3D Non-destructive Imaging of Punctures in Polyethylene Composite Armor by THz Time Domain Spectroscopy

N Palka,F Ospald,R Panowicz,R Beigang

doi:10.1007/s10762-015-0174-4

Abstract

An ultra-high molecular weight polyethylene composite sample totally punctured by a projectile was examined by THz TDS raster scanning method in reflection configuration. The scanning results correctly match the distribution of delaminations inside the sample, which was proven with cross-sectional and frontal views after waterjet cutting. For further analysis, a signal-processing algorithm based on the deconvolution method was developed and the modified reference signal was used to reduce disturbances. The complex refractive index of the sample was determined by transmission TDS technique and was later used for the simulation of pulse propagation by the finite difference time domain method. These simulations verified the correctness of the proposed method and showed its constraints. Using the proposed algorithm, the ambiguous raw THz image was converted into a binary 3D image of the sample, which consists only of two areas: sample—polyethylene and delamination—air. As a result, a clear image of the distribution of delaminations with their spatial extent was obtained which can be used for further comparative analysis. The limitation of the proposed method is that parts of the central area of the puncture cannot be analyzed because tilted layers deflect the incident signal.

Highlights

Nowadays, newly developed composite materials introduce significant improvements in many domains of security including the protection of law enforcement and soldiers
We consider a ultra-high molecular weight polyethylene (UHMWPE) composite sample manufactured from HB26 material (Dyneema [2]) which was totally punctured by a 7.62-mm projectile from an AK-47 assault rifle (Kalashnikov)
The pulse reflected from the front surface of the sample is clearly seen, as well as the pulse corresponding to the back surface covered with the aluminum foil

Summary

Introduction

Newly developed composite materials introduce significant improvements in many domains of security including the protection of law enforcement and soldiers. The analyzed sample acts like a system of nets linked together, which can eventually stop the projectile Such progressive moderation of the velocity of the projectile results in bulges formed on the surface of the plate and causes internal delaminations occurring in the area close to the puncture. The spatial distribution of these delaminations and their position, range, direction, and width can be compared with the results of numerical simulations of the sample-projectile interaction which leads to better understanding of the underlying physical phenomena All these parameters allow for thorough investigation of this interaction and enable the determination of more details connected with the destruction of individual layers of the composite material and delaminations occurring between them. The detailed study of the underlying physical phenomena, in particular the process of destruction, is crucial for designing materials assuring higher ballistic protection

Methods

Results

Conclusion