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v1

1 Article

2 Influence of the Quantity of Water Absorption in the

3 Mechanical Properties of Jute Fiber and Glass Fiber
4 Composites
5 Camilla Medeiros Dantas 1, Raimundo Carlos Silverio Freire Júnior 1, Jayna Kátia Dionisio dos
6 Santos 2, Camilla Cruz da Silva 3, Elmo Thiago Lins Cöuras Ford 1*
7 1 Federal University of Rio Grande do Norte. Natal, RN – Brazil;
8 2 Federal Institute of Science Education and Technology of Ceara, Jaguaribe, CE – Brazil;
9 3 Federal Institute of Science and Technology of Bahia, Vitória da Conquista, BA – Brazil;
10
11 * Correspondence: elmocouras@hotmail.com; Tel.: +55-83-998521609

12

13 Abstract: The use of plant fibers as reinforcement in composites with the aim of totally or partially
14 replacing synthetic fibers has received significant attention in the last years. However, one of the
15 disadvantages of the use of these fibers in polymeric composites is associated to the fact that they
16 are hydrophilic, resulting in poor adhesion with most matrices when in the presence of moisture. In
17 addition, another problem encountered is the lower strength of this type of fiber and, as a solution
18 to minimize these problems, the composite can be hybridized by adding layers of natural and
19 synthetic fibers and the use of resin protection along the thickness of the composite. (Lateral
20 protection) to reduce moisture absorption by the laminate. The objective of this work is to obtain
21 composites formed by five layers of reinforcement and terephthalic polyester matrix, one of which
22 is reinforced only with short glass fiber-E blanket, another reinforced only with jute fiber and a
23 third hybrid containing the fibers. Two types of reinforcements with interlayer layers. Afterwards,
24 the loss of mechanical properties was observed when these materials were immersed in distilled
25 water, with and without lateral protection, until reaching saturation. We evaluated parameters
26 such as the influence of configuration type and environmental conditions, such as the amount of
27 water absorption. The obtained results show that the hybrid composite obtained a behavior close to
28 the composite containing only fiberglass, and better than the one containing only jute fiber and that
29 the absorption was smaller in the samples with side protection.

30 Keywords: Polymer composites, fiberglass, jute fiber, moisture absorption.

31

32 1. Introduction
33 There is a worldwide trend towards sustainable alternatives to traditional materials in all
34 sectors of the economy. In this context, there has been a greater demand for materials that met
35 specific characteristics, that is, materials that are economically viable and at the same time meet the
36 new technological and environmental requirements. Thus, there has been an increase in the use of
37 composite materials with the aim of replacing traditional materials [1].
38 In addition to synthetic reinforcements (fiberglass and carbon) [2-4], natural fibers (rami, jute,
39 sisal and curauá) can be used in the fabrication of composite materials. The latter still have the
40 benefit of using a lower cost fiber and when discarded still have the advantage of being less
41 aggressive to the environment [5].
42 Due to the poor mechanical performance of some plant fibers, their union with higher
43 performance (synthetic) fibers can give rise to materials with greater probability of structural
44 application. In hybrid composites two or more types of fibers are used as reinforcements in one or

© 2018 by the author(s). Distributed under a Creative Commons CC BY license.

Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 24 May 2018 doi:10.20944/preprints201805.0342.v1

45 more types of resins. The main idea is to meet certain properties that only one type of fiber and
46 matrix does not meet [6].
47 During the use of a composite, a common problem to be verified is the loss of its mechanical
48 properties with the presence of moisture, being more aggravating in the natural fiber-based
49 composites due to its hydrophilic nature [7-8]. In addition, plant fibers may be susceptible to fungal
50 and bacterial attacks.
51 Thus, this work has the objective of verifying the loss in the mechanical properties of three
52 laminated composites after being saturated in distilled water. One of them was reinforced only with
53 E-glass fiber blanket (MV), another hybrid with E-glass fiber and jute fabric with interlayer layers
54 (HJV) and a third containing only jute fiber fabric (TJ). In addition, it has been found that the use of a
55 side shielding of the samples decreased moisture absorption and loss in mechanical properties.

