Investigation of the Tensile, Flexural, and Impact Strengths of Hexagonal Expanded Aluminum Mesh/Biaxial Glass Fiber Hybrid Composites

Glass fibers are known for their high tensile strength, thermal properties, environmental resistance, and more. This research article investigates the mechanical properties of composites made of hexagonal expanded aluminum mesh (HEAM) of 1.03mm (0.04in) strand thickness, 6.5mm (0.25in) long way of opening (LWO), 5mm (0.2in) Short Way of Opening (SWO) and 1708 45/45 biaxial fiberglass with binder epoxy resin (LY556) with Hardener (HY918) with silicon dioxide as an additive. This study determines tensile, flexural, impact strengths. Results show hexagonal mesh efficiently distributes loads, yielding high strength-to-weight ratio, tensile strength, and energy absorption.


Introduction
The advent of technology has kept pace with the evolution of mankind.Tools were the first instruments that required materials.To build these tools, humans kept track of how each material performed.Whenever they found a new material that could replace an old one, they would test it out.This way, materials played a very important part in tool making.The earliest records of advanced materials can be traced to the end of the Stone Age, when practices like smelting and casting were introduced.Plywood was the first form of composite to be made.A composite material is made up of two or more distinct materials, each of which has their own unique features.Composite materials are created when diverse materials come together within a medium.This composite material exhibits a completely different property when compared individually.Therefore, it is crucial to study the various compositions of these advanced materials.
Reinforcement and matrix make up the two main parts of a composite material.The reinforcement provides the composite with its stiffness and strength.It enhances the composite's mechanical qualities.The primary function of the matrix is to act as a medium of load transfer between the layers of the reinforcement.It holds the reinforcement together.The matrix greatly influences the thermal, electrical, magnetic, and several other properties of the composite.
Reinforcements can be in the form of fibres and particles.Fibres are long, hairlike strands, whereas particles are very fine, like granules.The direction of fibre orientation plays a key role in the way forces are distributed throughout the composite when loaded.Matrices can be classified into polymer, metal, and ceramic bases.[20] Further composites can be classified based on their layers within.A laminate is made up of one or more planar layers.Here, each layer may be similar or dissimilar fibre and each layer is called a lamina or ply.Whereas a sandwich laminate is a form of composite where the core layer is sandwiched in between two face laminates.These sandwiched laminates have very high stiffness and strength.They are used in lightweight structural applications [10].
The composite we aim to study is designed as a sandwich laminate where the Hexagonal Expanded Aluminum Mesh (HEAM) is the core layer.A layer of chopped strand mat with random fibre orientation is layered on both sides of the core.Over these layers, another layer of chopped strand mat stitched with two successive layers of crosshatched biaxial glass fibres oriented at 45° to the normal are laid.A suitable matrix of LY556, HY918 with Silicon Dioxide as an additive has been materialised.

Experiment Details and Methodology
The ASTM D3039, ASTM D790, and ASTM D256 standards are used, respectively, to test the tensile strength, flexural strength, and impact strength of the manufactured composites.The dimensions of these standards are in Table 1

Materials
The materials used in this study were • Binder epoxy resin : Huntsman resin LY556 is used with Hardener HY918 • 5% Silicon Dioxide as an additive.[11] The use of 45/45 Biaxial Fiberglass determines the composite's strength to weight ratio The strength-to-weight ratio of 45/45 biaxial fibreglass compared to chopped strand mat is higher.Stitched biaxial fibreglass cloth provides added strength with less additional weight than thicker chopped strand mat.Compared to woven fabrics, biaxial fiberglass cloth is more stiff and requires less resin since it conforms quickly.This also means that there is less print-through.[14][13] Hexagonal Expanded Aluminium Mesh

Specimen Preparation
This hybrid composite is fabricated using the hand Lay-up method.[15][19] Releasing agentwax is applied to the specimen preparation surface [7].First, we place the biaxial glass fibre mat, followed by chopped strand mat, followed by HEAM followed by chopped strand mat, and finally biaxial glass fibre.With 2 wt% of silicon dioxide for each specimen.The weight percentage of the composite is represented in Table 1, which is based on optimum mixture design from a literature review [17]

Pretest Measurements
The below explains the necessary dimensions of the specimen according to their respective standards.

Tensile Test
A basic mechanical tensile test determines a material's capacity to bear tension or stretching forces before breaking.Tensile tests were performed on all five specimens using measurements from Table 2 and Figure 4 in compliance with ASTM D3039.The tensile tests were performed in a universal testing machine (UTM) UTN -20/6/79-235, at a constant cross-speed of approximately 1 mm/min, at room temperature of 28 °Celsius and relative humidity of 67% as shown in Fig 5 .The testing apparatus's vise was used to mount the standard specimen by its ends.And the specimen is subjected to the load until failure.Maximum forces are recorded and represented in Table 3.When the load is applied to an Ultimate Tensile strength, it will suddenly drop, which means the composite material breaks as a whole, Specimen 4 showed enhanced mechanical property, From Specimen 1 to 4 there is increase in Ultimate Tensile strength owing to decreasing weight percentage of epoxy.We see the highest ultimate strength in S5 because of the absence of metal mesh; the composite was completely made with glass fibres and epoxy, which resulted in their increased ultimate strength.The maximum load at this time is found to be 0.138 Mpa by Specimen 5.By varying the epoxy percentage, it was found that the 50-50% composite composition performed the best.Two types of failure are observed, for the specimens with mesh: the Angled Gage Top (AGT) type of failure mode and Angled Gage Middle (AGM) failure mode for the specimen without mesh.Specimens following failure are displayed in Figure 6.

