Experimental Investigation on Bullet Proof Materials: (FRP, UHMWPE, ARAMID, Al2O3 and SiC)

Experimental Investigation on Bullet Proof Materials: (FRP, UHMWPE, ARAMID, Al2O3 and SiC)

Gangu Vardhan

Mechanical Engineering

NRI Institute of Technology, Vijayawada, India

Oleti Uday Kumar

Mechanical Engineering

NRI Institute of Technology, Vijayawada, India

Chinthakayala Teja

Mechanical Engineering

NRI Institute of Technology, Vijayawada, India

Dr. K BabuRaja Associate Professor Mechanical Engineering

NRI Institute of Technology, Vijayawada, India

Abstract This project analyzes the hardness behavior of selected materials for bulletproof applications., namely fibre- reinforced polymer (FRP), ultra-high-molecular-weight polyethylene (UHMWPE), aramid composite, alumina (AlO), and silicon carbide (SiC). These materials are commonly used in bullet proof materials and vehicle armor systems due to their distinct mechanical characteristics. Polymer-based armor layers such as FRP, UHMWPE, and aramid laminates are evaluated using the Shore D hardness test, which is suitable for assessing relatively softer composite materials. In contrast, ceramic materials like alumina and silicon carbide are examined using Rockwell and Brinell hardness tests to account for their extremely high stiffness and brittle nature. The study aims to measure and compare the hardness values of each material, analyze the influence of material composition and microstructure on hardness, and correlate these properties with reported ballistic performance parameters such as energy absorption and penetration resistance. Based on the results, suitable combinations of polymer and ceramic materials are identified for developing lightweight hybrid bullet-resistant panels, providing useful design data for future armor applications.

Keywords Bulletproof composite, Bulletproof standard, Fabric structure, Hardness of materials, Shore D hardness test and Rockwell hardness test.

1. Introduction : Bulletproof materials, or ballistic materials, are specially engineered substances designed to protect personnel and vehicles from high-velocity projectiles like bullets and shrapnel. Historically evolving from silk and steel to advanced polymers, modern ballistic armor operates by absorbing and dissipating the kinetic energy of an impact, preventing penetration while minimizing injury. Soft armor stops projectiles by "catching" and mushrooming them, distributing force over a wide area, while hard armor plates shatter or deform high-caliber rifle rounds on impact. Modern, lightweight, high-performance vests often combine both, offering crucial protection to military and law enforcement personnel with improved mobility and reduced weight. The need for advanced personnel protection against ballistic threats has driven significant innovations in material science, moving from early metal plating to sophisticated composites. Modern "bulletproof" materialsmore accurately termed bullet- resistantare designed to catch, deform, and dissipate the kinetic energy of a projectile, preventing it from penetrating the textile or hard matrix.This study will compare the

   efficiency of these materials, evaluating parameters such as tensile strength, weight-to-strength ratio, and energy absorption capabilities, as no single material is optimal for all threats. Through experimental testingsimulating bullet impact on layered compositesthe project aims to determine the optimal thickness and material composition required to achieve high ballistic resistance while minimizing weight and maximizing comfort for the user. By examining the deformation and penetration mechanisms under controlled conditions, this research will contribute to identifying superior materials and design configurations for modern body armor applications.

2. METHODOLOGY:

   OBJECTIVES OF THE STUDY:

   • Evaluate the ballistic resistance of FRP composites against high-velocity projectiles to assess energy absorption and penetration prevention.

   • Investigate the performance of UHMWPE fabrics in terms of tensile strength, lightweight design, and deformation under bullet impact.

   • Analyze the protective capabilities of aramid fibers, focusing on their abrasion resistance and multi-hit performance in experimental setups.

   • Compare the hardness and fracture toughness of Al2O3 ceramics as hard strike faces for disrupting bullet cores during impact.

   • Determine the effectiveness of SiC ceramics in eroding projectiles and maintaining structural integrity under repeated ballistic testing.

     SELECTION OF BULLET PROOF MATERIALS:

     Rising demand for lightweight, high-performance body armor and vehicle protection amid global security threats makes ballistic materials research timely and impactful. These specific materials represent a balanced mix of soft (FRP, UHMWPE, aramid) and hard (Al2O3, SiC) options, allowing comprehensive hybrid system testing.

