The Effects of Winding Angles and Elevated Temperatures on the Crushing Behaviour of Glass Fibre/Epoxy Composite Pipes

S. N. Fitriaha, M. S. Abdul Majidb, R. Daudc, M. Afendid

School of Mechatronic Engineering, Universiti Malaysia Perlis, Malaysia

anfitriah.suhaimi@gmail.com, bshukry@unimap.edu.my, cruslizam@unimap.edu.my, dafendirojan@unimap.edu.my

Keywords: Glass fibre reinforced epoxy; crushing behavior; compression test; elevated temperature; different winding angles.

Abstract. The paper discusses the crushing behavior of various winding angles of glass fibre reinforced

epoxy (GRE) pipes at elevated temperatures. Two different winding angles of composite pipes were

chosen for the study; ± 55°, ± 63°. GRE pipes angled ± 55° and ± 63° are compressed using Universal

Testing Machine (UTM) at room temperature and elevated temperatures of 45°C, 65°C, and 95°C

according to ASTM D695-10 standard. The temperatures were chosen based on the glass transition

temperature (Tg) that was measured earlier. The results show that as the temperature is increased, the

compressive strength significantly degraded. This is due to the change in the properties of the GRE pipe

from a rigid state to a more rubbery state as the composite pipe reached Tg. GRE pipe with winding angle

± 55° show a higher compressive strength compared to ± 63°.

Introduction

Glass fibre/epoxy composites have been widely utilized in engineering applications especially for

the transportation of gas and fluids. In recent years, it has been replacing the use of steel and wood

because of the advantages in its properties such as corrosion resistance, high strength to weight ratio,

competent mechanical properties, and easy to handle. Recent studied have been conducted to determine

the mechanical properties of the GRE pipes which involve tensile, fatigue, impact, and compression tests.

However, this study focuses on the behaviour of the GRE pipes when subjected to uniaxial compressive

loading. Usually, transverse matrix crack, fibre fracture, and delamination are the common damage

modes in composite materials [1].

Studies were also done to determine how different winding angles affect the compressive

behaviour of composite materials. P. D. Soden et. al [2] did a research on the influence of winding angle

on the strength of filament-wound composite tubes. Uniaxial tensile tests were carried out on three

different winding angles of ± 45°, ± 55°, and ± 75°. The results show that lower winding angles yield a

higher axial tensile strength. A. W. Wharmby et. al [3] found that the specimen that shows the highest

stiffness is the lowest angle when comparing three angles of 25°, 45°, and 75°. A study conducted by M.

S. Abdul Majid et. al [4] compared the effect of winding angles on biaxial ultimate elastic wall stress

(UEWS) and concluded that winding angles indeed affect the mechanical properties of the GRE pipes.

As for GRE pipes conditioned with different temperatures, M. S. Abdul Majid et. al [5] did a study on

the behaviour of GRE pipes under hydrostatic and biaxial load conditioned at elevated temperatures. The

results obtained proved that the test temperatures strongly affect the failure of the GRE pipes.

Materials and Experimental Methods

a. Fabrication process of glass fibre reinforced epoxy (GRE) pipes

The wet filament wound process was used to fabricate the composite pipes. The GRE pipes were

produced at Advanced Materials Research Centre (AMREC), SIRIM Kulim High Tech Park. Fibres were

passed through a resin bath to produce resin impregnation. Then, at an angle of ± 55° and ± 63°, the wet

fibre is applied to a mandrel using CNC control filament winding to produce the winding angles. The

dimension of the pipes are about ± 2.5 mm thick and ± 1000 mm in length. Once the resin had dried out,

the pipes were cured for 3 hours at a temperature of 130oC. Lastly, the pipes are left to cool at room

temperature before being removed from the mandrel.

b. Preparation of test specimens

As specified in ASTM D695-10 [6] standard, the GRE pipes were cut into smaller specimens of

± 100 mm in length using a jigsaw cutter. Altogether 8 specimens were prepared to carry out the

experiments with the length of the specimen should be equal to the diameter of the specimen.

c. Differential Scanning Calorimetry (DSC)

To determine the value of the glass transition temperature (Tg) of the GRE pipes, DSC tests were

carried out. Tg is where the specimen changes from rigid state to a more rubbery state. The specimen was

heated from 30oC to 700oC at a rate of 10oC/min. The value of Tg obtained is 66.39oC.

d. Compression tests

Universal Testing Machine (UTM) was used to carry out the uniaxial compression tests at elevated

temperatures ranging from room temperature to 45oC, 65oC, and finally 95oC. The selected temperature

is determined according to the Tg value obtained through DSC process. To observe the failure of the pipes

at various temperatures, the temperatures were set to be below Tg, at Tg, and above Tg. The tests were

carried out at a speed rate of 1.0 ± 0.3 mm/min in accordance with ASTM D695-10 [6] standard. Fig 1

illustrates the uniaxial compression process for the GRE pipes.

