The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes
Traditionally used metals and alloys as constructive materials in process equipment can nowadays be successfully replaced in many cases by non-metallic composite materials. The influence of service solutions on the state of stress and tensile properties in longitudinal and circumferential direction...
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Stamenović, М. Drmanić, S. Putić, S. Medjo, B. 2018-06-18T08:28:05Z 2018-06-18T08:28:05Z 2011 The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes / M. Stamenović, S. Putić, S. Drmanić, M. Rakin, B. Medjo // Фізико-хімічна механіка матеріалів. — 2011. — Т. 47, № 1. — С. 57-64. — Бібліогр.: 11 назв. — англ. 0430-6252 https://nasplib.isofts.kiev.ua/handle/123456789/138128 Traditionally used metals and alloys as constructive materials in process equipment can nowadays be successfully replaced in many cases by non-metallic composite materials. The influence of service solutions on the state of stress and tensile properties in longitudinal and circumferential direction of glass-polyester pipes is studied in this paper. These analyses are of great importance for the use of examined pipes in chemical industry. The pipes were produced by Corporation “Poliester” Priboj. The influence of two solutions, methanol and ammonia, was studied. The samples were treated in solutions for three, seven and ten days. After that, the samples were subjected to tensile testing by the standard procedure. The stresses and strengths were determined in longitudinal direction (testing on flat test specimens) and in circumferential direction (ring test). The analysis of test results, according to the type of solution and period of exposure, was done in comparison with the results obtained by virgin pipes testing (without the influence of the solution). Micromechanical analysis on broken samples helped to determine the influence of the solution on the structure of composite pipe and to find out the models and mechanisms which produced decrease of strength. Композиційні матеріали – перспективні замінники металів та сплавів, які традиційно використовують для виготовлення технологічного обладнання хімічної промисловості. Вивчено вплив розчинів метанолу та аміаку на напруження та механічні властивості склополіефірних труб за їх розтягу в поздовжньому та круговому напрямках. Плоскі та кільцеподібні зразки вирізали із труб та випробовували на розтяг за стандартною методикою. Одержані результати порівнювали з даними для труб у вихідному стані. За допомогою мікромеханічного аналізу зруйнованих зразків встановлено характер впливу розчинів на структуру композиційної труби. Розкрито особливості механізму зниження її міцності. Композиционные материалы – перспективные заменители металлов и сплавов, которые традиционно используют для изготовления технологического оборудования химической промышленности. Изучено влияние растворов метанола и аммиака на напряжение и механические свойства стеклополиэфирных труб при их растяжении в продольном и круговом направлениях. Плоские и кольцевидные образцы вырезали из труб и испытывали на растяжение по стандартной методике. Полученные результаты сравнивали с данными для труб в исходном состоянии. С помощью микромеханического анализа разрушенных образцов установлен характер влияния растворов на структуру композиционной трубы. Раскрыты особенности механизма снижения ее прочности. Acknowledgements. The authors would like to thank to the Corporation “Poliester” Priboj for the glass-polyester pipes. SP, MR and BM acknowledge the support from the Serbian Ministry of Science under the project OI 174004. en Фізико-механічний інститут ім. Г.В. Карпенка НАН України Фізико-хімічна механіка матеріалів The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes Влияние рабочих растворов на механические свойства стеклополиэфирных композитных труб при их растяжении в продольном и круговом направлениях Вплив робочих розчинів на механічні властивості склополіефірних композитних труб за їх розтягу в поздовжньому та круговому напрямках Article published earlier |
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| title |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
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The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes Stamenović, М. Drmanić, S. Putić, S. Medjo, B. |
| title_short |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
| title_full |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
| title_fullStr |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
| title_full_unstemmed |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
| title_sort |
influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes |
| author |
Stamenović, М. Drmanić, S. Putić, S. Medjo, B. |
| author_facet |
Stamenović, М. Drmanić, S. Putić, S. Medjo, B. |
| publishDate |
2011 |
| language |
English |
| container_title |
Фізико-хімічна механіка матеріалів |
| publisher |
Фізико-механічний інститут ім. Г.В. Карпенка НАН України |
| format |
Article |
| title_alt |
Влияние рабочих растворов на механические свойства стеклополиэфирных композитных труб при их растяжении в продольном и круговом направлениях Вплив робочих розчинів на механічні властивості склополіефірних композитних труб за їх розтягу в поздовжньому та круговому напрямках |
| description |
Traditionally used metals and alloys as constructive materials in process equipment can nowadays be successfully replaced in many cases by non-metallic composite materials. The influence of service solutions on the state of stress and tensile properties in longitudinal and circumferential direction of glass-polyester pipes is studied in this paper. These analyses are of great importance for the use of examined pipes in chemical industry. The pipes were produced by Corporation “Poliester” Priboj. The influence of two solutions, methanol and ammonia, was studied. The samples were treated in solutions for three, seven and ten days. After that, the samples were subjected to tensile testing by the standard procedure. The stresses and strengths were determined in longitudinal direction (testing on flat test specimens) and in circumferential direction (ring test). The analysis of test results, according to the type of solution and period of exposure, was done in comparison with the results obtained by virgin pipes testing (without the influence of the solution). Micromechanical analysis on broken samples helped to determine the influence of the solution on the structure of composite pipe and to find out the models and mechanisms which produced decrease of strength.
