studying the mechanical properties of composites made of kenaf-nylon 66 fabric, silica...

Studying the Mechanical Properties of Compositesmade of Kenaf-Nylon 66 Fabric, Silica Nanoparticles,and Epoxy Resin

Masoud Alizadeh,1 Farshad Lohrasby,2 Ramin Khajavi,3 Naser Kordani,4 Hamid Reza Baharvandi,5

Moein Rezanejad6

1Department of, Textile Technology, Islamic Azad University, South Branch, Tehran, Iran

2Department of Textile Technology, Islamic Azad University of Arak, Arak, Iran

3Department of Textile Chemistry, Islamic Azad University, South Branch, Tehran, Iran

4Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran

5Department of Materials Engineering, Tehran University, Tehran, Iran

6Technical University of Mirza koochak, Guilan, Iran

In this study, the effect of the relationship betweenyarn material and yarn count tex on the mechanicalbehavior of plainly woven hybrid fabrics impregnatedwith Silica nanoparticles and Epoxy resin has beeninvestigated. First, various types of bicomponent andsingle-component fabrics with plain weaves are pre-pared using kenaf and Nylon-66 yarns with yarn texcount of 334 and 427. To prepare the composite, Silicananoparticles with a particle size of 200 nm aremechanically mixed into Glycol Polyethylene with amolecular weight of 200 along with Ethanol in propor-tions of 6:1. The weight percent of Silica particles inthe suspension has been selected as 60%. Using around edge indenter, the concentrated indentationforce test has been performed based on the 6264Dstandard to determine the strength of each fabric sam-ple. Then, by impregnating the mentioned fabrics withpolymer materials (Silica nanoparticles and epoxyresin) and performing the concentrated force testsagain, it is found that the hybrid fabrics with a yarn texcount of 427 and impregnated with polymer materialenjoy the highest shear thickening properties. POLYM.COMPOS., 00:000–000, 2014. VC 2014 Society of PlasticsEngineers

INTRODUCTION

The increase in environmental awareness throughout

the world is influenced to a large extent by the engineer-

ing and design of various materials.

The growing interest in the use of natural materials is

due to a higher concern for environmental issues such as

recycling and environmental safety. Presently, artificial

fibers such as glass, carbon, and Aramid are extensively

used in composites based on polymer material, due to

their high strength and toughness [1]. However, these

fibers have serious drawbacks in terms of decomposition,

production cost, recycling, and health hazards [2].

Recent research reveals that the use of natural fibers has

been increasing in plant composites. In fact, comparisons

of natural fibers and synthetic fibers that we will find natu-

ral fibers have better properties. In certain case have biode-

gradability, part of renewable resources and for produce

they do not require much energy. While the one-piece com-

posite made of synthetic fibers material after finishing it is

life remains in nature, even this problem remains by burn-

ing a piece of composite. So we can stay that in the future

the natural fibers are a good alternative to synthetic fibers.

Natural fibers such as hemp, flax, and kenaf have been

known as good candidates for the reinforcement of com-

posites [3, 4]. The successful use of these fibers depends

on their structural and mechanical properties. These char-

acteristics depend on the location where these plants

grow, the climatic conditions, and the age of the plants.

Correspondence to: Masoud Alizadeh;

e-mail: [email protected]

DOI 10.1002/pc.23224

Published online in Wiley Online Library (wileyonlinelibrary.com).

VC 2014 Society of Plastics Engineers

POLYMER COMPOSITES—2014

These factors determine the coefficients of the fibers’

properties [2–4]. Moreover, the increase in the mechani-

cal properties of natural fibers depends on the amount of

cellulose contained in the structure of those fibers, which

can be observed in Table 1 [2–4].

By modifying the makeup of these fibers, the research-

ers are trying to arrive at a suitable combination of fibers

and resin that enhances the strength and effectiveness of

the obtained composite in order to secure an appropriate

and sure position in the composite industries market [3].

Low weight, high modulus, nontoxicity, low energy

consumption during production and Carbon Dioxide

absorption during the growth are the important character-

istics of these types of natural fibers [5, 6].