Flexural Test
The composite material's flexural strength refers to its capacity to bear bending stresses that are applied perpendicular to its longitudinal axis.A material's flexural modulus can be used to determine how stiff it is.When the specimen is placed on a support span and the force is applied to the centre by the nose, three-point bending results.The test is conducted according to ASTM D790 using the Universal Testing Machine UTN 20/6/79-235 at 28°C and a relative  4.  8 and Figure 9 represents the Flexural testing of the specimen and its post flexural test images.It is observed that S4 has higher flexural strength properties.The maximum flexural strength of the composite is found to be 0.202 MPa at 35-55% weight ratio of the composite.

Impact Test
A single-point test called the Notched Izod Impact test gauges a material's ability to withstand impacts from a swinging pendulum and its notch sensitivity at high strain rates.The results of impact strength are expressed in Energy per unit thickness J/m at the notch [9].
The impact properties are furnished in Table 5.And Figure 11 represents the images post Impact testing.Incorporation of Mesh in the composite enhanced its ability to absorb shock loads.The impact tests conducted on the composite samples revealed that varying the epoxy content affected the material's impact resistance.Samples with an optimised percentage of epoxy displayed improved energy absorption and impact strength.This result suggests a direct relationship between the epoxy matrix and the material's ability to absorb and dissipate energy upon impact [5] .

Morphological Analysis
Scanning Electron Micrograph analysis demonstrates that the hexagonal mesh played a vital role in preventing crack propagation, distributing stress more uniformly across the composite.SEM images of Flexural sites.
It is found that adding 55% of glass fibre and 35% epoxy has performed well in the test and is concluded as followsOptimum Fiber Content: The 55% fibre content in the composite material resulted in the optimal amount for achieving the desired mechanical properties.Improved interfacial Bonding: The addition of chopped strand mat increased the interfacial bonding between the fibre and the matrix, and the hexagonal mesh resulted in improved mechanical properties.[6] Optimum Fibre Orientation: The mechanical response of 45/45 Biaxial shows better load distribution compared to fibreglass in 90° orientation.Using silicon as a reinforcement helped increase its hardness, thereby increasing its wear resistance property.

Conclusion
The results of this study indicate that the composite material with 55-35% of fibre and resin made of 1708 45/45 biaxial fibreglass, epoxy resin, and a hexagonal mesh structure with 2% silicon dioxide as an additive has enhanced mechanical properties compared to the other materials The hexagonal mesh structure is very efficient in distributing loads, giving the composite a high strength-to-weight ratio, high flexural strength, and more impact energy absorption.[16] In specimens with less than 60% epoxy, the composite tends to delaminate at a faster rate during the test The study indicates that the incorporation of Hexagonal Expanded Aluminum Mesh (HEAM) in combination with 45/45 biaxial fibreglass at 55% of Glass fibres and 35% epoxy resulted in increasing the tensile property to 0.0896 MPa , the flexural property to 0.202 MPa and 28J of impact energy absorption compared to the one without mesh in it.The honeycomblike structure of the hexagonal mesh provides minimal density while maintaining high out-ofplane strength, thus resulting in efficient load distribution and giving the composite a high strength-to-weight ratio, high flexural strength, more energy absorption and therefore providing structural stability.Adding silicon dioxide as a filler material results in enhancing durability and becoming more resistant to wear.On the other hand, increasing their heat resistance and thermal stability.These improved properties like enhanced strength, energy absorption and lightweight nature align with demanding requirements of the automotive and aerospace manufacturing industries [11].In Marine engineering these composites can be used for creation of hulls and structural components because of high tensile properties [18].Further research could explore fine tuning the configuration of the hexagonal mesh and introduction of additives to push the boundaries of composite materials.

Figure 12 and
Figure12and FIgure13shows the microscopic analysis of Tensile and flexural material post testing.The minute neck formation of the aluminium mesh is observed in tensile failure.[4][8]

Figure 12 .
Figure 12.SEM images of Tensile Fracture sites.
Fibreglass: 1708 45/45 biaxial fibre.Biaxial contains glass backed by chopped strand mat on one side for bonding Biaxial contains cloth stitched at +/-45 degrees • 1708 45/45 Bi axial Fibreglass contains chopped strand mat on one side for bonding.

Table 1 .
Weight percentage Of Composite.

Table 3 .
Tensile Results of Composites .

Table 4 .
Flexural Results of Composites .

Table 5 .
Impact Properties of the Composite .