Композиційні матеріали – перспективні замінники металів та сплавів, які традиційно використовують для виготовлення технологічного обладнання хімічної промисловості. Вивчено вплив розчинів метанолу та аміаку на напруження та механічні властивості склополіефірних труб за їх розтягу в поздовжньому та круговому напрямках. Плоскі та кільцеподібні зразки вирізали із труб та випробовували на розтяг за стандартною методикою. Одержані результати порівнювали з даними для труб у вихідному стані. За допомогою мікромеханічного аналізу зруйнованих зразків встановлено характер впливу розчинів на структуру композиційної труби. Розкрито особливості механізму зниження її міцності.
Композиционные материалы – перспективные заменители металлов и сплавов, которые традиционно используют для изготовления технологического оборудования химической промышленности. Изучено влияние растворов метанола и аммиака на напряжение и механические свойства стеклополиэфирных труб при их растяжении в продольном и круговом направлениях. Плоские и кольцевидные образцы вырезали из труб и испытывали на растяжение по стандартной методике. Полученные результаты сравнивали с данными для труб в исходном состоянии. С помощью микромеханического анализа разрушенных образцов установлен характер влияния растворов на структуру композиционной трубы. Раскрыты особенности механизма снижения ее прочности.
|
| issn |
0430-6252 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/138128 |
| citation_txt |
The influence of service solutions on longitudinal and circumferential tensile properties of glass-polyester composite pipes / M. Stamenović, S. Putić, S. Drmanić, M. Rakin, B. Medjo // Фізико-хімічна механіка матеріалів. — 2011. — Т. 47, № 1. — С. 57-64. — Бібліогр.: 11 назв. — англ. |
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57
Ô³çèêî-õ³ì³÷íà ìåõàí³êà ìàòåð³àë³â. – 2011. – ¹ 1. – Physicochemical Mechanics of Materials
THE INFLUENCE OF SERVICE SOLUTIONS ON LONGITUDINAL
AND CIRCUMFERENTIAL TENSILE PROPERTIES
OF GLASS-POLYESTER COMPOSITE PIPES
M. STAMENOVIĆ 1, S. PUTIĆ 2, S. DRMANIĆ 2, M. RAKIN 2, B. MEDJO 2
1 Belgrade Polytechnic, Serbia;
2 Faculty of Technology and Metallurgy, Belgrade, Serbia
Traditionally used metals and alloys as constructive materials in process equipment can
nowadays be successfully replaced in many cases by non-metallic composite materials.
The influence of service solutions on the state of stress and tensile properties in longitudi-
nal and circumferential direction of glass-polyester pipes is studied in this paper. These
analyses are of great importance for the use of examined pipes in chemical industry. The
pipes were produced by Corporation “Poliester” Priboj. The influence of two solutions,
methanol and ammonia, was studied. The samples were treated in solutions for three,
seven and ten days. After that, the samples were subjected to tensile testing by the stan-
dard procedure. The stresses and strengths were determined in longitudinal direction
(testing on flat test specimens) and in circumferential direction (ring test). The analysis of
test results, according to the type of solution and period of exposure, was done in compari-
son with the results obtained by virgin pipes testing (without the influence of the solution).
