Voids, thermography

Therefore, the condition D/d = 2 is a critical value, above which the thermography is applicable to detect the delamination or air voids in the C/SiC composite panel. More importantly, the errors in diameter measurement decrease with the increase of D/d and within the detectable range of D/d >2, the errors in depth measurement seem to decrease with depth increase. 

In composite materials, flaws, bonding faults and internal defects have all been examined using liquid crystal thermography, [177-184]. Surface and subsurface flaws have been detected, including regions of unstable plastic flow in aluminum alloys (Lueder lines) [185], faults in welded metals [186], and cracks, voids and leaks in pressure vessels [187-188]. Potential fracture sites have been determined in metals... 

Delamination, voids, and other hidden defects Impact echo, infrared thermography, pulse echo, and radar... 

Cracks, voids, and other discontinuities inside the mass are detected by nondestructive methods, such those of ultrasonic sonometer, radar, and IR thermography before and after the grout hardening (Tomazevic 1992). A draft assessment of achieved filling is made by this way. 

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