Optimization Studies of Kevlar/Epoxy Composites Strengthened with Hybrid SiC-ZnO Nanofillers using Taguchi L16 Technique

Abstract

Fibre Reinforced Polymer Composites (FRPCs) have been found to exhibit enhanced mechanical properties on addition of nanofillers. Recent research has also delved into the use of hybrid nanofillers to synergistically enhance their mechanical properties. In this present research, an attempt has been made to study the effect of hybrid Silicon Carbide (SiC) – Zinc Oxide (ZnO) nanofillers on the mechanical properties of Kevlar/Epoxy composite. Taguchi L16 technique has been employed in this current research for design and optimisation. The mechanical properties such as tensile strength, flexural strength, inter laminar shear strength and energy absorbed have been evaluated as output characteristics for optimising the input variables like weight percentage of SiC, weight percentage of ZnO, curing temperature and curing time. Confirmatory tests have also been performed for repeatability and validity.

Introduction

Fibre Reinforced Polymer Composites (FRPCs) are engineered materials combining strong reinforcing fibres with a polymer matrix, offering lightweight, high strength, stiffness, and corrosion resistance, making them ideal for aerospace, automotive, marine, and civil engineering applications. The addition of nanofillers further enhances mechanical and thermal performance by improving fibre–matrix adhesion, tensile strength, stiffness, fatigue resistance, thermal stability, and reducing moisture uptake.

1. Literature Review on Nanofiller Reinforcement

• Silicon Carbide (SiC) nanoparticles: Increased tensile strength in epoxy/glass fibre composites; performance improved with higher weight percentages (0–3 wt%).

• Nano silica: Enhanced tensile modulus, ultimate load, and mechanical properties in GFRP composites.

• Silica nanoparticles in different FRPCs (epoxy-basalt, epoxy-carbon, vinyl ester-basalt): Improved fracture toughness, particularly in epoxy-based composites.

• Nanoclay and ZnO in CFRP: Optimal wear resistance at 2–3 wt.% of each nanofiller.

• Nano-TiO? in jute/epoxy composites: 3 wt.% TiO? improved inter-laminar shear strength and reduced wear and friction.

• Silane-coated SiO? in glass FRP: Improved hardness significantly.

Hybrid nanofillers (combining two or more types) show synergistic effects, leading to:

• Superior fibre–matrix bonding

• Increased mechanical strength, toughness, and fatigue resistance

• Enhanced performance in aerospace, automotive, and structural composites

Examples of hybrid systems:

• Multi-walled carbon nanotubes + graphene: improved stiffness and fracture resistance

• Silica + cobalt ferrite: enhanced mechanical properties in glass/epoxy laminates

• Graphene oxide + nano silica in basalt fibre composites: improved tensile, flexural, impact strength, and hardness

2. Current Study: Kevlar/Epoxy Composites with Hybrid SiC-ZnO

Objective: Evaluate and optimize mechanical properties (tensile, flexural, inter-laminar shear strength, energy absorption) of Kevlar/Epoxy composites with hybrid SiC-ZnO nanofillers using Taguchi L16 design of experiments.

A. Materials Used

• Reinforcement: Kevlar Fibre Fabric Mat (8 layers, 220 g/m², 0.32 mm thickness, 12 µm filament diameter)

• Matrix: Epoxy resin LY556 + hardener HY951

• Hybrid Nanofillers: SiC (30–50 nm, 99.9%) and ZnO (30–50 nm, 99%)

B. Process Parameters for Optimization

• Wt.% of SiC: 0.5–1.25

• Wt.% of ZnO: 1–1.75

• Curing Temperature: 95–110 °C

• Curing Time: 55–70 mins

16 experiments were designed using Taguchi L16 array to identify optimal conditions.

3. Fabrication Method: Vacuum Bag Moulding

Process steps:

1. Cut Kevlar mats (30 × 30 cm)

2. Mix epoxy resin, hardener, and nanoparticles

3. Hand layup of eight Kevlar layers with nanoparticle-resin mixture

4. Cover with peel ply, vacuum bag film, and breather fabric

5. Apply vacuum for 3 hours to ensure uniform pressure, minimize voids, and improve fibre consolidation

6. Cure for 24 hours and remove specimens

Advantages of vacuum bagging:

• Better fibre consolidation

• Reduced porosity

• Improved resin distribution

• Enhanced surface finish

• Increased mechanical strength and durability

4. Key Insights

• Hybrid nanofillers improve mechanical properties of FRPCs more effectively than single fillers.

• SiC offers hardness, wear resistance, corrosion and radiation resistance

• ZnO provides high elastic modulus, strength, hardness, and fracture toughness

• Optimized process parameters (filler weight %, curing temperature, curing time) are crucial for achieving maximum performance

• Vacuum bag moulding ensures consistent quality and enhanced structural reliability

This study provides a systematic approach to design, fabricate, and optimize Kevlar/Epoxy hybrid nanocomposites, making them suitable for aerospace, automotive, and other high-performance structural applications.

Conclusion

The specimens were fabricated as per the Taguchi L16 experimental plan and were evaluated for mechanical properties such as tensile strength, flexural strength, inter laminar shear strength and energy absorption. ANOVA was employed to find the parameters influencing each mechanical property. Optimization studies were conducted to predict the optimal maximized specimens for each test. Finally, confirmatory tests were carried out for repeatability and validity of the experimental design. ANOVA revealed that weight percentage of SiC nanofiller was the parameter most influencing the tensile strength and flexural strength of the specimens, whereas weight percentage of ZnO nanofiller was the parameter most influencing the inter laminar shear strength and energy absorption. It can be concluded from the ANOVA studies that the use of hybrid nanofillers has led to synergistic enhancement of mechanical properties of the fabricated specimens. Optimization studies predicted that for maximum tensile strength and maximum flexural strength, the parametric condition was A2B2C1D2 (0.75 weight percent of SiC, 1.25 weight percent of ZnO, curing temperature of 950C and curing time of 60 minutes). Optimization studies predicted that for maximum inter laminar shear strength, the parametric condition was A3B2C1D2 (1 weight percent of SiC, 1.25 weight percent of ZnO, curing temperature of 950C and curing time of 60 minutes). Optimization studies predicted that for maximum energy absorption, the parametric condition was A3B4C3D3 (1 weight percent of SiC, 1.75 weight percent of ZnO, curing temperature of 1050C and curing time of 65 minutes). Confirmatory tests were conducted for repeatability and validation of the experimental model and it was observed that the predicted value and experimental values were in good agreement with each other. It can be concluded that the addition of SiC and ZnO nanofillers play an important role in enhancing mechanical properties of hybrid nanofilled FRPC.

References

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Copyright

Copyright © 2026 Bupesh Kumar K, B M Rajaprakash. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.