Micromechanical analysis on broken samples helped to determine the influence of the
solution on the structure of composite pipe and to find out the models and mechanisms
which produced decrease of strength.
Keywords: glass-polyester composite pipe, tension test, ring test, influence of solution,
micromechanical analysis.
Intensive development of polymer engineering, as well as capabilities of polymers
in combination with other materials to form new, synthetic structures of improved me-
chanical properties, led to a real expansion in use of composite materials, followed by
continuous improvement of technology of their manufacturing and application. Com-
posite materials have a wide range of usage, thanks to their good properties under
external loading, specific mechanisms of cracking and capability for accumulation of
energy, and they pose the greatest competition to the classical construction materials.
The advantages are: relatively small mass, good balance strength/mass and stiffness/
mass, good static and dynamic properties, good resistance to corrosion, simplified fab-
rication and time of assembling.
All stated advantages led to the fact that composite pipes are very much used
today in chemical, building, infrastructure and military industry. An important use of
pipes made of composites glass fibres–polyester resin is in chemical industry. Pipes
made for this usage are, during their exploitation, subjected to the influence of static
and dynamic loading. Considering the conditions of possible exploitation in chemical
industry, the subject of this paper is the determination of the influence of solution, as
fluid which is transported through the glass-polyester composite pipes, on their tensile
properties in longitudinal and circumferential direction.
Different structure of composite pipes causes different distribution of stress, and
the development of failure after the initiation of the first cracks. In the last few decades,
Corresponding author: M. RAKIN, e-mail: marko@tmf.bg.ac.rs
58
many researchers have been conducting these investigations. Special attention was
always given to determination of stress conditions in longitudinal and circumferential
direction. The radial-cut method and ring test give the best results for pipes. The radial-
cut method is a simple, inexpensive and approximate method of determining the resi-
dual stress state in a cylindrical part. In this method the ring is cut in the radial direc-
tion to release the residual stresses. Measurement of the subsequent deformation of the
ring in the circumferential and radial direction gives an indication of the magnitude of
the stresses present prior to the cut. Aleong and Munro [1] used this method to deter-
mine the residual stresses in radially-thick filament-wound composite rings. In their ex-
periments the rings were cut along the radius and the radial and circumferential strains
in the rings were measured using resistive gauges. Aleong and Munro [1] performed
the radial cut method on eight E/XA-S Grafil carbon and three S2-glass fibre-epoxy
matrix composite rings with outside to inside diameter ratios of approximately 1.22 to
1.30. The aim of the study presented in [2] was to characterize the influence of struc-
ture on mechanical performance of cylindrical geometries under various loadings. The
studied specimens were glass-epoxy tubes with a [±55°]6 lay-up. All manufacturing
parameters were kept constant, except for the winding pattern. Quality of fabrication
was assessed by strict monitoring of the geometry and microstructure of the tubes.
Tests carried out on the specimens consisted in progressive repeated loadings, aimed at
characterizing the damage behaviour under different loading conditions. Micro-structu-
ral analysis, mechanical behaviour and damage mechanisms of composite tubes under
pure tensile loading are presented in [3]. Tests were performed on ±55° filament-
wound glass fibre-epoxy resin tubes.
The effects of hydrochloric acid (HCl), sulphuric acid (H2SO4), nitric acid (HNO3)
and phosphoric acid (H3PO4) on the mechanical properties of glass-polyester compo-
site pipes internally lined with C glass were studied in [4]. Specimens cut from the
pipes were immersed for various periods – 30, 60, and 90 days in 20% acid concentra-
tion at room temperature and 100°C. The effects of sulphuric acid concentration and
the sequential lay-up of glass fibre reinforcements on the diffusion behaviour of glass-
epoxy composite laminates were studied in [5]. Experimental results for the direct
effect of an acidic stress environment on the stress intensity factor of woven E-glass
fibre reinforced bisphenol-vinylester resin, woven E-glass fibre reinforced bisphenol-
epoxy resin and woven C-glass fibre reinforced bisphenol-vinylester resin composites
are presented in [6]. The influence of different conditions on the mechanical properties
of coir fibre reinforced polymer composites, as well as glass fibre reinforced polymer
composites have been analyzed and compared in [7]. Degradation was studied in dif-
ferent solutions, like 10% NaOH, 1N HCl, 10% NaCl and water. The effect of these
solutions and water on mechanical properties of the composites was studied in detail.