However, natural fibers have certain flaws in some of

their properties. The structural components of natural

fibers, including cellulose, lignin, pectin, and ash, can

absorb moisture from the surrounding environment, which

will lead to weak bonds between them and polymer mate-

rial [7]. Therefore, in addition to the chemical structures

of fibers and different matrixes, the weakness in the

attachment location of the two material phases can deteri-

orate the mechanical properties of the composite material.

Hence, special chemical treatment is needed on the sur-

face of natural fibers. This treatment is normally carried

out by applying chemical materials that can react with

fiber structure and modify its constituents so that the

fibers become less inclined to absorb moisture and more

adapted to polymer matrix [5]. Modifying the bonds

between the surfaces of fibers and matrix can improve the

mechanical properties of the composite [8].

Wambua et al. investigated the ballistic properties of

polypropylene composites reinforced by hemp, flax, and

kenaf fibers produced by the hot pressing technique. They

also explored the ballistic performance of composites

reinforced by steel plates (bonding steel plates to front

and back surfaces of the composite). They showed that

the ballistic limit of composites made of natural fibers

increases nonlinearly by increasing the thickness and sur-

face density. Flax composites had higher energy absorp-

tion relative to kenaf and hemp composites. Due to the

fragility and lower strength of their fibers, kenaf compo-

sites showed the lowest kinetic energy absorption

capacity. By adding the steel plate layers, the ballistic

properties of hemp composites improved [9].

Cheeseman, Bogetti, and Cuniff stressed that the fabric

structure, number of fabric layers, surface density (g/m2),

interaction between fabric layers, friction between fibers,

boundary conditions, and the friction between fibers and pro-

jectile are important factors in the absorption of impact

energy by high-tenacity fabrics [10, 11]. Gadow and Niessen

[12] demonstrated that ceramic coating by plasma on the uti-

lized fibers enhances the performance of the composite panel.

Ahmad et al. [13] maintained that a natural latex coating

on high-modulus fabrics increases the ballistic performance

of the fabricated panel. Lee et al. [14] found out that saturat-

ing the fabric with a shear thickening fluid, without increas-

ing the thickness and stiffness of the fabric, improves the

strength and tenacity of the resulting composite.

The goal of this study is to make a high-strength,

impact-resistant, and low-cost composite that can be a

good substitute for composites made of ceramic and Kev-

lar, carbon or glass fibers. First, the hybrid fabrics (Kena-

fand Nylon 66) and the plain Kenaf fabric are

impregnated with the composite made of silica nanopar-

ticles and epoxy resin and then, by conducting the con-

centrated indentation force test, the mechanical properties

of each sample are investigated. As the concentrated load

is applied to the fabric surface, it creates tensile force in

the yarns, and consequently, the concentrated load

changes into a nonconcentrated load. The force dissipation

capacity of the composite fabric depends on different fac-

tors including the fabric material (fiber material), type of

fabric weave (interweaving of warp and weft yarns), yarn

tex count, yarn density, material type of the impacting

object, velocity of impact, and the number of fabric layers.

The overall purpose of this article is investigating

strength of hybrid fabrics in relationship between gender and

yarn count. This issue was discussed that the addition of

polymer to fabric increases the amount of energy absorption.

EXPERIMENTAL TESTS

Material

High-Tenacity Fabrics. In this research, two types of

fabrics, one woven of all kenaf fibers and the other woven

of kenaf fibers (as warp yarns) and Nylon-66 fibers (as

weft yarns), have been used to make the composite. It is

notable that, in weaving this fabric, Nylon-66 fibers with

two different tex count s have been utilized. The specifica-

tions of the mentioned fabrics have been listed in Table 2.

In order to make the fabric hydrophilic to better absorb

the material, the hydrophobic surface of kenaf fibers are

treated with alkali material to create a good compatibility

between the fibers, nanocomposite fluid and epoxy resin.

Reasons for Presaturated With Alkalis.

1. The natural fiber surface is hydrophobic after the presaturated

operation, the rate of moisture absorption of shear thickening

fluid and epoxy resin increases.

