Terahertz imaging and tomography as efficient instruments for testing polymer additive manufacturing objects

Abstract

Additive manufacturing (AM) technology is not only used to make 3D objects but also for rapid prototyping. In industry and laboratories, quality controls for these objects are necessary though difficult to implement compared to classical methods of fabrication because the layer-by-layer printing allows for very complex object manufacturing that is unachievable with standard tools. Furthermore, AM can induce unknown or unexpected defects. Consequently, we demonstrate terahertz (THz) imaging as an innovative method for 2D inspection of polymer materials. Moreover, THz tomography may be considered as an alternative to x-ray tomography and cheaper 3D imaging for routine control. This paper proposes an experimental study of 3D polymer objects obtained by additive manufacturing techniques. This approach allows us to characterize defects and to control dimensions by volumetric measurements on 3D data reconstructed by tomography.

Hyperspectral Terahertz Tomography in Amplitude Contrast

“…The profile model shows enhanced edge attenuation because of high reflectance at near grazing incidence. The contribution of surface roughness is more prominent at smaller σ, in agreement with (8).…”

“…Examples of THz tomography imaging have been reported to date using THz pulsed [1,[6][7][8], or continuous wave (CW) sources [1,[9][10][11]. Results achieved by time-of-flight or phase contrast with pulsed sources are the most convincing yet.…”

Dielectric Losses of Paper in the THz Domain: Literature Review, Needs for Future Research, and Prospective Solutions

“…Chitosan produced from sea shell chitin has been proposed to flocculate and retain fine particles in papermaking: it also features high dielectric losses . Bio‐based plastics such as polylactic acid (PLA) has intrinsic losses similar to paper . Olefin based plastics indeed have low losses but may not be compatible with cellulosic fibres, not to mention environmental issues.…”

“…Bio‐based plastics such as polylactic acid (PLA) has intrinsic losses similar to paper . Olefin based plastics indeed have low losses but may not be compatible with cellulosic fibres, not to mention environmental issues. Mineral oil possess very low loss factor, but causes toxicity problems in food contact applications, and contaminates the whole recovered paper chain upon recycling .…”

Review of GaN-based devices for terahertz operation

“…15 THz-TDS systems are powerful tools for material spectroscopy, layer inspection, and transmission imaging of packaged objects. 16 These capabilities of THz-TDS systems are utilized in authentication, [17][18][19] nondestructive inspection of composite materials, [20][21][22][23][24][25][26][27][28] threedimensional imaging, [29][30][31][32] metrology and quality control of industrial products, [33][34][35][36][37] detection of concealed weapons, [38][39][40][41][42][43][44][45] art investigations, 46,47 tomography, [48][49][50][51][52] biomedical diagnosis, [53][54][55][56] material characterization, [57][58][59][60][61][62] thickness measurement, …”