Stacking Sequence and Weight Fraction Effect on Tensile and Flexural Properties of Woven Jute and Woven Carbon-Jute Reinforced Polyester Composites

Hybrid composites are a category of composites in which more than one types of fiber are used to reinforce the matrix. In this work, the mechanical properties of jute woven & and carbon-jute woven reinforced polymer matrix hybrid composites were evaluated to assess a comparative study between the two configurations varying the stacking sequences. Specimens of composites were prepared by hand layup process. To observe the effect of fiber weight fraction on properties, two types of composites were made having matrix-fiber weight fractions of 85:15 & and 80:20. Moreover, by altering the stacking sequences of the composites, these properties were also examined for the carbon-jute reinforced polymer matrix composites. It was observed that a hybrid jute-carbon composite having a stacking sequence of j/c/j/c/j and weight fraction ratio of 80:20 exhibited a better tensile strength of 108.795(10.885) MPa and Young’s modulus of 6.052(0.489) GPa. Superior flexural strength of 150.41 (±7.501) MPa and flexural modulus of 6.845(±0.825) GPA were found in hybrid jute-carbon composite having stacking sequence of j/c/j/c/j/c/j/c/j that has a weight fraction ratio of 80:20. In both cases, better mechanical properties were found for hybrid composites with higher fiber content and having alternate stacking sequences.