2. Because the weighted density of natural fibers is much higher

than synthetic fibers. In presaturated process, materials like

ash, lignin, and pectin separated from natural fibers and the

cellulose is left alone. This action increases the mechanical

TABLE 1. Percentage of the main component of natural plant fibers.

Fiber Cellulose (%) Lignin (%) Pentosan (%) Ash (%)

Ramie 70–91 2–4 5–8 2–4

Kenaf 44–57 15–19 22–23 2–5

Jute 45–63 21–26 18–21 0.5–2

Seed flax 43–47 21–23 24–26 5

Hemp 57–77 9–13 14–17 0.8

2 POLYMER COMPOSITES—2014 DOI 10.1002/pc

properties of the fibers eventually will lead to weight loss in

the final composite.

By impregnating the kenaf fibers with alkali material,

impurities such as ash, lignin, and pectin are separated

from the fibers. So, the fabric is immersed in Acetone

solution for 60 min. Then the sample is taken out of the

acetone solution and left at room temperature for 48 h to

completely dry out.

Polymer Material. Glycol Polyethylene 200 made by

Merck of Germany was used as the carrier fluid and 200

nm spherical Silica particles were utilized as the solid

part of the polymer medium.

Epoxy resin LE-828 and Hardener 1150 (with resin-to-

hardener proportion of 4:1). Amount of the hardener 1 gr

and epoxy resin 4 gr have selected.

Synthesis of Polymer Material From Silica Nanoparticles

The nanocomposite fluid made of 60 wt% Silica nano-

particles and 40 wt% Glycol Polyethylene is mixed with

Ethanol in proportions of 6:1. Then the solution is thor-

oughly mixed in a homogenizer device (Model: Turrax

T50 Basicultr) for 20 min at a rotation speed of 5,000

rev/min as shown in Fig. 1a and then placed into the

ultrasound device (Model: BANDELIN 3200) as shown

in Fig. 1b. The ultrasound equipment uniformly disperses

the particles into the solution by imparting sonic energy

to the solution for about 60 min. During this time, 20

kHz of acoustic energy has been applied to the particles

by the ultrasound machine (2 pulses/s). It should be men-

tioned that all the stages of preparing the solution from

Silica nanoparticles have been carried out at the tempera-

ture of 15�C.

Making the Composite From Silica Nanoparticles

First, the fabrics are cut into 152 3 152 mm2 samples

and then each sample is immersed in acetone solution for

60 min. Then the sample is taken out of the acetone solu-

tion and left at room temperature for 48 h to completely

dry out. The fabric is immersed for 1 min in the fluid of

Silica nanoparticles and Glycol polyethylene that has

been diluted by Ethanol. After removing the fabric from

the solution, we use a steel roller to apply an equivalent

pressure of 12 kg to the surface of the fabric. This drives

out the excess material from the fabric and causes the

nanoparticles to thoroughly permeate the surface of the

fibers. Then the sample is hung at room temperature for

48 h so that the ethanol is evaporated.

Making the Composite From Epoxy Resin

In samples impregnated with epoxy resin, the fabric is

treated for 24 h with 1% Silane (1 cc Silane in 99 cc

Ethanol). Silane is used as a chemical binder or adapting

agent to improve the continuity and adhesion between the

fibers and the thermoset matrix. After the fabric is

TABLE 2. Specifications of fabrics used in making the composites.

Yarn count (tex) material Density (10 cm)

Fabric type Weave type Warp Weft Warp Weft Warp Weft Weight (g/m2)

Kenaf fabric Plain 1519 507 Kenaf Kenaf 37 34 724

Hybrid fabric Plain 1519 427 Kenaf Nylon-66 41 29 744

Hybrid fabric Plain 1519 334 Kenaf Nylon-66 43 31 740

FIG. 1. Equipment used to prepare the polymer material from Silica nanoparticles; (a) Homogenizer device,

(b) Ultrasound device. [Color figure can be viewed in the online issue, which is available at wileyonline

library.com.]