   • Relevance and Innovation: Addresses NIJ standards for multi-hit resistance while exploring cost-effective alternatives to traditional steel, ideal for India's defence manufacturing.

   • Feasibility: Materials like UHMWPE and aramid are commercially available; Al2O3/SiC ceramics enable lab-scale ballistic testing with standard firearms.

   • Academic Value: Fills gaps in comparative studies on FRP-ceramic hybrids, offering publishable data on failure modes and optimization.

     MATERIALS SELECTION:

     FRP: Selected as a lightweight backing material to support ceramic layers and absorb residual impact energy.

     UHMWPE: Chosen for its very high tensile strength, low density, and excellent energy absorption capability.

     Aramid: Used for flexible armor due to high toughness, impact resistance, and shock dissipation.

     AlO: Selected as a cost-effective ceramic to fracture and blunt the projectile on impact.

     SiC: Chosen for superior hardness, lower weight, and excellent ballistic performance.

3. EXPERIMENTATION:

   UMMWPE SAMPLE:

   • Ultra-High Molecular Weight Polyethylene (UHMWPE) fabric samples were prepared to study their mechanical performance and hardness characteristics and to enable comparison with aramid (Kevlar) composite samples. UHMWPE was selected due to its low density, high strength- to-weight ratio, and excellent energy absorption capability.

   • The UHMWPE fabric sheets were initially cut to the required dimensions of 210 mm × 150 mm using precision cutting tool and the cut sample shown in below figure. Each individual UHMWPE layer had an approximate weight of 8 g. To achieve the desired thickness and mass, a total of 53 fabric layers were stacked, resulting in an overall sample weight of 395 g .

   • Before stacking, the UHMWPE fabric layers were visually inspected and cleaned to remove surface dust and loose contaminants.Only dry cleaning and careful handling were employed to avoid fiber damage.UHMWPE sample coverd with a polythene cover shown in figure 1.

     Figure 1: Uhmwpe sample coverd with a polythene cover

   • The cleaned UHMWPE layers were then carefully aligned and stacked uniformly to ensure consistent thickness and load distribution. After stacking, the layered fabric assembly was compressed and trimmed to obtain uniform

     edges. The consolidated UHMWPEstack was then subjected to controlled pressing to improve interlayer contact and reduce void content.

   • Following trimming and consolidation, the final sample thickness was measured and found to be approximately 14 mm. The sample was allowed to stabilize at ambient laboratory conditions to avoid dimensional changes due to temperature or humidity variations. The completed sample is covered with a polyster cover and shown in below figure.

   • After stabilization, the prepared UHMWPE composite sample was protected from environmental exposure and subsequently sent for hardness testing and mechanical characterization.

     UHMWPE Fabric Sample Specifications:

   • Length: 210 mm

   • Width: 150 mm

   • Single layer weight: 8 g

   • Total number of layers: 53

   • Total weight: 395 g

   • Final thickness (after trimming): 14 mm

   • Surface area: 31,500 mm²

   • Volume: 441,000 mm³

   • Areal density: 0.0125 g/mm²

   • Volumetric density: 8.956 × 10 g/mm³ FRP SAMPLE:

   • The present study involves the fabrication of a Fiber Reinforced Polymer (FRP) composite using woven fiber fabric and a polymer resin system. The reinforcing fabric used is a plain-woven fiber fabric with an individual fiber thickness of approximately 0.1 mm. The fabric has an areal density (GSM) of about 305 g/m².

   • The FRP composite is manufactured using epoxy polyester resin as the matrix material, along with a suitable hardener and catalyst. The primary objective of this work is to prepare an FRP laminate and evaluate its hardness characteristics, followed by comparison with other materials. Hardner and catalyst mixing process shown in figure 2.

     Figure 2: Hardner and catalyst mixing process

   • The fiber fabric is first cut to the required dimensions. A total of 35 layers of the fabric is stacked to obtain the desired laminate thickness. The resin system is prepared by taking epoxypolyester resin equal to 30% of the total weight of the fiber fabric. The hardener and catalyst are added in a ratio of 1:1 by weight with respect to the resin. All three components are thoroughly mixed using a mechanical stirrer to ensure uniformity.