Introduction and Research Background
Composites are made up of two or more constituents that are incorporated in such a manner that each component can still be identified.Matrix and reinforcing fiber are the two main components.There are often just two components in a composite.In this case, one is the matrix or resin-wrapping and cementing the reinforcement's strands or shards into one cohesive unit.In recent years, natural fibers have attracted a great deal of attention due to the detrimental effects of manmade fibers on the environment.Scientists and researchers have taken notice of natural fibers due to their impressive benefits and the fact that they provide irrefutable evidence that high-performance materials may be derived from renewable sources with the help of green reinforcing options.1305 (2024) 012024 IOP Publishing doi:10.1088/1757-899X/1305/1/012024 2 Substituting traditional synthetic fibers with natural fibers to reinforce polymer matrix composites has the potential to pave the way for environmentally friendly and sustainable applications [1,2].Plant fibers are widely employed in diverse industries, particularly in composites, and they are generally grouped into three main categories based on their origin: Plant, Animal, or Mineral fibers.Lately, there has been a notable surge in the utilization of plant fibers to strengthen plastics in the composite manufacturing sector.Plant fibers are derived from various plant sources and offer several advantages when used in composite materials.Some of the most commonly used plant fibers in the industry are Cotton, Kapok, Flax, Hemp, Jute, Ramie, Sisal, etc. [3].Natural fibers present several advantages as reinforcements in composites [4].They are lightweight, resulting in composite materials with high specific properties.Additionally, natural fibers offer cost benefits and are easier to work with compared to synthetic fibers like glass, nylon, or carbon.However, the mechanical properties of composites made with natural fibers are not as strong as those reinforced with synthetic fibers.Furthermore, their limited resistance to moisture absorption is another drawback that may reduce their appeal for certain uses.Using synthetic fiber along with natural fiber can make the composite much stronger [5].More interestingly, by combining synthetic fiber with natural fiber, superior mechanical properties can be found yet the footprint of synthetic fibers can be reduced to a great extent.Studies related to hybrid composites by adding glass fiber with the woven jute fiber were already done and the mechanical properties are being found out and compared with pure jute composites [6].Comparing jute and E-glass fiber composites, it is found that jute composites performed poorly compared to E-glass composites due to the latter's superior mechanical properties.However, combining jute and E-glass fibers in a hybrid composition showed better results than using either pure jute or pure E-glass composites, striking a balance between strength and sustainability.The arrangement of fiber layers within the composite structure significantly impacts the flexural and interlaminar shear properties, while also influencing tensile properties to a lesser extent.These findings highlight the potential for optimizing composite performance by carefully selecting fiber types and layer sequences to suit specific application requirements.Among all the natural fibers used as reinforcements in composites, jute stands out to be one of the most promising natural fiber materials due to its cost-effectiveness and easy availability in suitable forms.Its strength and modulus surpass those of certain plastics, making it a viable replacement for conventional fibers in many applications [7].However, the structure of jute fibers poses some challenges.Being multicellular and with non-uniform cross-sections composed of microfibrils, the mechanical and physical properties of jute fibers are not consistent.These variations depend on factors like the geographical origin of the jute plant, the climate it was grown in, and the specific processing techniques applied during fiber extraction and preparation.These fluctuations in properties can influence the overall performance of jute fiber-reinforced composites, necessitating careful consideration during their utilization.The study by Gowda concluded that although the mechanical properties of jute/polyester composites may not be on par with those of conventional composites, they do show superior strength when compared to wood composites and certain plastics [8].Hence, these composites hold promise and could be explored for potential use in future materials and applications.The production of composites using lignocellulosic fibers mixed with thermosetting or thermoplastic polymer matrices has recently been a focus of research.Thermosetting polymer-based composites have limitations, such as brittleness and difficulty in repair, while thermoplastic-based composites offer advantages like impact resistance, thermoforming, and recyclability.In the context of tropical zones such as Bangladesh, coir and jute fibers are identified as suitable options due to their widespread availability and affordability.Both coir and jute fibers are composed of cellulose, lignin, and hemicelluloses, but coir has a higher lignin content, making it weather-resistant and resistant to damage by saltwater.Additionally, coir absorbs less water compared to jute due to its lower cellulose content.Both fibers are environmentally friendly, being biodegradable, recyclable, and renewable, with higher strength and stiffness than the polymer matrices.To create eco-friendly composites, studies regarding hybrid composites were carried out by combining jute and coir fibers [9].Tests revealed that increasing fiber loading improves mechanical properties like flexural strength, flexural modulus, impact strength, and hardness.However, higher fiber loading leads to increased water absorption.The best mechanical properties are observed in the higher fiber-reinforced composite, where strong adhesion between fibers and the matrix is evident through scanning electron microscopy.Chemically treating jute epoxy composites and applying a protective coating resulted in enhanced mechanical properties and reduced moisture absorption [10].The jute mat treated with sodium hydroxide solution improves the adhesion between the jute fibers and the epoxy matrix.Subsequently, the composite was coated with acrylic paint revealing that the chemically treated composite exhibited superior mechanical properties compared to the uncoated composite.Furthermore, the combination of chemical treatment and coating significantly reduced moisture absorption, especially when the specimens were exposed to distilled water with varying pH levels.The mechanical properties of a bi-directional jute fiber epoxy composite have been the subject of quite some research [11].Air trapping during resin preparation and moisture absorption caused