Non-destructive determination of the density distribution of polymer foam models with THz-pulses

Abstract

A study of density and glue distributions in polymer foam models for lost foam casting processes is reported. THzpulse measurements were compared with destructive measurements according to the principle of buoyancy-floating method to guarantee high quality standards in lost foam casting processes.

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

“…Recently, many researchers reported that several polymer materials feature very low absorption and refractive index in the THz region (11,21). Thus, THz technology appears to be useful for characterizing dielectric material properties (23), superstructures (13), voids (22,31,41), inclusions (22,42), defects (22,25,27), glass transition (43), and material aging processes (11). Moreover, the wavelength of THz radiation is comparable to foam cell size (14,21) and additives or fillers (22,23).…”

“…In the construction sector, polymer foam plates are often glued together to form a single unit. Detection of glue lines or adhesive bonds between two or more elements is possible by the THz imaging due to the higher density of the adhesive layer (12,13). Furthermore, calculation of the complex refractive index as a function of frequency reveals the thickness of the adhesive layer.…”

“…THz beams have also been used for detection of the heat-induced damage in porous polymer pumice stone (44) due to the changes in dielectric properties, which decrease when the material is exposed to high temperatures. In addition to defects, properties such as material density (13,22) and IR radiation absorption on nanoadditives (22,30) can be probed by THz waves. Increased material density reduces thermal conductivity as well as transmission due to scattering and absorption effects, which can also be seen in THz transmission spectra.…”

“…More recently, research in the field of THz technology is also focusing on the exploration of building materials. There are some research studies focused on detecting and analyzing material thicknesses and density (12)(13)(14)(15)(16), water absorption (17)(18)(19), optical constants (20)(21)(22)(23)(24), voids and delaminations (18,22,25), inclusions (22), mechanical defects (26,27), material aging (11), weld joints and adhesion (12,18,28), as well as process control (29)(30)(31). A small number of literature references show that the construction and building industry lags behind other sectors in THz applications.…”

The perspectives and trends of THz technology in material research for future communication - a comprehensive review

“…Zhang et al [157] fabricated dielectric metal film waveguides at microwave G band and 4.3 THz by plating metal film and dielectric film inside polycarbonate tube in 2019, and experimentally measured that waveguide Terahertz techniques are helpful for superstructures [97], properties of dielectric material [104], voids [98,99,105], defects [98,100,101], inclusions [98,106], material aging processes [107], and glass transition [108]. In addition, the wavelength of terahertz radiation is suitable to the additive or filler [98,104] [119, [123][124][125] As for noncontact non-destructive test is terahertz wave detection, which is given to test film thickness and coating [123,126], evaluate multilayer coatings [111,123,127], plot thickness distributions [123], detect inhomogeneity and coating layer defects [116,123], monitor dry-wet conversion [123], and determine concentration or the chemical composition [128].…”