Title: Design of Ballistic Armor Using Multi-composite Sandwich Structures with Nanomaterial Additives

Authors: Carmen Alaichamy, Carlos Perez, Travis Murphy, Jack Bride, Eltahry Elghandour, Amro El Badawy

DOI:

Abstract: Ballistic armor is designed to withstand the impact of firearms and shrapnel. Current armor uses face layers of flexible materials, such as aramid fibers, combined with dense backing plates made of ceramics or metals to both stop bullets and minimize blunt-force trauma. These backing plates provide strong protection for the wearer but are often heavy, limiting mobility. To address these limitations, this study investigates composite sandwich structures as a lightweight alternative for ballistic protection applications. This work evaluates the ballistic performance of sandwich structures composed of woven Kevlar face sheets, polyurethane interlayers, and composite backing panels with varying fiber types, orientations, and thicknesses. Nanomaterial additives, such as graphene nanoplatelets, carbon nanotubes, and nanoclay, were explored as modifiers for the polyurethane interlayer to enhance energy absorption. Composite panels and polyurethane layers were fabricated and mechanically characterized prior to assembly into sandwich structures. Both individual composite panels and assembled sandwich structures were experimentally evaluated under 9mm hollow-point and fullmetal-jacket ballistic impact. Sandwich structures incorporating nanomaterial-modified polyurethane were also evaluated during ballistic testing; however, processing-related effects reduced mechanical integrity and ballistic effectiveness relative to unmodified polyurethane layers. Therefore, the most effective sandwich structures utilized unmodified polyurethane interlayers, thick, sewn Kevlar face sheets, and high-quality composite backing panels. The optimized configurations achieved penetration depths as low as 8% of the total sample thickness. These results highlight the importance of manufacturing quality and layer architecture in the design of composite sandwich structures for ballistic armor and provide guidance for future studies seeking to incorporate nanomaterials in ballistic applications.

References: Stereolithography (SLA)-printed polymers used in aerospace applications often require metallic coatings, commonly nickel. However, these coatings tend to fail at elevated temperatures due to mismatches in the coefficient of thermal expansion (CTE) between the polymer resin and the metal. This research aims to investigate the development and thermal characterization of hybrid multi-scale epoxy-based nanocomposites with reduced CTE to improve compatibility with nickel coating. A nanocomposite resin system was formulated using bisphenol A epoxy diacrylate (EBECRYL® 3700) as the base oligomer, trimethylolpropane triacrylate (TMPTA) as a reactive diluent, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and bis (2,4,6trimethylbenzoyl)-phenylphosphine oxide (BAPO) as photoinitiators. Nanosilica (25–55 wt%) and functionalized hexagonal boron nitride (h-BN, 0.5–2 wt%) were incorporated individually and as a multiscale hybrid reinforcement. Rheological behavior, thermomechanical properties, and thermal stability were systematically evaluated. All formulations exhibited shear-thinning behavior suitable for SLA processing. Thermomechanical analysis revealed a progressive reduction in CTE from 136.8 μm.m⁻¹ °C⁻¹ for the neat resin to a minimum of 103.2 μm.m⁻¹ °C⁻¹ for the hybrid system containing 55 wt% SiO₂ and 2 wt% h-BN. Differential scanning calorimetry showed moderate glass transition temperatures (38–57 °C) and a pronounced residual-cure exotherm between 60°C and 150°C, indicating incomplete photocuring and the need for post-curing. Thermogravimetric analysis demonstrated a single-step degradation at 440460 °C, with increased ceramic content increasing residual mass and enhancing high-temperature stability. The results establish clear processing–structure–property relationships and demonstrate that multiscale ceramic reinforcement is an effective strategy for producing dimensionally stable SLA resins suitable for nickel metallization and thermally demanding aerospace applications.

Conference: SAMPE 2026

Publication Date: 2026/04/27

SKU: 90

Pages: 15

Price: $30.00