A high speed camera for assessing structural integrity of composite materials through light scattering
Abstract
Publicly Releasable Project Summary and Abstract ONR Directorate: Airfame Structures and Materials ONR Program Manager: Bill C. Nickerson An optical image of the amplitude and polarization of scattered light is determined locally by surface texture and inclination. When a material is mechanically excited, the changing surface tilt and translation alter the image. Measurements made with high dynamic range and very low noise are sensitive to subtle surface changes. Tilts of the order of a microradian, and translations less than one micrometer can be discerned in spatially resolved ambient light passive scattering. Global analysis of a sequence through time of such measurements across a scene reveal the quantitative character of propagation of shock fronts, slow surface waves and interference, resonances, modal patterns, and damping. These response phenomena depend on material properties, not only on the surface but at depth, and thus provide information on material structural integrity. A combination of rapid excitation, low-noise imaging, and analysis tools are used to evaluate the quality of composite bonds and to assess effects due to aging, stress, impacts or heat. While mechanical responses at frequencies below 100 Hz are readily detected with state of the art machine vision silicon cameras, a much richer regime at frequencies up to 10,000 Hz has until recently been technically out of reach. Recent developments in low-noise CMOS image sensors, now available in the latest generation of high speed cameras, offer access to this domain where the effects of bond quality and material integrity are expected to appear prominently. We are developing a quantitative probe of composite bonds by moving an excitation source and using this optical technology to measure surface motion changes, thus providing rapid nondestructive testing of composite material quality over wide areas.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2017
- Source ID
- N000141712024
Entities
People
- John Kielkopf
Organizations
- Office of Naval Research
- United States Navy
- University of Louisville