Study | Type of THz source | THz bandwidth | Range of time delay signal | Sample side dimensions | Sample scanning step size | THz system configuration mode | Refs. |
---|---|---|---|---|---|---|---|
Incident angle | Sample description | Type of defect (thickness) | Sample measuring methodology | Humidity levels | Scan method | ||
1 | Fiber-coupled PCA, pulsed THz-TDS | Information not provided | From 80 ps to 300 ps | 60 mm × 60 mm | 1 mm | THz system configured in reflection and transmission modes | [20] |
Information not provided | CFRP formed of 12 layers | Impact damage of unspecified thickness | Peak-to-peak and time-domain amplitude | Information not provided | Raster scanning of the CFRP composite samples | ||
2 | PCA, pulsed THz-TDS | Between 0.6–3 THz | From 0 ps to 45 ps | 50 mm × 50 mm | 0.1 mm | THz system configured in reflection and transmission modes | [13] |
Information not provided | GFRP formed of 8 layers | Teflon film (250 μm) | Time-domain amplitude | Information not provided | Raster scanning of the GFRP composite samples | ||
3 | PCA, pulsed THz-TDS | Between 0.1–4.5 THz | From 0 ps to 40 ps | 50 mm × 50 mm | 0.5 mm | THz system configured in reflection mode | [27] |
Information not provided | GFRP formed of 8 layers | Polytetrafluoroethylene (PTFE) films (205 µm) | Time-domain amplitude and time-of-flight tomography | Between 30%–32% | Raster scanning of the GFRP composite samples | ||
4 | PCA, pulsed THz-TDS | Between 0–3.5 THz | From 0 ps to 80 ps | 100 mm × 100 mm | Information not provided | THz system configured in reflection mode | [22] |
Information not provided | CFRP formed of 2 layers | Teflon film (150 μm) | Time-domain amplitude | Information not provided | Raster scanning of the CFRP composite samples | ||
5 | Fiber-coupled PCA, pulsed THz-TDS | Between 0.1–3 THz | From 26 ps to 48 ps | 30 mm × 30 mm | 1 mm | THz system configured in reflection mode | [26] |
Incidence angle set to \(25^\circ\) | GFRP formed of 12 layers of glass fabrics | Simulated delamination defects (100 μm) | Time-domain amplitude | Information not provided | Raster scanning of the GFRP composite samples | ||
6 | Fiber-coupled PCA, pulsed THz-TDS | Between 0–2 THz | From 0 ps to 100 ps | 22 mm × 44 mm | 0.2 mm | THz system configured in reflection mode | [25] |
N/A | A paper stack formed of 9 layers | Text (20 μm) | Time-gated spectral and time-domain amplitude | Information not provided | Raster scanning of the paper stack samples | ||
7 | Fiber-coupled PCA, pulsed THz-TDS | Between 0.1–4 THz | From 0 ps to 80 ps | 150 mm × 150 mm | 0.2 mm | THz system configured in the transmission and reflection modes | [24] |
Reflection mode (\(43.2^\circ\)) and normal transmission | GFRP formed of 4 layers of glass fabrics | Teflon film (100 μm, and 150 μm) | THz time and frequency-domain amplitudes, and the peak time shift algorithms | Between 46%–51 % | Raster scanning of the GFRP composite samples |