Impact Toughness of Notched Composite Material Jute/polyester
Djeghader Djamel1,2, Redjel Bachir1
1
Civil Engineering department, Faculty of Engineering, University of Badji Mokhtar, BP 12, Annaba,
Algeria
2
Civil Engineering Department, Faculty of Sciences and Technology, University of Mes Saddik Ben Yahia,
BP 98, Jijel, Algeria
djameldjeghader@yahoo.fr
Abstract—In recent years, the use of composite materials reinforced with natural fibers has been the subject
of several studies to provide a possible replacement of ceramic reinforced in composite material. They are
renewed, recyclable, less abrasive and lightweight.In this study, Impact Charpy tests were carried out on
prismatic samples with lateral notches of different depths of a polyester matrix composite material,
reinforced with three layers of bidirectional jute fibers corresponding to a rate of 40%. Three distances
between supports were tested: 40mm, 60mm and 70mm. The tests were performed in 3 points bending with
an impact velocity of 3,85m / s and a pendulum of 7,5 joules. The Williams method based on the principles
of linear elastic fracture mechanics was used to interpret these results and yielded an estimate of the fracture
energy and toughness GIC intrinsic parameter of this material from the total energy U dissipated during
impact. The Impact energy U measurement results according to BDф for all notched specimens tested for
the three distances between support 3 used are characterized by a high dispersion of data points around the
linear regression line. This dispersion characteristic of composite materials is a consequence mainly of the
heterogeneity of the material in the path of the cracking and of the dispersion of the mechanical test itself.
The impact toughness GIC decreases with increasing the distance between supports.
Keywords-impact toughness; jute; polyester; Charpy test.
INTRODUCTION
The composite materials in polymer matrix reinforced with natural fibers are receiving more attention in
both academia and various industries. Jute fiber is one of the best natural fibers used in the mass-composite
materials industry, due to its properties and its availability. This fiber has high specific properties, a less
abrasive behavior of the processing equipment and good dimensional stability. Thus, composite materials
reinforced with jute fiber can be employed as an alternative to replace those reinforced with glass fiber in
many applications that do not require very high impact [1]. Many works have been published in recent years
on the development and characterization of static and fatigue of composite materials reinforced with natural
fibers, but their impact behavior remains little studied [2-3-4]. Amanda and all [5] shows that the
incorporation jute fabric in the polyethylene resin completely changes the characteristics of fracture of these
materials and increases their resistance to impact. Rana et all [6] shows that there are an increase of the
impact energy of a composite material reinforced with short jute fibers and polypropylene matrix with
increasing percentage of jute fibers. This increase in impact resistance is not significant beyond a rate of
50%. Wambua and all [7] examining and comparing the mechanical properties of various composite
materials reinforced polypropylene matrix with natural fibers such as sisal, kenaf, hemp, jute and coconut
fibers, show that the latter displayed a low impact resistance. Another comparison was made with the
corresponding properties of composite materials based on polypropylene matrix reinforced by glass mats.
I.
Composites with natural fibers examined show a low impact strength unlike fiber composites hemp and
sisal which exhibit comparable resistance to the composite materials reinforced with glass fibers. The specific
properties of the natural fibers composite materials are sometimes better than those of composites, Achouri
and all [8] using the concepts of fracture mechanics to characterize in impact test of composite materials
perlon -polyester for orthopedic use and glass-carbon-polyester show that the impact test is very depressive in
its results but remains a fast evaluation of toughness parameters of composite materials for their
classification. Thus, carbon-composite perlon- polyester has better resistance to cracking in the glassdynamic perlon-polyester composite. The subject of this work is to interpret the results of the impact tests on
notched specimens of a bidirectional composite material using the Williams method based on the principles
of linear elastic fracture mechanics.
METHODES AND TECHNICAL
The material used in this study was a composite polyester matrix is recessed by three layers of
bidirectional jute fiber. Specimens used in the impact Charpy test are rectangular, 10mm wide and 4mm thick
on average, type lateral notch SEN (single edge notch). These test pieces were cut to plates of 300x210 mm2
and notched in the middle, at different depths as showed in Figure 1. A pre notching is performed first using
a special saw then tapping is continued with a rigid blade to have an acute form of the crack tip. The lengths
of notches are included in the ratio 0.2 < a/D <0.6, a and D are the length of notch and the width of the
specimen (Fig 1).