   • The prepared resin mixture is uniformly applied to both sides of each fabric layer. The impregnated layers are stacked one over the other and properly aligned. After stacking, the laminate is subjected to compression using a hydraulic press operating at a pressure of 100 tons. This pressing process helps in removing entrapped air bubbles and ensures proper resin impregnation and bonding between layers.

   • The laminate is maintained under pressure for 12 hours to allow complete curing of the resin. After curing, the FRP laminate is removed from the press and cut to the required shape and dimensions. The prepared samples are protected from environmental and climatic effects before testing.

   • The final FRP specimen has dimensions of 210 mm × 150 mm with a thickness of 6 mm. The calculated area of the sample is 31,500 mm², and the volume is 189,000 mm³. The density of the fabricated FRP composite is approximately

     2.089 × 10³ g/mm³.

     • The prepared samples are then sent for hardness testing. KEVLAR (ARAMID) SAMPLE:

     • Aramid (Kevlar) fabric samples were prepared for evaluating mechanical hardness and energy absorption characteristics. Kevlar fibers were selected due to their high tensile strength, low density, and excellent impact resistance, making them suitable for protective applications such as ballistic pads.

     • The Kevlar fabric was manufactured using plain weaving, with individual fiber thickness of approximately 0.10

       mm. The areal density of the aramid fabric ranged from 60 GSM for lightweight applications up to 460 GSM or higher for heavy-duty use. In the present study, Kevlar fabric sheets were used to fabricate a multilayer composite pad Kevlar fabric shown in figure 3.

       Figure 3: Kevlar sample after stacking 27 fabric layers

     • Initially, the Kevlar fabric was cut into the required dimensions using precision fabric cutting tools. A total of 27 fabric layers were stacked to obtain the desired thickness and structural integrity. Each single layer had an approximate

       weight of 15 g, resulting in a total sample weight of 395 g. Fabric cutting process shown in figure 4.

       Fig No: 4 Fabric cutting process

     • Before stacking, the aramid fibers were cleaned to

       remove surface impurities. The fabric layers were treated by refluxing in acetone and ethanol for 48 hours, ensuring the removal of contaminants that could affect bonding and mechanical performance.

     • After cleaning, the fabric layers were aligned and stacked uniformly. The stacked layers were tied securely using a rope arrangement and placed inside a vacuum removal machine to eliminate entrapped air bubbles between the layers. This vacuum process enhances interlayer bonding and improves mechanical strength and energy absorption capacity.

     • The stacked Kevlar fabric was then subjected to hot pressing using a hydraulic press operating at 100-ton pressure. The hydraulic press machine shown in figure 5. During pressing, the temperature was maintained at 120°C using heaters to ensure proper consolidation. The sample was kept under constant pressure for 12 hours to complete the curing

       Figure 5: Hydraulic press machine

     • After curing, the consolidated sample was removed from the press and trimmed to the required dimensions. The sample was then protected from environmental and climatic conditions before further testing. Finally, the prepared Kevlar (aramid) composite sample was sent for hardness testing and other mechanical evaluations.

       Kevlar (Aramid) Fabric Sample Specifications\

     • Length: 210 mm

     • Width: 150 mm

     • Thickness: 10 mm

     • Total number of layers: 27

     • Total weight: 395 g

     • Surface area: 31,500 mm²

     • Volume: 315,000 mm³

     • Density of Kevlar fabric: 1.253 × 10³ g/mm³

     ALUMINIUM OXIDE (AlO) SAMPLE:

     High-purity aluminium oxide (AlO) powder was used as the base material for the preparation of bullet-proof ceramic samples. The powder was uniformly mixed with a small amount of organic binder to improve green strength and then dried to remove moisture. The dried powder was Subsequently; the samples were sintered at high temperature to achieve high density and hardness. After sintering, the specimens were machined and polished to the desired dimensions.

     Simple Sample Preparation Process for Aluminium Oxide:

     Powder Selection Mixing Oven Drying Drying Compaction Binder Removal Finishing Bonding

     1. Powder Selection: High-purity aluminium oxide powder is taken as the raw material.

     2. Mixing: The powder is mixed with a small amount of binder (such as PVA) and water or alcohol to get a uniform mixture.