cavities to emerge in the polymer composites, weakening the interfacial strength between the fiber and matrix.The void formation decreases with increasing fiber loading percentage.Also, the hardness and flexural strength increased with increasing bi-directional jute fiber loading percentage [11].Integrating the advantages of natural and synthetic fibers to create hybrid composites that make use of the distinctive qualities of each component, producing exceptional but affordable materials.By blending these fibers within the same matrix, the hybrid composites can achieve a balance of properties that surpass those of individual fiber composites.Various research studies have been conducted to explore the potential of hybrid composites.The mechanical and interface properties of sisal/glass-fiberreinforced PVC hybrid composites are reported in the literature [12].In another work, low-density polyethylene-based short sisal/glass hybrid composites observed significant improvements in mechanical properties [13].The hybrid composites are created by randomly arranging short sisal and glass fibers in an unsaturated polyester resin matrix [14].The researchers analyzed the impact of fiber content and chemical treatment on the flexural properties of these hybrid composites.However, when the glass fiber percentage was low, these hybrid composites had poorer flexural characteristics than the matrix.Silane treatment was shown to have no discernible impact on the flexural characteristics of sisal/glass hybrid composites, according to research on the effects of alkali and silane treatments on fibers.Alkali treatment did, however, result in a little improvement in flexural characteristics.Some researchers investigated how to increase the flexural properties of natural fiber-reinforced composite having chemical treatments [15].Alkali treatments with a NaOH solution of 5%, 6%, and 10% had been observed as the primary treatment.A combination of alkali and silane treatments showed higher flexural properties than a single treatment.A composite made from 20 wt.% of pineapple fibers reinforced into the nylon matrix [16].Alkali and silane treatments were used on pineapple fibers.Both flexural strength and flexural modulus were evaluated and results showed that for alkali and silanetreated fibers exhibit more flexural properties than the untreated pineapple fibers.Some investigations were performed on the mechanical properties of chemically treated abaca polypropylene composite with a comparison of untreated abaca fiber [17].This study showed that treated abaca had more flexural properties than untreated abaca.In comparison to composites, steel bonnets have superior mechanical characteristics in terms of strength, stiffness, and hardness.However, due to their significantly reduced weight and improved specific characteristics, carbon fiber-reinforced composites are appealing for applications where weight is an important factor, such as those in the aerospace and automobile sectors [18].The strength, stiffness, and hardness of the composites are improved by the inclusion of carbon fibers.Short fiber composites and other lightweight materials like fiber-reinforced composites are being employed in cars to reduce weight while keeping appropriate strength and performance.Because carbon fiber is brittle, carbon fiber composites may be vulnerable to stress concentration [19].In addition, it costs money to produce carbon fiber.By replacing certain carbon fiber layers with ductile fibers, a process known as hybridization, it is possible to strengthen the weaknesses of carbon fiber-reinforced plastic composites.This method creates unique materials while improving the overall mechanical and physical qualities and perhaps lowering the cost.Park and Jang [20] combined carbon and polyethylene fibers in an epoxy matrix to produce a hybrid composite laminate.The high elongation at break, specific strength, and stiffness of PE fibers were taken into consideration while choosing them.The study showed that the placement of the reinforcing fibers had a significant impact on the hybrid composite's mechanical characteristics.Notably, the hybrid composite showed the best flexural strength when carbon fibers were added to the outermost layer.Investigations into the impact of various carbon and basalt fabric stacking sequences on the flexural characteristics of hybrid composite laminates revealed that the order in which the fiber reinforcement was stacked had a significant impact on the hybrid composite laminates' flexural strength and modulus [21].Significant hybridization effects were seen in all stacking sequences.In a different study, the mechanical properties of composite materials manufactured from flax and carbon fibers were assessed to comprehend how the performance of the final composite was affected by the combination of different fibers [4].They focused on flexural strength and breaking at elongation.The findings demonstrated that using flax and carbon fibers in combination improved breaking at elongation compared to composites composed only of carbon fiber.This indicates that the flax and carbon fiber combination demonstrated greater resilience to breaking under elongation stresses.However, the study also showed that the flexural strength of the carbon composites was decreased as a result of the flax fiber inclusion.Due to flax fibers' intrinsic weakness compared to carbon fibers, the composite's total flexural strength was impaired.This discovery emphasizes the compromises made when mixing various fiber types to create composite materials in terms of specific mechanical qualities Additional investigations into the impact of stacking sequence on the flexural strength of hybrid composites were conducted [22,23].These investigations discovered that putting fiber that is substantially stronger (like carbon or glass fiber) on the composite's exterior increased its flexural strength.Due to their greater exposure to external loads and stresses, the outer layers are crucial in establishing the composite's overall strength.The influence of fiber volume content on the tensile strength of hybrid composites was also investigated by researchers [24].Findings from this study showed that the tensile strength of the composite was enhanced by increasing the fiber volume content.Still, there is plenty of room for additional studies and scope of research regarding hybrid composites to find a better combination that serves both tensile and flexural demands.Especially studies related to the dependency of stacking or ply sequences on mechanical properties are still in the developing stage.This current work focuses on these issues.The objective of this study regarding hybrid composites is to investigate the mechanical properties of jute woven & and carbon-jute woven reinforced polymer matrix composites by changing the stacking sequences of the composites and weight fractions and to draw definite conclusions on their dependencies over mechanical properties.

