Detailed non-destructive evaluation of UHMWPE composites in the terahertz range

Abstract

We report on the terahertz analysis of an internal structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material, which is based on the HB10-tape from Dyneema . This type of composite is very hard and resistant and therefore it is often used to manufacture personal armors such as bulletproof vests and helmets. The multilayer structure of the UHMWPE composite was investigated by means of a raster scanning time domain spectroscopy technique in a reflection configuration. The mechanism of the formation of many shifted in time THz pulses (reflected from the internal layers of the sample) originates from the periodic modulation of the refractive index along the propagation of the radiation. This modulation is connected with alternate layers of fibers, each having different direction (perpendicular to each other). As a result we obtained the detailed three dimensional profile of the 3.3-mm thick sample with all 74 layers clearly visible. Thicknesses of all layers, having around 45 µm each, were determined. Moreover, it is also possible to identify internal defects i.e. delaminations in the internal structure of this composite material.

Precise Determination of Thicknesses of Multilayer Polyethylene Composite Materials by Terahertz Time-Domain Spectroscopy

“…1b), and the interleaving period is about 100 mm. The thickness of a single ply was about 40-50 μm [13] as measured with a micrometer screw as well as with a microscope. The arrangement of plies inside an HB10 tape in this process is random, and due to its woven nature, there are regions with regular (0°-90°-0°-90°) and irregular (90°-0°-0°-90°) sequence of layers (Fig.…”

“…The determination of thicknesses of their layers, investigating delaminations and other defects, is crucial for reliable characterization of the manufacturing process and quality control. Up to now, the UHMWPE composites have not been intensely studied in the THz range [12,13]. The non-destructive evaluation of composite materials [1][2][3][14][15][16] was mostly carried out by the use of THz time-domain spectroscopy (TDS).…”

“…Because of the multilayered structure of composite materials, a sequence of pulses shifted in time is observed each pulse coming from a reflection from a particular interface. Generally, knowing the refractive index of the single layer, we can determine its thickness on the basis of the time difference between two pulses (their peaks) reflected from the front and back surfaces of this layer [13]. However, for thin layers, roughly about 50 μm, pulses reflected from adjacent layers overlap and cause errors in determining thicknesses of consecutive layers.…”

Spectroscopic study of terahertz reflection and transmission properties of carbon-fiber-reinforced plastic composites

“…1,2 In the past two decades, THz science and technology have been developed tremendously due to impressive improvements of ultrafast optoelectronics and low-dimensional semiconductor technology. The applications of THz technology have been extended to security, 3 pharmaceutical sciences, 4 nondestructive evaluation (NDE), 5,6 and many others. Carbon-fiberreinforced plastic (CFRP) laminates are useful composite materials.…”

Pulsed excitation terahertz tomography – multiparametric approach

“…Trays are sensitive to complex permittivity changes, therefore any defect or structure detail causing its noticeable disturbance can be detected. The most common method of defects localization is transmission or reflection imaging based on pulsed terahertz Time Domain Spectroscopy (THz TDS) [1][2][3][4][5].…”