56 2. Materials and methods

57 2.1. Manufacturing Process

58 For the manufacture of the laminates, Terephthalic polyester resin was used as matrix, with
59 density of 1.30 g/cm³ and viscosity of 310 cP at 25 °C. The catalyst used for the resin curing system
60 was Butanox. As reinforcement material, the E-glass short fiber blanket (5 cm long) was used, with a
61 weight of 450 g/m², the fiber density at 2.54 g/cm³ and a bidirectional jute fabric at a weight of 306
62 g/m2. The composites were manufactured by the manual laminating process, which consists of
63 placing blankets and fiber fabrics on the surface of a mold, followed by the application of resin for
64 impregnation.
65 Three plates of 1.5 m2 each were obtained, in the form of laminar structures, all with 5 layers of
66 reinforcement and polyester matrix. Where one of them contains five layers of E-Glass (MV) Short
67 Fiber Blanket, the other contains five layers of Bi-Directional Jute Fibers (TJ) and the third is a hybrid
68 of three layers of Short Glass Fiber Blanket -E and two layers of two-way jute fabric (HJV) (Figure 1).

69

70 Figure 1. Configuration used in the construction of composite laminates MV, HJV and TJ.

71 It should be noted that, for the uniaxial tensile tests, the bidirectional tissues present with the
72 directions of the fibers always parallel (0°) and perpendicular (90°) to the direction of application of
73 the load. The thicknesses of the composites resulted in approximately 4 mm, 5 mm and 6 mm for the
74 MV, HJV and TJ, respectively. For the mechanical tests, eight tests were carried out for each case and
75 for the water absorption and density tests, five samples were used, totaling 186 tests.
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76 The idealization of these types of laminates is aimed at the application involving high moisture
77 content, such as reservoirs, water and sewage pipes or even in the nautical industry.

78 2.2. Volumetric density and calcination

79 For the determination of the volumetric density of the composite, the standard ASTM D7929
80 was used. Calculations were performed according to Equation (1).

81 (1)

82 In Equation 1, D is the density of the composite, (g/cm3), a is the weight of the dry sample, (g),
83 w is the weight of the yarn partially immersed in water, (g) and b is the weight of the yarn with
84 samples immersed in water, (g).
85 The procedure for obtaining the percentages of fiber, resin and voids was through the
86 calcination test. For this, the test proof bodies of volumetric density were used, where they were
87 pyrolyzed to eliminate part of the resin, and then were placed in the murine-like oven at 750 °C for a
88 period of 40 min. In this way, the volumetric fractions of fiber, resin and voids were obtained.

89 2.3. Uniaxial Traction Test

90 The ASTM D303910 was used to perform this test. For the determination of the mechanical
91 properties of uniaxial traction, eight specimens of each composite were tested and, for each
92 situation, dried and then saturated in distilled water with and without protection of the lateral
93 edges. The test was performed at a speed of 1 mm/min and then the ultimate tensile strength,
94 modulus of elasticity and rupture deformation were determined for the samples before and after
95 immersion of the specimens in the distilled water.

96 2.4. Water Absortion Test

97 The water absorption tests were conducted in distilled water and based on ASTM D57011. For
98 each laminate, five test specimens measuring 25 mm x 76 mm were used.
99 The test specimens were cut, measured and weighed before being immersed in water at
100 ambient temperature. Since absorption is greater at the start of the process, the samples were
101 weighed in the first 12 h and after 24 h measures were taken every week (168 hours).The material
102 was considered saturated, that is, could not absorb more water, when absorption did not exceed the
103 previous measure by 1 % or when the absorbed weight was less than 0.005 g between weighings.
104 It is important to underscore that the tensile and three-point bending tests were conducted in
105 both dry and saturated samples for both laminates.
106 In addition, we analyzed the value of the diffusion coefficient (D) and coefficient of Fick, this
107 parameter is the absorption rate, in this case the speed that the water is absorbed by the material, so
108 that a material with high diffusivity coefficient will absorb large amounts of water quickly,
109 something undesirable in most applications, while a material with a low value of diffusion
110 coefficient takes a long time to absorb water even absorb large quantities at the end of the test.
111 Equation 2 [12] then refers to the calculation of the Fick coefficient (mm2/s).

