What are the geometrical limits (thickness of the object, depth and size of defects, ..) for the shearography testing of composite materials (excepting honeycomb panels)?
Dear Vicktor
NDT Shearography is a surface inspection-technique, which can detect in-plane (tangential) defects in a scale of the 1/2 wavelength (as a spatial resolution,) of the laser light used in particular experiment.So, the thickness of the object is not relevant here.However, the depth and the size of defects should be not less than the spatial resolution of the laser light used in the experiment. For examble, if the
wavelength of the laser light used was 0.6 micrometer, for 10 mW HeNe laser light, the maximum spatial resolution one would get is 0.3 micrometer.
https://www.sciencedirect.com/search?qs=maximum%20defect%20depth%20that%20can%20be%20revealed%20by%20shearography%20NDT&show=25&sortBy=relevance
It is an interesting question and there are smart answers. I am wondering what if thermography NDT is?
Dear Kyungil
You can use shearography to develop thermography patterns of a later under heat condition,i.e., coated sample.Refer to the attachments:
Khaled J. Habib Thank you for your reply. I wondered what the maximum defect depth is revealed by thermography NDT...
Please see the references below:
1- G. De Angelis, M. Meo, D. P. Almond, S. G. Pickering, S. L. Angioni. A new technique to detect defect size and depth in composite structures using digital shearography and unconstrained optimization. NDT & E International, 45, (1), 91-96, 2012.
2- Y. Y. Hung, Y. S. Chen, S. P. Ng, L. Liu, P. S. Chung. Review and comparison of shearography and active thermography for nondestructive evaluation. Materials Science and Engineering: R: Reports, 64, (5-6), 73-112, 2009.
Best Regards
Dear Vicktor
the defect depth that can be revealed by shearography depends on the sensibility of the setup settled by the shearing distance and the kind of deffects you are interested in. So, for different experimets and different materials a flaw characterization neds to be done.
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