DOI 10.1002/pc POLYMER COMPOSITES—2014 3

impregnated with Silane, the sample is dried at a temper-

ature of 60�C for 20 min, and then a hairbrush is used to

spread the epoxy over the fabric. Images of specimens

are in Figs. 2 and 3. Scanning electron microscope (SEM)

image of fabric impregnated with the shear thickening

fluid with 60 wt% concentration of Silica nanoparticles at

different magnification are in Figs. 4, 5.

TEST CONDITIONS

Quasi-Static Puncture Test

In this study, the strength and tenacity of single-

component and bicomponent fabrics with simple weaves

made of kenaf and Nylon-66 fibers has been investigated

experimentally. The samples have been prepared as

untreated fabrics and fabrics impregnated with shear

thickening fluid and epoxy resin. The square fabrics are

placed as a single layer between two steel frames 40 mm

thick and with 200 mm sides. The diameter of the interior

circle in the middle of two metal plates is 127 mm. As

shown in Fig. 6, these two plates are attached to each

other by means of four bolts, and a circular O-ring is

used to fill the gap between the sample and the frame

and to prevent the fabric from slipping during the test.

The concentrated force test has been performed based

on the D66264 standard by the INSTRON device

(Model: 8502) at a speed of 6 mm/min. In this test, to

exert the concentrated load on a the surface of a 152 3

152 mm2 square fabric, a steel round-edged indenter

with the cylinder diameter of 12.7 mm and the edge

length of 25 mm has been used. Based on the mentioned

standard, the thicknesses of the samples should not differ

by more than 0.1 mm. The test has been repeated five

times for each sample. The round-edged indenter tool

used for applying the concentrated force and device

used for the concentrated force test are shown in Figs. 7

and 8.

The following procedure was implemented to get the

weights of the untreated sample and the fabric samples

impregnated with the shear thickening fluid and epoxy

resin:

First, the untreated fabric sample was placed inside an

oven at a temperature of 60�C for 10 min and then it

was placed inside a Silica gel chamber for 5 min. After

that, the weight of the sample was measured. These steps

were repeated until a constant weight was obtained. In

this way, the weight of the untreated sample and conse-

quently the weight of the sample impregnated with the

fluid containing the Silica nanoparticles are obtained

(Table 3).

FIG. 2. Images of Kenaf fabrics; (a, b) Plain (untreated) kenaf, (c, d) Kenaf impregnated with Silica nano-

particles/Glycol polyethylene, (e) Kenaf treated with epoxy resin (magnification up to 340). [Color figure

can be viewed in the online issue, which is available at wileyonlinelibrary.com.]


RESULTS AND DISCUSSION

Results and Discussion Regarding the ConcentratedForce Test

In Fig. 9, the effect of the epoxy resin and nanofluid

on the increased penetration resistance of kenaf fabric is

evaluated. Through a close examination of this figure, it

can be realized that both the shear thickening fluid and

epoxy resin prevent the sliding and slipping of the fibers,

but the effect of the epoxy resin is greater than that of

the thickening fluid. The reason for this discrepancy is

the mechanism by which each of these materials act

on the fibers. The shear thickening fluid prevents the

FIG. 3. Images of hybrid fabrics; (a, b) Plain (untreated) hybrid fabric, (c, d) Hybrid fabric impregnated

with Silica nanoparticles/Glycol polyethylene, (e) Hybrid fabric treated with epoxy resin (magnification up to

340). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIG. 4. SEM image of fabric impregnated with the shear thickening

fluid with 60 wt % concentration of Silica nanoparticles at a magnifica-

tion of 1006.

FIG. 5. SEM image of fabric impregnated with the shear thickening

fluid with 60 wt % concentration of Silica nanoparticles at a magnifica-

tion of 4022.


slipping of the fibers by increasing the friction between

them and also prevents the tearing and rupture of fibers

by the accumulation of particles at the point of impact;

while the epoxy resin, through having superior mechani-

cal properties, increases the breaking strength of the

fibers and also prevents the fibers from sliding by stick-

ing them together. Thus, in the sample impregnated with

the shear thickening fluid, the penetrating object ulti-

mately passes through the sample fabric by sliding and

pushing away and also tearing the fibers. In the sample

treated with epoxy resin, since it is not possible to cause

the fibers to slip and slide, the penetrating object can

only penetrate the composite sample by tearing and

breaking the fibers.