The deterioration of mechanical properties of the composites by environmental weathe-
ring was also studied.
Experimental procedures. Composite pipes have been fabricated in the lab con-
ditions, by Corporation “Poliester” Priboj. The properties are given in official certifi-
cates from the producers of components of used glass-polyester pipes. The producers
of glass fibres, “OHIS” Skopje and “Vidoe Smilevski-Bato” Gostivar, by their certifi-
cate confirm “E” glass with 1% of alkali (Tables 1 and 2). Thermo-reactive polyester
resin produced by “Color” Medvode was used as matrix. Certificate was given for
“COLPOLY 7510” for the type: UP/SOM- highly reactive, low viscosity polyester on
the basis of ortoftaly acid in standard glycol (Table 3).
The pipes were made by the method “filament winding” with angle of glass fibres
reinforcement [90°]2[±55°]4[90°]4. The specimens for tests (flat specimens and rings)
were cut from the samples of pipes according to the standard dimensions, the flat speci-
mens 250×25(20 gage area)×3.5 mm, and the rings of diameter ∅70×35×3.5 mm (ave-
59
rage values for all tested samples). The cutting was performed on machine type NC-2010
(Nr 95110, Ar 001) using the tools with diamond top and the speed of moving which
reduces the heat in the sample.
Table 1. Structural components
of “E”-glass
Structural component Percentage, %
Silicon (IV) oxide 52…56
Aluminum (III) oxide 12…16
Boron (III) oxide 5…10
Sodium (I) oxide,
Potassium (I) oxide 0…2
Magnesium (II) oxide 0…5
Calcium (II) oxide 16…25
Titan (IV) oxide 0…1.5
Iron (III) oxide 0…0.8
Iron 0…1
Table 2. Physical properties
of “E”-glass fibre
Properties
Specific weight 2.54 g/cm3
Tensile strength 2400 MPa
Modulus of elasticity 73 GPa
Extension 3.3%
Thermal expansion 5⋅10–6 K–1
Thermal conductivity 1 W/mK
Dielectrical constant ξ 6.7
Specific electrical resistance 1014 Ω⋅cm
Moisture absorption at 20°C 0.1%
Table 3. Catalog properties of polyester resin
Properties Specification
Appearance Viscous yellow liquid
Density 1.11…1.21 g/cm3
Viscosity at 25°C 220…320 mPa·s
Specific weight 1.19…1.21 g/cm3
Tensile strength 75…85 MPa
Modulus of elasticity 3.6 GPa
Extension 2…3%
Impact toughness /Charpy/ 10…15 kJ/m2
Some of the tested samples were not exposed to solutions (five test specimens),
while the others were exposed to two types of solutions (three test specimens for each
of the three periods – three, seven and ten days). The pipes were exposed to solutions
on the inner side (they were filled with solutions). From the group of organic solvents
methanol was used (CH3OH, p.a.) as 25% solution; while from the group of non-orga-
nic solvents ammonium hydroxide was chosen (NH4OH, p.a.), as 25% solution too.
These solutions (in the remainder of the text these are denoted as methanol and
ammonium hydroxide) were chosen according to the researches which showed that the
mass of the pipe samples changed significantly by exposing to them [8]. After the
mentioned time of exposure, the process of drying started. Test tubes were dried in the
electrical drying machine at a temperature of 30°C for 2 h.
Testing of flat test specimens was performed on servo-hydraulic testing machine
SCHENCK TREBEL RM 100, and ring test on servo-hydraulic testing machine
INSTRON 1332, using an INSTRON FAST TRACK 80800 controller and hydraulic
jaws. The testing was defined by the standard ASTM D 3039 [9] for flat specimens and
ASTM D 2290 [10] for ring specimens. Loading was registered using a measuring cell
60
with capacity of 100 kN. Displacements were measured by double extensometer
HOTTINGER DD1. During the test, force–elongation (∆P/∆l) diagrams were plotted.