II.
Fig 1. Specimen used impact Charpy test
Three distances between support used in our érude (Table1) 40mm, 60mm, 70mm
TABLE 1
SPECIMEN DIMENSIONS JUTE/POLYESTER
Jute/polyester
55 ±0.2
10±0.2
4±0.2
Distance
between
support
L (mm)
≈ 40
70 ±0.2
10±0.2
4±0.2
≈ 60
80 ±0.2
10±0.2
4±0.2
≈ 70
Length l Width D Thickness B
(mm)
(mm)
(mm)
The tests were carried out using a Charpy impact machine with pendulum type Zwick 5113. The flip
angle of the unit is 160° and the impact velocity is 3.85 m / s. The pendulum used in the case of this
materials is 7.5 joules (Fig 2).
Williams method based on the principles of linear elastic fracture mechanics was used to interpret the
results of impact tests on notched specimens [9-10-11]. This method provides an estimate of energy or
toughness GIC of the total dissipated energy during the impact U according to the equation:
U = GIC. B.D.ф
(1)
B and D are respectively the thickness and the width of the specimen and ф is a calibration factor which
depends on the specimen geometry and which was tabulated by Williams for different lengths of notch and
for various ratios L / D. And recording the energy lost by the pendulum at the time of impact for each notch
covered a diagram U = f (BDф) gives a straight line whose slope measurement GIC.
Fig. 2. Charpy impact machine Zwick / Roell
RESULTS AND DISCUSSION
The graphical representation of the measurement points of the energy lost by the total rupture U hammer
surface function cracks ruptured to three distances between supports used are shown in Figs 3, 4 and 5
III.
0,3
GIC = 5,04 KJ/m2
Cr = 0,64
Imacct energy U (J)
0,25
0,2
0,15
0,1
0,05
0
0
10
BDΦ (mm2)
20
30
Fig.3. Total fracture energy based on damage surfaces BDф: L = 40mm
The dispersion of experimental points around linear regression lines is important in all cases tested as
indicated by the correlation coefficients calculated which are much lower than 1. This dispersion also
characteristic of composite materials is the result of heterogeneity especially material on the way of
cracking of the manufacturing method of the notches and the dispersion of the mechanical test itself.
Fig.4. Total fracture energy based on damage surfaces BDф: L = 60mm
The results show that the increase in total energy to break with an increase in damage surfaces is
reflected by the fact that the breaking is a phenomenon energy consumer, therefore increasing broken
surfaces requires more fracture energy important.
Fig. 5. Total fracture energy based on damage surfaces BDф: L = 70mm
The linear regression for all distances between supports 40mm, 60mm and 70mm is provided with
correlation coefficients well below 1, indicating a high dispersion of data points around the linear regression
line. This dispersion is a characteristic of heterogeneous materials and is the result primarily of the
heterogeneity of the material on the way of cracking of the manufacturing method of the notches so that the
dispersion of the mechanical test itself. The presence of defects during manufacture of the test pieces is also
a parameter favoring the measurement variability. Indeed, the distribution of jute fiber content in the
polyester matrix and their orientation is not uniform within the volume of the material, which causes the
often tortuous break paths that do not necessarily follow the direction and the plan the initial cut and that are
different from one specimen to another.
The measurement results of the dynamic toughness as a function of the distance between support 3 point
bending are shown in the histogram in Figure 6 for all specimens tested. These results show that the effect of
the distance between support for jute fiber material is large compared with that on other composite materials
such as polyester glass for example. Indeed the impact toughness GIC decreases with increasing the distance
between supports.
CONCLUSION
The specimens tested is characterized by a brittle fracture mode by the presence of defects due to the
manufacturing method of the material
A dispersion of the measurement results of the fracture toughness by using the Williams method to
interpret the impact Charpy test. This is mainly due to the heterogeneity of the material. The dynamic
impact toughness jute-polyester composite materials decreases with increasing distance between supports 3point bending.
IV.
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