Naresh Kakur

Recently, ceramics and metal-armed structures have been replaced by ceramics combined with ultra-high molecular weight polyethylene (UHMWPE) composite laminated structures for NIJ level III and level IV body armor applications. This shift is due to the superior specific energy absorption capabilities of the ceramics/UHMWPE composites compared to traditional ceramics and metal armor; however, it comes at a higher cost. Manufacturing body armor that offers higher specific energy absorption at a lower cost is challenging. As the thickness of UHMWPE increases, both the specific energy absorption and the overall cost of the body armor increase. Additionally, there is limited experimental data to evaluate the thickness of ceramics and UHMWPE to explore the performance of NIJ level III body armor, indicating that further research is needed. In this study, six different types of ballistic plate configurations were manufactured. Following that, high velocity impact tests were conducted to investigate the effects of front and back layer thicknesses of UHMWPE (Type 1 to Type 3 plates), the effects of foam material (Type 4 plate), and the effects of different thicknesses of boron carbide (B ₄ C) ceramic strike face (Type 5 and Type 6 plates) on the back face signature (BFS) of the ballistic plate. It was found that the BFS of Type 5 and Type 6 ballistic plate configurations is lower by 12% and 8.5%, respectively, compared with that of the Type 4 UHMWPE/polyvinyl chloride low-density foam ballistic plate. However, the Type 5 option is cost-effective and easy to manufacture, making it the preferred choice over the Type 6 variant.

Ultra-high molecular weight polyethylene (UHMWPE) laminate composites are widely used in impact-resistant structures due to their high specific strength and exceptional energy absorption capabilities. However, previous studies encountered challenges in characterizing the tensile properties of UHMWPE composites, including specimen slippage, stress concentrations, and failures outside the gauge length. This work presents the design and development of an interchangeable clamp for the tensile testing of UHMWPE composites. This clamp guarantees secure gripping and uniform load transfer across the UHMWPE specimens. The developed clamp can be used interchangeably in quasi-static and high-strain-rate devices, facilitating the evaluation of a broad range of strain rates. The tensile properties of two UHMWPE composites were subsequently assessed using this clamping system, with strain measured through three-dimensional digital image correlation (3D-DIC). The effectiveness of a 3D-DIC technique for measuring strain in the UHMWPE composite is demonstrated. The tests reveal that the designed clamp enables reliable measurements, with tensile strength values reaching approximately 1300 MPa. The measured tensile properties are useful for the input data of numerical simulations, providing valuable insights for developing highly efficient protective structures.