Methodology
This study is about the mechanical properties of carbon jute composite having different weight fractions and different lamina combinations where carbon fiber is used as synthetic fiber.Two different combinations of wt.fractions were used to manufacture the composites where one was 80:20 and the other was 85:15.The differences in mechanical properties between pure jute composites having the wt.fractions mentioned above and jute-carbon composites were found.Specimens were prepared to maintain the following procedure: • Cutting of Woven Fiber: o Woven jute and carbon fibers were initially cut into the desired size.o Separate layers were prepared for conducting tensile and bending tests.
o The weights of both jute and carbon fibers were measured to calculate their respective weight fractions.

• Resin Weight Measurement:
o Following the fiber measurement and calculations, the required amount of resin was determined.o The resin quantity was measured using a digital weight measuring machine, accounting for some additional resin to compensate for losses during the manufacturing process.

• MEKP Measurement:
o An amount of Methyl Ethyl Ketone Peroxide (MEKP) equivalent to 1% of the weight of the resin was taken.

• Mixing:
o The polyester resin and MEKP were thoroughly mixed in a cup.

5
• Composite Preparation: o The woven fiber was cut into experimental samples, and their weights were measured.o Different weight fractions of polyester resin and MEKP hardener were measured.o The woven carbon and jute fibers were then sequentially placed on maillot paper.o The measured polyester resin was mixed with the calculated amount of MEKP to form the matrix.o The woven carbon and jute fibers were impregnated with the matrix during the composite preparation process.o The composite was manufactured, and the final step involved rolling it to achieve a smoother surface and compressing it with weights for 24 hours.o The prepared material was observed and cut to the desired testing dimensions using a grinder machine.

• Test Specimen Preparation:
o After machining, the composite was cut into the required dimensions for testing.

Table 1. Fiber and matrix properties
At first, woven jute and carbon fiber were cut into the desired size.Different layers were cut for tensile and bending tests.After that, the weight of the jute and carbon fibers was measured for weight fraction calculation.After measuring the fiber and from the calculation, the amount of resin needed was found.That amount of resin was measured in a digital weight measuring machine with some extra amount of resin which was lost during the manufacturing process.1% weight of the resin was taken as the amount of MEKP.The polyester resin and MEKP were mixed in a cup.The woven fiber was cut into samples for the experiment and the weight was measured.Polyester resin and M.E.K.P hardener were measured for different weight fractions.The woven fiber was placed on the maillot paper.The weighted polyester resin was mixed with the weighted methyl ethyl ketone peroxide (M.E.K.P) hardener for the preparation of the matrix.Woven carbon and jute fiber were placed sequentially and mixed with the matrix and thus the composite was manufactured.In the final step, the composite was rolled for a smoother surface and was compressed with weights for 24 hours.In this step, the prepared material is observed and cut by a grinder machine into testing dimensions.After machining the surface of the composite was polished with emery paper for smooth surface finishing.For the tensile test, the geometry of the test specimen is shown in Fig. 1.The test was performed following ASTM D3039.Specimens 140-170 mm in length and 15-17 mm wide were cut from the laminate such that the jute warp yarns were oriented along the length of the specimen.Tensile stress was calculated using equation (1).
where F, applied force; A, cross-sectional area The strain was calculated using equation ( 2) where ΔL, deflection of length; L, initial length Young's modulus was calculated using equation ( 3) where E, Young's modulus; σ, stress; ε, strain The weight of the composite was calculated theoretically as equation ( 4) Weight fraction of fiber, where Wf, is reinforcement fiber weight fraction (%); wf, is the weight fraction of fiber; wc, is the weight of the composite.The weight of the matrix was calculated theoretically as equation ( 5) where wc, is the weight of the composite, wf is, the weight of reinforced fiber, and wm, is the weight of the matrix.The volume fraction of fiber was calculated using equation ( 6) Volume fraction of (Vf)= where Vf, is the volume fraction of fiber; vf, is the volume of fiber; and vc volume of composite.
The volume fraction of the matrix was calculated using equation ( 7) where Vf is, the volume fraction of fiber; vc is, the volume of the matrix; and vc volume of the composite.
Flexural Test (Bending Test): The flexural test, also known as the bending test, is performed to determine a material's flexural strength, stiffness, and deformation characteristics when subjected to bending forces.This test is particularly important for assessing the suitability of materials for structural applications, such as beams, columns, and other load-bearing elements.A standardized rectangular specimen with specific dimensions is prepared from the material being tested.The specimen's length and width are measured, and its thickness is typically determined based on the material's characteristics and testing standards.The flexural test was conducted as per ASTM D790.Specimens of 130mm in length and 10mm wide were cut from the laminate.Specimens were loaded in three-point bending with a recommended spanto-depth ratio of 16:1 as shown in Fig. 2. The flexural stress in a three-point bending test is given by equation ( 8) where Pmax, maximum load at failure (N); L, is the span (mm); b, width(mm); h, thickness(mm) of the specimen (mm), respectively.The flexural modulus is calculated from the slope of the initial portion of the load-deflection curve.Flexural modulus is given by equation ( 9) where E is, the modulus of elasticity; m, is the initial slope of the load-deflection curve.For each stacking sequence, three specimens are tested and the average result is obtained.