     3. Drying: The mixed slurry is dried in an oven to remove moisture.

     4. Compaction: The dried powder is pressed into the required shape (tile or disc) using a hydraulic press.

     5. BinderRemoval: The pressed sample is slowly heated to remove the binder.

     6. Finishing: The sintered sample is polished or machined to the required size.

     7. Bonding: For ballistic testing, the ceramic tile is bonded to a backing material like Kevlar or UHMWPE

        Alumina (AlO) Ceramic Tile Density Calculation:

        • Shape: Regular hexagon Side length, s=19 mm

        • Thickness (height), h=9mm

        • Mass, m=20g

        • A=937.90mm^2

        • V=8441.1mm^3

        • =3.55×103g/mm^3

          Silicon carbide (SiC) SAMPLE:

          Silicon carbide specimens are first cut to the required dimensions using a diamond saw to avoid cracking due to its high hardness. The cut samples are then mounted (cold mounting preferred) for ease of handling. Sequential grinding is carried out using silicon carbide or diamond abrasive papers under continuous water cooling. This is followed by polishing with diamond paste to obtain a smooth, scratch-free surface. After polishing, the samples are ultrasonically cleaned in ethanol or distilled water and dried before testing.

          Sample preparation process for a Silicon carbide specimen.

          Silica + Carbon Ball Milling Pressure Reactor Argon Gas Environment Reaction Silicon Carbide (SiC) Silicon carbide sample calculations:

        • Shape: Regular hexagon

        • Side length,s=19 mm

        • Thickness (height), h=8 mm

        • Mass, m=20g

        • A=937.90mm2

        • =2.665×103

4. RESULT AND DISCUSSION:

   UHMWPE SPECIMEN:

   The Shore-D hardness values of 85, 85, and 90, with an average of 86.67, indicate that UHMWPE exhibits high and consistent surface hardness. The minimal variation between impressions reflects uniform material behavior. This hardness level confirms UHMWPEs good resistance to indentation and wear, making it suitable for energy-absorbing and protective applications in composite armor systems. Results are shown in below table.

   Table 1: Uhmwpe Shore D Hardness Results

   Impression No.	Shore-D Hardness
   Impression 1	85
   Impression 2	85
   Impression 3	90
   average	86.67

   Graph for the Uhmwpe specimen:

   The graph illustrates the Shore-D hardness values of the UHMWPE specimen for three impressions. Hardness values remain nearly constant at 85 for the first two impressions, with a slight increase to 90 in the third. The average hardness of

   86.67 indicates good surface hardness and repeatability. This consistent behavior confirms UHMWPEs suitability for energy absorption and wear resistance in composite armor applications.The UHMWPE result graph shown in graph 1.

   Graph No: 01 UHMWPE Result graph FRP SPECIMEN:

   The FRP specimen exhibited high Shore-D hardness values ranging from 84 to 85, with an average hardness of

   Impression no	Shore-D hardness
   Impression 1	82
   Impression 2	82
   Impression 3	83
   Average	82.33

   84.67. This indicates good surface rigidity and resistance to indentation. Such hardness confirms that FRP is suitable for use as a supportive structural layer in composite and lightweight armor applications. Results are shown in below table.

   Table 2: Frp Shore D Hardness Result

   Impression no	Shore-D Hardness
   Impression 1	84
   Impression 2	85
   Impression 3	85
   average	84.67

   Graph for the Frp specimen:

   The graph presents the Shore-D hardness values of the FRP specimen for three impressions. The hardness remains within a narrow range of 8485, resulting in an average value of 84.67. This minimal variation indicates uniform material quality and good surface rigidity. The observed hardness confirms FRPs ability to resist indentation, making it suitable as a supportive structural layer in lightweight and composite armor systems Related graph as shown in graph 2.