Figure 10 shows the effects of epoxy resin and shear

thickening fluid on the penetration resistance of hybrid

fabrics made of Nylon yarns with tex count s of 34 and

427. In the hybrid fabric impregnated with polymer mate-

rial, Nylon fibers in combination with kenaf fibers are

able to improve the penetration resistance; because the

Nylon fibers, as a backup to kenaf fibers, prevent the

tearing of the kenaf fibers by distributing the energy of

impact over the fabric surface; and also the kenaf fibers,

by creating friction, prevent the Nylon fibers from slip-

ping and sliding. Conversely, the shear thickening fluid

also helps increase the friction between the fibers. Ulti-

mately, all these factors together lead to the increase in

the breaking strength of fibers. As anticipated, in this

hybrid fabric also, the highest resistance is observed in

the sample treated with epoxy resin. The concentrated

force test on the fabrics by means of the round-edged

indenter is shown in Fig. 11.

As is observed in Fig. 12, the effects of epoxy resin

and nanofluid can be clearly seen. Left figures (a1, b1)

are front and right figures (a2, b2) are rear of the sam-

ples. In the untreated fabric samples, more slipping can

be observed in the yarns. Thus, by pushing away the

yarns, the indenter creates a hole in the untreated sample.

However, in the samples impregnated with Silica nano-

particles and epoxy resin, due to the increased friction,

the amount of slippage is reduced and all the yarns

engaged with the indenter resist the force of impact to the

point of rupture. The concentrated force test on the

single-layer hybrid fabric (using 427 tex Nylon yarns) by

means of the round-edged indenter is shown in Fig. 13.

By analyzing the data, we can clearly realize that, in

addition to polymer material, other factors such as fiber

material (properties of fibers) and yarn tex count are also

effective in the improvement of penetration resistance.

By examining the tested fabrics more closely, we see

that the untreated kenaf fabric shows the highest

FIG. 6. Steel frame for holding the fabric in the concentrated indenta-

tion force test. [Color figure can be viewed in the online issue, which is

available at wileyonlinelibrary.com.]

FIG. 7. The round-edged indenter tool used for applying the concen-

trated force.

FIG. 8. INSTRON-8502 device used for the concentrated force test.

[Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com.]

TABLE 3. Weights of the sample before and after impregnation with

polymer material, in the concentrated force test (Weight

(152*152 mm2)).

Fabric type Untreated

Shear

thickening fluid

Epoxy

resin

Kenaf fabric 14.8 26 36.1

Hybrid fabric count (tex) 334 15.8 25.5 36.5



resistance; however, with the addition of polymer materi-

als to the fabrics, the highest penetration resistance is

observed in the hybrid fabric sample with yarn tex count

427. Another significant issue in this study is the way the

indenter penetrates the untreated samples. In kenaf fabric

samples, it is observed that the indenter has completely

torn the kenaf fibers; but in the test of the hybrid fabric,

after breaking the kenaf fibers, the indenter has pushed

away the Nylon fibers and passed by them, causing the

least amount of damage. It should be noted that the fabric

resistance against the indenter increases as Nylon fibers

with lower tex counts are used in the untreated hybrid

fabrics; in other words, there is less slippage in higher

capacity Nylon fibers.

In single-layer composite samples, when the penetrat-

ing object pushes on the surface of the hybrid fabric, its

penetration is resisted by both the Nylon and kenaf yarns

together. Since kenaf has a lower resistance compared to

the Nylon fiber, the load applied on kenaf yarns are trans-

ferred to the Nylon weft yarns and, in this way, the

imparted energy is distributed in the fabric. As the yarn

tex count increases in a hybrid fabric, the impact energy

is distributed over a vaster surface. Consequently, the

Nylon fibers play a more effective role in resistance

against penetration, and instead of slipping; they resist to

the point of rupture and also improve the distribution of

energy through the fabric.