112 (2)

113 In the Equation 2, D is the coefficient of Fick, h is the mean thickness of sample (mm) mm and the
114 maximum moisture absorbed t2, t1, M2 and M1 are time points (s) and humidity respectively obtained in the
115 linear region (initial) humidity test.
116 From Fick obtaining the coefficient may be constructed to theoretical curve of water absorption (G),
117 represented in Equation 3 [12]. Where t is the time in seconds, and D shows the diffusion coefficient.
Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 24 May 2018 doi:10.20944/preprints201805.0342.v1

118 (3)

119 3. Results and Discussion

120 3.1. Volumetric densities and volumetric percentages of Composites

121 The volumetric densities and fiber percentages of the composites MV, HJV and TJ are shown in
122 Table 1. As expected, the volumetric density value of the glass fiber composite presented the highest
123 value, while the composites with jute fiber presented lower values, due to the density of the jute
124 being smaller than that of the glass fiber.

125 Table 1. Volumetric density of the three composites analyzed.

Configuration Density (g/cm3) Fiber glass Jute fiber

MV 1.51 24% -
HJV 1.37 12% 15%
TJ 1.19 - 26%

126 In addition, it is noticed that the volumetric percentages of the fibers are similar to each other,
127 this is important because it allows to make a comparison between the laminates considering only the
128 fiber used.

129 3.2. Moisture absorption test

130 In order to analyze the moisture absorption in glass fiber blanket (MV) laminates, in fiberglass
131 and jute blanket (HVJ) laminates and in jute fiber (TJ), moisture absorption tests were performed,
132 which are shown in Figures 2 and 3, respectively. By these results we can see that all these materials
133 presented an absorption that follows the law of Fick. This result was found with similar values by
134 other authors [14-16].

135

136 Figure 2. Percent absorption x immersion time - MV.

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137

138 Figure 3. Percent absorption x immersion time. (a) HJV e HJVPL. and (b) TJ and TJPL.

139 Moreover, in the laminates that have jute fiber, in some specimens, the sides were sealed in
140 order to try to decrease the moisture absorption in their thickness, by protecting them laterally (HVPL
141 and TJPL). Figure 3 shows that the use of this technique decreased the water absorption.
142 With the results obtained by the absorption it was possible to obtain the main properties to the
143 absorption of these materials, according to the data presented in Table 2. From these results it is
144 verified that the fiberglass blanket laminate has the lowest maximum absorption value and that the
145 protection Lateral lamellae significantly decreased the diffusivity in the laminates (with a decrease
146 from 2.88.10-6 to 0.545.10-6 for TJ laminate).

147 Table 2. Results obtained in the Moisture Absorption Test.

Maximum Absorption Saturation Time

Material Coefficient of Diffusivity (mm2/s)
(%) (Days

MV 0.41 49 1.51.10-6
HJV 2.48 105 1.24.10-6
HJVPL 1.81 161 0.267.10-6
TJ 5.53 105 2.88.10-6
TJPL 4.36 203 0.545.10-6

148 In addition, the lateral protection significantly increased the saturation time (from 105 to 161
149 days in the HJV material) and the maximum absorption value, and it is recommended for use in any
150 application to reduce the moisture absorption along the time.