Tensile Test
The tensile test has been done using an EQUIPMENT UNIVERSAL TESTING MACHINE (UK) having a load range of up to 100kN.Table 1 presents the nomenclature of six specimens, each with distinct laminate stacking sequences and varying fiber weight fractions, intended for the tensile test.The tensile strength, elongation-at-break, and Young's Modulus are documented in Table 2 and Figure 4.1.Notably, Specimen 1, comprising 20% fiber weight fraction with jute fiber, exhibited the highest stress at 32.115 MPa and Young's Modulus at 1.308 GPa, surpassing the one with 15% fiber weight fraction, both employing only jute fiber as reinforcement.Among the four groups of carbon-jute composite samples, Specimen 3, characterized by the stacking sequence J/C/J/C/J with 20% fiber content, displayed the highest tensile strength at 108.795 (±10.8815)MPa, along with the maximum Young's Modulus of 6.052 GPa, outperforming all other six groups.The experimental results revealed significant variations in the flexural properties of composite specimens with varying weight fractions of carbon and jute fibers.Notably, the hybrid composite S3 with a 20% weight fraction having a stacking orientation of alternate ply of jute mat and carbon mat exhibited the highest flexural strength and modulus among the group.For composites made of pure jute mat, 15% fiber weight fractions registered superior values of flexural stress and modulus as 69.762MPa and 3.225 GPa, respectively.Specimen 3 (S3), which incorporated a layer of carbon fiber between each jute layer, exhibited a remarkable increase in strength by approximately 112.25%, reaching a flexural modulus of 6.845 GPa.Conversely, Specimen 4, with a similar stacking sequence but containing 85% matrix and 15% fiber, demonstrated lower strength when compared to Specimen 3. The addition of carbon fiber in conjunction with jute fiber notably altered the composite properties, leading to delamination in all groups from Specimen 3 to Specimen 6.Among the carbon-jute composite samples, Specimen 3, with the stacking sequence J/C/J/C/J/C/J/C/J and 20% fiber content, exhibited the highest maximum stress maybe since the interlocking i.e. the adhesion between matrix and fiber mats for alternate layers increased to a great extend which resisted the bending force resulting superior outcome.
As seen in Figure 4.6, higher fiber mat content increased the flexural properties for pure Jute and alternate stacking sequences of Jute mat and carbon mat in hybrid formation.But an exception is observed in the case of hybrid configuration where two same mats are applied together having three pairs of jute mats sandwiching two pairs of carbon mats.This may maybe due to the fact that adding more fiber mats in this specification of layers does not aid in flexural properties but rather exhibits poor adhesion.From Figure 4.9, it can be observed that for S1 and S2 i.e. for the jute mat composites the deformation is smooth until the onset of failure.However, for the hybrid composites, there is clear evidence of having failures of separate layers.As seen, the red and purple graphs (twin layers of the same mat, S5, and S6) showed similar behavior with an offset of value until deflection reached 15 mm.The S3 sample showed the best performance after the failure of the jute mat layer, the load was carried by the carbon layer and once that failed, the sample failed drastically.