   Graph for the KEVLAR specimen:

   The graph illustrates Shore-D hardness values of 82, 82, and 83 for the Kevlar specimen, giving an average of 82.33. The minimal variation across impressions indicates uniform material behavior and reliable test results. When combined

   with its high tensile strength, Kevlar is well suited for energy- absorbing layers in protective composite systems Related shown in graph

   Graph No: 02 Frp Result graph KEVLAR SPECIMEN:

   The Kevlar specimen showed consistent Shore-D hardness values between 82 and 83, with an average of 82.33. This uniform hardness reflects stable material behavior and good resistance to surface deformation. Although slightly lower than FRP, Kevlars hardness, combined with its high tensile strength, makes it effective for energy absorption in protective composite systems as shown in table 3.

   Graph No:03 Kevlar Result graph ALUMINIUM OXIDE SPECIMEN:

   The aluminium oxide (AlO) specimen exhibited very high Rockwell hardness values ranging from 75 to 77 HRC, with an average of 76.33 HRC. Aluminium oxide (AlO) specimen results shown in below table. This confirms its excellent resistance to indentation and wear. Such high hardness makes alumina highly suitable for use as a ceramic strike-face material in ballistic and armor applications as shown in table 4.

   Impression No	Shore-D hardness
   Impression 1	75
   Impression 2	75
   Impression 3	77
   Average	76.33

   Table 4: Aluminium Oxide Hardness Results

   Graph for the Aluminium Oxide specimen:

   The graph shows Rockwell hardness values of 75, 75, and 77 for aluminium oxide (AlO) across three impressions, with an average of 76.33. The nearly flat trend indicates excellent consistency and repeatability of the measurements. Such high and stable hardness confirms aluminas strong resistance to surface indentation and wear, supporting its suitability for ceramic armor and protective applications as shown in graph 4.

   Graph 5: Silicon carbide Result graph

   DISCUSSIONS:

   Graph 4: Aluminium Oxide Result graph

   SILICON CARBIDE (SIC) SPECIMEN:

   The silicon carbide (SiC) specimen demonstrated extremely high Rockwell C hardness values between 85 and 87 HRC, with an average of 86.00 HRC. Compared to other tested materials, SiC shows superior hardness, making it highly effective as a front-layer ceramic for high-performance ballistic and armor apply Silicon carbide results are shown in table 5.

   Table 5: silicon carbide hardness results

   Impression No	Shore-D hardness
   Impression 1	85
   Impression 2	86
   Impression 3	87
   Average	86

   Graph for the Silicon carbide specimen:

   The graph presents the Rockwell C hardness variation of the silicon carbide specimen across three impressions. Hardness increases steadily from 85 to 87 HRC, inicating consistent and uniform mechanical behavior. The high average value of 86 HRC confirms silicon carbides exceptional resistance to indentation and penetration, supporting its suitability as a front-layer ceramic material for high-performance ballistic and armor applications. Related shown in graph 5.

   • All tested materials showed consistent hardness values with minimal variation, indicating uniform material properties and reliable Shore-D and Rockwell hardness testing results.

   • Polymer and composite materials (UHMWPE, FRP, and Kevlar) exhibited good surface hardness, making them suitable for energy absorption and structural support in composite armor systems.

   • Ceramic materials (AlO and SiC) demonstrated significantly higher hardness, confirming excellent resistance to indentation and penetration, which is essential for strike- face armor applications.

   • Among all specimens, silicon carbide showed the highest hardness, indicating that a multilayer armor system combining ceramic strike faces with composite backing layers provides optimal ballistic protection.

5. CONCLUSION

The present experimental investigation evaluated the hardness of UHMWPE, FRP, Kevlar, Aluminium Oxide (AlO), and Silicon Carbide (SiC) to determine their suitability for ballistic and composite armor applications. Shore-D and Rockwell hardness tests were conducted, showing consistent and repeatable results.UHMWPE exhibited an average Shore-D hardness of 86.67, indicating good surface hardness and energy absorption. FRP showed 84.67, reflecting good rigidity and structural stability, while Kevlar recorded 82.33, offering effective energy absorption and impact load distribution due to its high tensile strength.Ceramic materials displayed higher hardness values. AlO recorded 76.33 HRC, showing strong resistance to wear and indentation, while SiC showed the highest hardness of 86 HRC, indicating excellent penetration resistance.These results demonstrate that multilayer composite armor systems combining ceramics with polymer and fiber layers provide improved ballistic protection.

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