151 3.3. Uniaxial Traction Tests

152 In order to evaluate the influence of fiber type and moisture (with and without protection) after
153 saturation, tensile tests were carried out on the materials studied here and their results are presented
154 in table 3, where it was verified that there was a decrease in resistance of 39.33 MPa (percent
155 difference of 40.4%) of the MV laminate for the HJV hybrid laminate, while that decrease was 31.62
156 MPa (54.5% difference percentage) of the HJV for the TJ for the dry state. These results were
157 expected, since the mechanical properties of the jute fiber are inferior to those of the fiberglass.
Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 24 May 2018 doi:10.20944/preprints201805.0342.v1

158 Table 3. Uniaxial Traction Properties of the MV, HJV and TJ Composites in the dry, wet saturated state and
159 HJVPL and TJPL composites in the wet state with lateral protection

Composite materials
Mechanic Proprieties MV HJV TJ
Dry Saturated Dry Saturated HJVPL Dry Saturated TJPL
Last tension (MPa)
97.33 95.05 58.00 55.30 56.89 26.38 19.39 23.43

Modulus of Elasticity (GPa) 2.74 2.31 1.67 1.52 1.66 1.20 0.97 1.02

3.14 3.86 3.13 3.28 2.39 2.16 1.92 1.88

Breaking Deformation (%)

160 In the wet state, the last resistance results are presented in Table 3, there was a decrease of 39.75
161 MPa (percentage difference of 41.82%) of the MV laminate for the HJV hybrid laminate, while that
162 decrease was of 35.91 MPa (percentage difference of 64.94%) from the HJV to the TJ. They obtained
163 similar decrease to those obtained in the dry state.
164 For the lateral protection composites, the final tensile stress values show a decrease of 33.46
165 MPa (58.8% percentage difference) of the HJVPL hybrid laminate for the TJPL laminate. However,
166 when compared the laminate with lateral protection with the unprotected ones, it' is observed that
167 the protection does not bring gain of performance.
168 With respect to the elastic modulus, in Table 3 it is verified that the jute fiber decreases the
169 stiffness of the material. This can be confirmed by analyzing the behavior of the hybrid composite.
170 The percentage difference recorded in the elastic modulus is 39.05% (decrease from 2.74 GPa to 1.67
171 GPa), when comparing MV and HJV, and 28.14% in relation to HJV and TJ (decrease from 1.67 GPa
172 to 1.2 GPa). It is also found that the jute fiber decreases the stiffness of the material when they are
173 wet.
174 In order to better visualize all the results, the bar graph shown in Figure 4 was designed for the
175 resistance of the laminates with the respective dispersions. By this graph, it can be seen that, as
176 already mentioned, the addition of jute fiber decreases the strength of the materials. Even though the
177 resistance decreases in all cases, it decreases within the dispersion margin, except for the TJ, and the
178 use of lateral protection improves the resistance of the TJ. This result demonstrates the importance of
179 hybridization, which in addition to increasing the strength of the composite (relative to TJ), makes it
180 less immune to moisture.

181

182 Figure 4. Comparison of the last tension of the laminates MV, HJV and TJ in the dry and saturated state and
183 with lateral protection
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184 It is also important to note that side-shielded samples were tested in the saturated condition,
185 and that this occurred in a much longer time (50% to 100% of the time) than samples without lateral
186 protection, as shown in Table 2. And yet, they exhibited higher values of resistance. This
187 demonstrates the importance of this procedure in situations of application in great humidity.
188 To analyze the effect of rigidity, the bar graph of Figure 5 was drawn with its respective
189 dispersions. Here, as in the resistance, a decrease in stiffness with the addition of jute fiber and that
190 the humidity has little influence in this factor, staying within the dispersion values, even for the TJ
191 laminate.

192

193 Figure 5. Comparative of the modulus of elasticity of laminates MV, HJV and TJ in the dry and saturated state
194 and with lateral protection.

195 5. Conclusions
196 Based on the presented results, it can be concluded that:
197 - The insertion of jute fiber in the composite makes it lighter due to its low volumetric density.
198 - The use of lateral protection reduced the moisture absorption of all combinations of
199 composites analyzed.
200 - The MV laminates and the HJV hydride composite had similar final tension behavior in the
201 dry and saturated state. The TJ composite, however, had its resistance decreased in the saturated
202 state compared to the dry state.
203 All the laminates had their modulus of elasticity reduced in the saturated state.
204 - The use of lateral protection did not represent significant gains in the analyzed materials,
205 having a little efficiency only in the TJ laminate.
206 - The insertion of the jute fiber significantly decreased the strength and modulus of elasticity.

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