Test results and discussion. Tensile strength Rm (MPa) was calculated according
to Eq. 1 in longitudinal direction for flat test specimens, and according to Eq. 2 for the
rings in circumferential direction:
max
,m l
l
P
R
b d
=
⋅
, (1)
max
, 2m c
c
P
R
b d
=
⋅ ⋅
, (2)
where Pmax (kN) is the maximum applied force; b (mm) is the width of the flat test spe-
cimen; bc (mm) is the width of the ring test specimen; d (mm) is the thickness of the
test specimens (flat specimens or rings) – subscripts l and c stand for longitudinal and
circumferential direction in the remainder of the text.
Modulus of elasticity E (GPa) was calculated by the method of linear regression
from rectilinear parts of the force–elongation (∆P/∆l) curves obtained directly from the
testing machine.
1
l
l
PE
b d
∆σ ∆
= = ⋅
∆ε ∆ε ⋅
; 1
2c
c
PE
b d
∆σ ∆
= = ⋅
∆ε ∆ε ⋅ ⋅
.
According to the period of exposure to solutions, as well as the solution type, ave-
rage obtained results for tensile strength and modulus of elasticity in both directions are
presented in Tables 4 and 5. Comparison of these values in circumferential and longitu-
dinal direction, according to the type of solution and number of days of exposure, are
presented in Fig. 1.
Fig. 1. Comparison of average values of tensile strength (a) and modulus of elasticity (b)
in circumferential and longitudinal direction, according to the solution type and period
of exposure: – circumferential, – longitudinal (methanol);
– circumferential, – longitudinal (ammonium hydroxide).
It can be concluded that there is no progressive decrease of tensile strength with
the number of days for which the samples were exposed to the solutions. For tensile
strength after three days, decrease is 3.8% for longitudinal direction and 10.3% for
circumferential direction with methanol, 9.0% for longitudinal direction and 12.6% for
circumferential direction with ammonium hydroxide. After that a decrease of values
also exists, but it is considerably smaller: 8.0% for seven and 8.7% for ten days in lon-
gitudinal direction and 14.7% and 15.4% in circumferential direction with methanol;
11.8% for seven and 12.6% for ten days in longitudinal direction and 17.0% and 17.7%
in circumferential direction with ammonium hydroxide. From Tables 4 and 5, Fig. 1,
61
and also from previous discussion, it can be concluded that both solutions reduce ten-
sile strength in both directions. When comparing the two solutions, the influence of
ammonium hydroxide on reducing is more prominent. Also the greatest tensile strength
reduction in both cases appeared after the first seven days and after that reduction in
the next three days (up to ten days) decreases: 0.7% in both directions with methanol,
and 0.8% in longitudinal direction and 0.7% in circumferential direction with ammo-
nium hydroxide.
Table 4. Average values of tensile strength and modulus of elasticity
in longitudinal direction
Solution Number
of days
Tensile strength –
average value,
Rm, l, MPa
Change,
%
Modulus of
elasticity – average
value, El, GPa
Change,
%
Without
solution – 147.9 – 19.7 –
3 142.2 3.8 17.8 9.6
7 136.1 8.0 16.5 16.2 Methanol
10 135.0 8.7 16.2 17.8
3 134.6 9.0 16.0 18.8
7 130.5 11.8 15.3 22.3 Ammonium
hydroxide
10 129.3 12.6 15.1 23.4
Table 5. Average values of tensile strength and modulus of elasticity
in circumferential direction
Solution Number
of days
Tensile strength –
average value,
Rm, c, MPa
Change,
%
Modulus of
elasticity – average
value, Ec, GPa
Change,
%
Without
solution – 178.9 – 23.2 –
3 160.5 10.3 19.8 14.7
7 152.5 14.7 18.5 20.3 Methanol
10 151.3 15.4 18.2 21.6
3 156.4 12.6 16.8 27.6
7 148.5 17.0 15.5 33.2 Ammonium
hydroxide
10 147.3 17.7 15.4 33.6
However, both solutions caused greater decrease in values for modulus of elasti-
city, and also a decrease of stiffness. After three days, this decrease is 9.6% for longitu-
dinal direction and 14.7% for circumferential direction with methanol, and 18.8% for
longitudinal direction and 27.6% for circumferential direction with ammonium hydro-
xide. After that, the decrease of values also exists, but it is considerably smaller: 16.2%
for seven and 17.8% for ten days in longitudinal direction and 20.3% and 21.6% in cir-
cumferential direction with methanol; 22.3% for seven and 23.4% for ten days in longi-
tudinal direction and 33.2% and 33.6% in circumferential direction with ammonium
hydroxide. Just like for tensile strength, a decrease of modulus of elasticity (stiffness)
under the influence of both solutions is also evident in this case, with higher reduction
for ammonium hydroxide. Also the greatest tensile strength reduction in both cases
62
appeared after the first seven days, and after that reduction in the next three days (up to
ten days) decreases: 1.6% in longitudinal direction and 1.3% in circumferential direc-
tion with methanol, and 1.1% in longitudinal direction and 0.4% in circumferential
direction with ammonium hydroxide.
