferometry technique offers a robust and versatile non-destructive method for comprehensive elastic characterization of composite materials.
• This approach simplifies the process, requiring only a single specimen and avoiding complex configurations.
• The methodology is effective for both isotropic and anisotropic composites, including those with unknown fiber orientations.