The concentrated force test was conducted on single-

component and bicomponent fabrics with two layers (with

the layers rotated 0� and 90� relative to each other). In

this investigation, the effects of polymer materials (nano-

fluid and epoxy resin) were also considered. The first

sample consisted of a two-layer untreated fabric, and the

second sample consisted of one layer of fabric treated

with epoxy resin (as the upper layer) and another layer of

fabric impregnated with nanofluid (as the lower layer). It

should be mentioned that the layers impregnated with

nanofluid are dried and then added to the layers treated

with the epoxy resin. Obviously, the resistance of the sec-

ond sample will be much higher than that of the plain

(untreated) fabric sample.

When the intender exerts the force of impact to the

first layer (treated with epoxy), this layer transfers the

load to the backup layer (treated with nanofluid). Since

the second layer is more flexible compared to the first

layer, it distributes the applied force over a larger area,

and this leads to an increase in penetration resistance.

Thus, the resistance to penetration in two-layer fabrics

treated with polymer material is considerably higher than

FIG. 9. The concentrated force test on the single-layer kenaf fabric by

means of the round-edged indenter. [Color figure can be viewed in the

online issue, which is available at wileyonlinelibrary.com.]

FIG. 10. The concentrated force test on the single-layer hybrid fabric

(using 334 tex Nylon yarns) by means of the round-edged indenter.



FIG. 11. The concentrated force test on the fabrics by means of the round-edged indenter; (a) Single-layer

hybrid fabric with kenaf/nylon yarns, (b) Single-layer kenaf fabric. [Color figure can be viewed in the online

issue, which is available at wileyonlinelibrary.com.]


that in untreated two-layer fabrics. The concentrated force

test on the two-layer kenaf fabric by means of the round-

edged indenter is shown in Fig. 14.

An interesting point is that, in testing the untreated

two-layer kenaf fabric and hybrid fabric, a higher resist-

ance is observed in the kenaf fabric sample. This can be

attributed to an increased friction between fibers and

indenter surface and between the fibers themselves, which

causes the kenaf fibers to resist to the point of breaking;

whereas in the untreated hybrid fabric sample, with the

increase of the applied force, the Nylon fibers slip and

cannot put up an ultimate resistance.

In the two-layer composite samples, as the penetrating

object impacts the surface of the hybrid fabric, the force

is exerted first to the hard epoxy composite front layer,

which transfers it to the more flexible back layer to

spread it over a larger area. Since this is a two-layer sam-

ple and the number of involved Nylon yarns is twice that

of the single-layer case, it can be concluded that the com-

posite containing the hybrid fabric has an increased resist-

ance against indenter penetration relative to the kenaf

composite sample. The concentrated force test on the

two-layer hybrid fabric (using 334 and 427 tex Nylon

yarns) by means of the round-edged indenter is shown in

Figs. 15 and 16. Thicknesses of the sample in (mm)

before and after impregnation with polymer material, in

the concentrated force test are in Table 4.

FIG. 12. Effects of epoxy resin and nanofluid (a1, b1) are front, (a2, b2) are rear of the samples. [Color

figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIG. 13. The concentrated force test on the single-layer hybrid fabric




FIG. 14. The concentrated force test on the two-layer kenaf fabric by

means of the round-edged indenter. [Color figure can be viewed in the

online issue, which is available at wileyonlinelibrary.com.]


In this research, first, a kenaf fabric sample and, then,

hybrid fabric samples with Nylon yarn tex count s of 334

and 427 underwent impact tests by the quasi-static con-

centration force test. Then, by adding the Silica nanofluid

(shear thickening fluid) and epoxy resin to the samples,

the tests were repeated.

After obtaining the results of the tests and comparing

them with each other, it was found that in the untreated

samples, the highest penetration resistance belongs to the

kenaf fabric. The reason for this is the fiber–fiber and

fiber-indenter frictions which cause an increased friction

and engagement between the yarns and indenter in the

sample made of kenaf. In the hybrid fabrics, although the

weft yarns are made of Nylon and have a high breaking

strength, but due to the slippery nature of Nylon fibers,

the mentioned strength is not fully developed and these

fibers slip past the indenter. However, with the use of

polymer material, the Nylon fibers too fully engage the

indenter and resist its penetration to the point of rupture.