Conclusion
Hybrid composites are materials that combine two or more different types of fibers, each with unique properties, to create a material with improved mechanical characteristics.The tensile strength of a hybrid composite can be affected by the volume fraction of the fibers used.To further enhance the tensile strength of the hybrid composite, the placement of carbon mats is crucial.When the carbon mats are placed centrally within the composite, it enhances the interaction between the carbon fibers and the surrounding matrix material, which is usually a polymer.This proximity allows for better load transfer between the carbon fibers and the matrix during tensile loading, effectively improving the overall strength of the composite.One of the critical issues that can affect the tensile strength of a composite is debonding and delamination.By placing the carbon mats centrally and enhancing the carbon interaction, the likelihood of debonding and delamination is reduced.The improved adhesion between the carbon fibers and the matrix prevents them from separating easily under load, contributing to a more robust composite.The use of carbon fibers is another significant factor that contributes to the increase in tensile strength.Carbon fibers are known for their exceptional strength and stiffness compared to natural fibers like jute.When the hybrid composite is composed mainly of carbon fibers, it inherits these superior mechanical properties, leading to a sharp increase in tensile strength.The findings from this work suggest that the flexural strength of composite laminates can be improved by placing carbon fiber layers on both the compressive and tensile sides, as carbon fibers have a higher load-bearing capacity than jute fibers.Conversely, adding jute fiber layers to the compressive side reduces the material's ability to withstand flexural forces.To achieve high flexural strength, carbon fiber jute was positioned on the outermost layers of the composite, where it effectively carries the majority of the flexural load during application.The stacking sequence with JC in the composite laminate demonstrated greater flexural strength compared to JJ in the outer layers.

Figure 1 . 6 2x2
Figure 1.Stepwise process for preparing composite sample using hand layup method: a) Fiber Weight Measurement, b) Resin Weight Measurement c) MEKP Measurement d) Mixing e & f) Composite Preparation g) Test Specimen Preparation

Figure 5 .
Figure 5.Samples for flexural test

Figure 10 .Figure 11 .
Figure 10.Summary of the six different samples tested for (a) tensile strength, (b) Young's Modulus

Figure 13 .Figure 14 .
Figure 13.Summary of the six different samples tested for (a) flexural strength, (b) flexural modulus

Figure 15 .
Figure 15.Force vs. Deflection graph of all specimens

Table 2 .
Laminate stacking sequence for tensile test

Table 2
highlights the variation in tensile properties of woven jute concerning changes in weight fraction.Specifically, the incorporation of 5% more woven jute resulted in an approximate 103% increase in Young's Modulus.Furthermore, Specimen 3, featuring a layer of carbon fiber mat between each layer of woven jute mat, demonstrated a remarkable strength increment of over 230%, achieving 6.052 GPa.

Table 3 .
Tensile force, strength, and modulus of composites

Table 4 .
The flexural test was carried out in the HOUNSFIELD UNIVERSAL TESTING MACHINE which has a load cell of 10kN.Table3indicates the nomenclature of all six specimens with various laminate stacking sequences and different fiber weight fractions for the flexural test.Table4 and Figure4.6 & Figure 4.7 indicate the flexural strength and flexural modulus.Laminate stacking sequence for bending test

Table 5 .
Flexural force, strength, and modulus of composites