Fig 1: GRE pipe subjected to compressive loading

Results and Discussion

The results of the crushing behaviour of the GRE pipes with respect to different winding angles

is represented in the form of stress strain diagram comparing two different winding angles of ± 55o and

± 63o. Fig 2 shows the compressive stress-strain response of the GRE pipes. According to the figures, as

the temperature during compression is increased, the strength of the GRE pipes decrease. Fig 2(a) shows

for winding angle ± 55°, the maximum compressive strength was recorded at 80.45 MPa when the

specimen was crushed at room temperature (RT). As the temperature was elevated to 45oC, 65oC, and

95oC, the strength of the pipes degraded to 41.37 MPa, 10.18 MPa, and 5.71 MPa respectively. Tests at

95oC yields the lowest strength of 5.71 MPa while the highest is at RT. This suggests that a significant

degradation in the compressive strength which is over 90% occurs when the temperatures were elevated.

As for Fig 2(b), observations on test results indicated that the maximum strength of GRE pipes

angled ± 63o yields a value of 37.84 MPa when subjected to compression at RT. This is followed by 45oC

at 10.85 MPa, 4.33 MPa at 65oC and lastly 2.84 MPa at 95oC. The highest compressive strength is

recorded at RT while the lowest is at 95oC. This shows that as the temperatures are elevated, the

composite pipes experienced over 90% drop in compressive strength.

As a comparison between crushing behaviour for GRE pipes angled ± 55o and ± 63o, a higher

compressive strength was yielded from the compression of 55o angled pipes. The strength at RT and 95oC

for ± 55o is 52.97 % and 50.34 % higher compared to that of ± 63o. The results show that composite pipes

at winding angle ± 55° has a higher crushing behavior than ± 63°. As observed, elevated temperatures

reduce the compressive strength of the GRE pipes. The strength begin to decline rapidly as the

temperature reaches Tg and continue to rise above Tg. This is because the composite pipes change from a

rigid state to a rubbery state at Tg. The higher temperatures cause the glass fibres to become more ductile

and the resin matrix to soften hence requiring less compressive strength to deform [5].

(a)

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Fig 2 : Stress strain diagram for crushing of GRE pipes angled (a) 55o and (b) 63o at elevated temperatures

Conclusion

The effect of winding angle and elevated temperature on the crushing behaviour of GRE pipes

were investigated. The results indicated that a lower value of winding angle yields a higher compressive

strength. At elevated temperatures, the pipes significantly degraded from room temperature to higher

temperature due to a change in the properties of the GRE pipes.

Acknowledgement

The authors would like to thank all the fellow researchers involved and also all the staffs of School

of Mechatronic Engineering, UniMAP who had been a great help up to the completion of this study.

References

[1] J. Lundgren and P. Gudmundson, “Moisture absorption in glass- fibre / epoxy laminates with

transverse matrix cracks,” vol. 59, pp. 1983–1991, 1999.

[2] P. D. Soden, R. Kitching, P. C. Tse, Y. Tsavalas, “Influence of winding angle on the strength and

deformation of filament-wound composite tubes subjected to uniaxial and biaxial loads”,

Composite Science and Technologies, col.46, pp. 363-378, 1993.

[3] A. W. Wharmby and F. Ellyin, “Damage growth in constrained angle-ply laminates under cyclic

loading,” Compos. Sci. Technol., vol. 62, no. 9, pp. 1239–1247, Jul. 2002.

[4] M. S. Abdul Majid, M. Afendi, R. Daud, A. G. Gibson, M. Hekman, “Effects of winding angles

in biaxial ultimate elastic wall stress (UEWS) tests of glass fibre reinforced epoxy (GRE)

composite pipes”, Advanced Materials Research, vol. 62, pp. 424-428, 2013. [5] M. S. Abdul Majid, T. A. Assaleh, A. G. Gibson, J. M. Hale, A. Fahrer, C. A. P. Rookus, M

Hekman,”Ultimate elastic wall stress (UEWS) test of glass fibre reinforced epoxy (GRE) pipe”,

Composites: Part A, vol.42, pp. 1500-1508, 2011.

[6] ASTM D695-10. Standard test method for compressive properties of rigid plastics.

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