That is why the fabric sample containing the 427 tex

Nylon yarns, after being treated with the polymer mate-

rial, displays the highest resistance against penetration.

An interesting point is that, after using the nanofluid

and epoxy resin in the two-layer composite samples, the

resistance against indenter penetration increases in the

kenaf composite sample, hybrid sample with the 334 tex

Nylon yarns and the hybrid sample with the 427 tex

Nylon yarns by 11%, 17% and almost 37%, respectively.

Based on the analyses performed on the results of con-

centrated force tests, there is a large difference in the per-

cent increase of penetration resistances in the kenaf

composite sample, from the case in which fluid with

Silica nanoparticles is used to the case where epoxy resin

is used; however, this difference is less pronounced in the

hybrid fabric. This means that, in the composites made of

hybrid fabrics treated with nanofluid, a higher growth in

penetration resistance has been observed relative to the

composite sample made of kenaf. Because by accumulat-

ing the particles at the point of impact and by increasing

the amount of abrasion, this nanofluid has been able to

reduce the degree of slippage of Nylon yarns in the

hybrid fabrics.

In this study, the general effect of friction on the

resistance of fabrics against indenter penetration was

investigated and it was determined that this penetration

resistance depends on factors such as the friction between

the steel indenter and fabric, friction between fibers them-

selves and the type of fibers. The results of the above-

mentioned test on the sample treated with nanofluid

indicate the increased resistance of this sample relative to

the untreated sample due to the accumulation of particles

at the impact location and also the increase in the fiber-

on-fiber sliding resistance at junctions where the fibers

cross one another. In other words, the nanofluid modifies

the abrasion existing between the internal fibers and the

friction between the yarns themselves. Since the fabric

has a taffeta type weave, there are more upper and lower

points on the yarns that form the fabric, and this facili-

tates the distribution of the applied force over a larger

surface and, therefore, the absorption of a greater force.

It should be mentioned that in the concentrated force

test, the types of yarns, nanofluid and epoxy resin have a

significant effect on the resistance against indenter pene-

tration; however, with the change of yarn tex count in the

hybrid fabric, they show little effect on the increase of

penetration resistance.

FIG. 15. The concentrated force test on the two-layer hybrid fabric




FIG. 16. The concentrated force test on the two-layer hybrid fabric




TABLE 4. Thicknesses of the sample in (mm) before and after impreg-

nation with polymer material, in the concentrated force test.

Fabric type Untreated

Shear

thickening

fluid

Epoxy

resin

Kenaf fabric 1.66 1.68 1.64




CONCLUSIONS

The research outlined in this article has reached the

following conclusions:

1. The highest resistance against penetration in the untreated

fabrics is displayed by kenaf fabrics. The next highest

penetration resistance belongs to the hybrid sample con-

taining the 334 tex Nylon yarns. As the yarn tex count

goes up in the hybrid fabric, the slippage of yarns increase

during the impact of the indenter with the surface of fab-

ric and, on the contrary, as the tex count becomes smaller,

the amount of slippage diminishes.

2. The highest resistance to penetration in the presence of

Silica nanoparticles and epoxy resin is displayed by the

hybrid sample containing the 427 tex Nylon yarns. In

these conditions, with the increase of Yarn tex count, the

resistance against indenter penetration increases as well.

3. The fabric sample impregnated with fluid containing

Silica nanoparticles has a lower penetration resistance

than the sample treated with epoxy resin.

4. Natural fibers display less slippage compared to manmade

fibers. This is because there is more friction and entangle-

ment between natural fibers than between artificial fibers.

5. The degree of increase of penetration resistance in the

kenaf fabric, from the untreated sample to the sample

treated with fluid containing Silica nanoparticles is less

than that in the hybrid fabric under the same conditions.

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studying the mechanical properties of composites made of kenaf-nylon 66 fabric, silica...

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