Results have shown a slight loss: for the tensile strength it is low, while for the
modulus of elasticity it is somewhat higher. This stands for both directions and solu-
tions, and the explanation are models and mechanisms of cracking which were similar.
Because of that, the analysis of results can be conducted according to the reinforcement
which, on the one hand, gives the material strength and stiffness, and on the other (due
to its specific properties) leads to different models of crack initiation and propagation.
This is very important because of the pipe structure, which produced different distribu-
tion of strains in layers, and fibres were not loaded in the same way.
Fibres that broke earlier (Fig. 2) cau-
sed the disturbance in the zone of the
crack, that is, local shear stresses appeared
causing the fibre pullout mechanism.
Important contribution of shear com-
ponents of strain can be seen from the ob-
tained stress–strain (σ–ε) curves, which
were not linear, unlike the most compo-
sites. With the increase of loading, there
was cracking by fibre-matrix debonding,
and the crack which was initiated by brea-
king of fibres was growing along neigh-
bouring fibres and caused a macrocrack
(Fig. 3).
Fig. 3. Macro-crack SEM micrograph of a flat (a) and of a ring (b) specimen.
The result was local cracking of fibres and whole layers (Fig. 4), but the compo-
site still carried the external load. With the increase of loading, local failures started
spreading, and the final crack appeared with a strong acoustic effect, as a consequence
of simultaneous cracking of many fibres. The fibres were cracked chaotically in all
directions.
Delamination of layers is certainly the following phenomenon of damage for all
tested specimens. The surface of delamination has the appearance which is proper for
the surfaces made under interlaminar shear stress along the surface of contact fibre-
matrix.
Fig. 2. SEM micrograph
of the first broken fibres.
63
Fig. 4. The view of local cracking of fibres and whole layers on ring (a)
and flat (b) specimen.
CONCLUSION
It was established by testing of the flat specimens and rings cut from glass-poly-
ester composite pipes that the exposure to service solutions causes decrease of their
tensile strength and stiffness in longitudinal and circumferential directions. Decrease in
elasticity modulus is more pronounced in comparison with the tensile strength in all
cases; in the circumferential direction, much more severe loss of stiffness is observed
under the influence of ammonium-hydroxide (33.6%; while for methanol this differen-
ce is 21.6%). This represents an unfavourable influence, having in mind that the pipes
are exploited in the elastic loading regime without reaching the tensile strength (con-
trolled by appropriate safety factors).
Decrease of strength and stiffness suggests that absorption of the solution, as well
as dissolving of the polymer matrix in the solution, occurred on the inner surface of the
pipes. In this way, with decrease of quantity of resin there was an increased number of
micro-cracks in pipes and weakening of the fibre-matrix bond where micro-cracks
were initiated and large strain concentration occurred. The loss of resin went from the
inner surface of the pipe, considering that this surface was exposed to solutions. Degra-
dation of the fibre-matrix interface is caused by matrix dehidratation, as well as pene-
tration of the solutions through microcracks into the pipe structure. It is observed that
the fibres were not drastically damaged due to the exposure to solutions. Decrease of
strength and stiffness during the first three days is the most prominent, which suggests
that damage processes are the most intensive during this period.
РЕЗЮМЕ. Композиційні матеріали – перспективні замінники металів та сплавів, які
традиційно використовують для виготовлення технологічного обладнання хімічної про-
мисловості. Вивчено вплив розчинів метанолу та аміаку на напруження та механічні влас-
тивості склополіефірних труб за їх розтягу в поздовжньому та круговому напрямках.
Плоскі та кільцеподібні зразки вирізали із труб та випробовували на розтяг за стандарт-
ною методикою. Одержані результати порівнювали з даними для труб у вихідному стані.
За допомогою мікромеханічного аналізу зруйнованих зразків встановлено характер впли-
ву розчинів на структуру композиційної труби. Розкрито особливості механізму зниження
її міцності.
РЕЗЮМЕ. Композиционные материалы – перспективные заменители металлов и
сплавов, которые традиционно используют для изготовления технологического оборудо-
вания химической промышленности. Изучено влияние растворов метанола и аммиака на
напряжение и механические свойства стеклополиэфирных труб при их растяжении в про-
дольном и круговом направлениях. Плоские и кольцевидные образцы вырезали из труб и
испытывали на растяжение по стандартной методике. Полученные результаты сравнивали
64
с данными для труб в исходном состоянии. С помощью микромеханического анализа раз-
рушенных образцов установлен характер влияния растворов на структуру композицион-
ной трубы. Раскрыты особенности механизма снижения ее прочности.
Acknowledgements. The authors would like to thank to the Corporation
“Poliester” Priboj for the glass-polyester pipes. SP, MR and BM acknowledge the
support from the Serbian Ministry of Science under the project OI 174004.
1. Aleong C. and Munro M. Evaluation of radial-cut method for determining residual strains in
fiber composite rings // Experimental Techniques. – 1991. – 15, № 1. – P. 55–58.
2. Rousseaua J., Perreux D., and Verdiere N. The influence of winding patterns on the damage
behaviour of filament-wound pipes // Composites Scien. and Technol. – 1999. – 59, № 9.
– P. 1439–1449.
3. Bai L., Seeleuthner P., and Bompard P. Mechanical behaviour of ±55° filament-wound
glass-fibre/epoxy-resin tubes: I. Micro-structural analyses, mechanical behaviour and da-
mage mechanisms of composite tubes under pure tensile loading, pure internal pressure, and
combined loading // Ibid. – 1997. – 57, № 2. – P. 141–153.
4. Mahmoud K. M. and Tantawi S. H. Effect of strong acids on mechanical properties of glass/
polyester grp pipe at normal and high temperatures // Polymer-Plastics Technology and
Engn. – 2003. – 42, № 4. – P. 677–688.
5. Pai R., Kamath M. S., and Rao R. M. V. G. K. Acid resistance of glass fiber composites with
different layup sequencing. Part I – diffusion studies // J. Reinforced Plastics and Compo-
sites. – 1997. – 16, № 11. – P. 1002–1012.
6. Hiroyuki K. and Srivastava V. K. The effect of an acidic stress environment on the stress-
intensity factor for GRP laminates // Composites Scie. and Technol. –2001. – 61, № 8.
– P. 1109–1114.
7. Degradation studies of coir fiber/polyester and glass fiber/polyester composites under diffe-
rent conditions / K. Sindhu, K. Joseph, J. M. Joseph, T. V. Mathew // J. Reinforced Plastics
and Composites. – 2007. – 26, № 15. – P. 1571–1585.
8. Jelić M. Acid and alkali influence on strength and stiffness glass-polyester composite pipes,
Final exam work. – Faculty of Technology and Metallurgy, University of Belgrade, 2009.
9. ASTM D 3039-00, Standard test method for tensile properties of fiber-resin composites
/ Annual book of ASTM standards. – 2000.
10. ASTM D 2290-00, Standard test method for apparent hoop tensile strength of plastic or
reinforced plastic pipe by split disk method // Annual book of ASTM standards. – 2000.
11. Stamenović M., Putić S., Rakin M., Medjo B. and Čikara D. Effect of alkaline and acidic
solutions on the tensile properties of glass-polyester pipes // Materials & Design. – 2011.
– 32, № 4. – P. 2456–2461.
Received 27.11.2009
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