PERFORMANCE OF 3-D POLAR WEAVE CARBON-CARBON … · Atmosphere, Erosion Rate, Carbon-Carbon...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 3, March 2017, pp. 219–228 Article ID: IJMET_08_03_024 Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=3 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed

PERFORMANCE OF 3-D POLAR WEAVE

CARBON-CARBON COMPOSITES IN HIGH

THERMAL EROSIVE ENVIRONMENT

V. Murali Mohan

Research scholar, Mechanical Engineering, Osmania University, Hyderabad, India

Dr. T.V. Karthikeyan

Research Guide, Mechanical Engineering, Osmania University, Hyderabad, India

Dr. Sriram Venkatesh

Professor, Mechanical Engineering, Osmania University, Hyderabad, India

ABSTRACT

Composite structures are generally made with bi-directional reinforcement either

by filament winding and with continuous fiber or by laying of woven fabric or contour

woven socks. For high temperature Aerospace applications the an-isotropic mechanical

property of bi-directionally reinforced materials poses a design problem as the

mechanical properties in the third direction are dominated by the matrix. Low strength

in the unreinforced regions between the fabric piles is a severe limitation for high

thermal erosive environment. This problem is especially critical in applications

involving high thermal stresses for ballistic Re-entry Nose tips and Solid Rocket motor

throats [1]. The obvious solution is to add fiber reinforcement in the other directions to

make the structure isotropic. This paper gives the complete details of the experimental

3-D cylindrical preforms developed with polar co-ordinates. This paper also explains

the erosive behaviour of 3-D cylindrical preform in Oxy-Acetylene flame testing.

Key words: 3-D Polar Co-Ordinates, 3-D Cylindrical, 3-D Preform, Erosive Atmosphere, Erosion Rate, Carbon-Carbon Composites, Weave Spacings, Nozzle Throats.

Cite this Article: V. Murali Mohan, Dr. T.V. Karthikeyan and Dr. Sriram Venkatesh, Performance of 3-D Polar Weave Carbon-Carbon Composites In High Thermal Erosive Environment, International Journal of Mechanical Engineering and Technology, 8(3), 2017, pp. 219–228. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=3

Performance of 3-D Polar Weave Carbon-Carbon Composites In High Thermal Erosive Environment


1. INTRODUCTION

Multidirectionally reinforced composites have emerged and revolutionised the material technology development, due to their immediate adaptability to withstand all the rigorous thermal loads [2]. Multidirectionally reinforced preform technology provides a mechanism to produce tailored composites to meet directional properties viz. Thermal, mechanical and physical properties of an end item [3]. Preform design and development process has been invented wherein, selective fibre orientations with definite fibre spacings, volume fractions, substrate density and yarn packing efficiencies could be achieved in a structural composite to accommodate the design loads [4]. These 3-D structures overcome the delamination problem associated with 2-D composites.

High temperature metals, refractories and conventional composites could solve the problems to a limited extent and development in this direction has come to almost to a terminal stage. Multidirectionally reinforced carbon-carbon composites have emerged and revolutionised the material technology development, due to their immediate adaptability to withstand all the rigours of thermal environment [5]. Basic research is going on 3-D composites but even today sufficient data is not available to understand these in depth. The aim of the research is to develop the different multidirectional composites, the manufacturing process identification and application [6]. To evaluate the mechanical properties and erosion properties for thermal environments and finally to focus on one of the critical aerospace application where aero-thermal loads are predominant on other hand to develop manufacturing process with low cost and faster production rates.

Applications such as Nose Tips and Heat shields for Re-entry bodies and rocket nozzles have stimulated the development of carbon-carbon composites. These materials retain their strength from frigid cold of space to scorching, heat of re-entry [7]. Due to the superior thermal, mechanical and frictional properties these composites find applications in Aerospace, Defence, Industrial and Medical sectors.

2. EXPERIMENTAL

2.1 3. D POLAR WEAVE

Cylinders, frusta and ogives are woven with yarn reinforcements in the Radial, Axial and Circumferential directions. Finished preforms have continuous yarns in all three directions with Axial yarns oriented along the surface and Radial and circumferential yarns parallel to the base as shown at Figure 1.

Figure 1 3-D Polar Weave

V. Murali Mohan, Dr. T.V.Karthikeyan and Dr. Sriram Venkatesh


2.2. DEVELOPMENT OF 3-D POLAR CARBON FIBER PREFORM

2.2.1 Loom plates: 3.0 mm thick brass plates are drilled with 2.0 mm holes on 9 PCDs, 90 holes are distributed on each PCD at 40. This drilling pattern is followed to accommodate fibre lay up in ‘3’ directions in polar coordinate normally axial, radial and circumferential directions. Two such plates are drilled.

2.2.2. Preform development

Axial set up: The initial set up consists of making network of Carbon Fiber pultruded rods that simulate the longitudinal bundles of the preform. Dia of 1.99 mm Carbon fiber rods are inserted through drilled loom plate whose holes are laid out in such a way as to define the initial Radial and Circumferential weave spacing of the preform.

The ends of the rods rest on the plain plate and the upper part of the rods extend beyond the upper loom plate, where the Circumferential and Radial corridors can be seen between the rods.

Radial and Circumferential weaving

With the help of a hook shaped needles dry Carbon fibers are laid in the Radial direction from preform ID to OD followed by Circumferential lay up between the corridors of the pultruded rods. Figure 2 shows the loom set up and the 3-D polar weaving progress.

Figure 2 Loom setup

2.2.3. Preform details

3-D cylindrical preform is made of TORYA 6K carbon fibre on polar co-ordinates. Final preform size obtained is 150 mm OD, 96 mm ID with 100 mm Height. Ø 2.0 mm carbon fibre pultruded rods are being used as reinforcement in Axial direction. About nine lines with sixty rods per line i.e., 360 rods are used.



Figure 3 3 D cylindrical preform

Table 1 Reinforcement distribution in different directions

S. No Name Axial (A) Circumferential (C) Radial (R)

1 Fiber used T300, 6K T300, 6K T300, 6K

2 Preform configuration 8 4 4 3 No of filaments 48000 24000 24000

4 Reinforcement in each direction

3017 filaments/mm

2100 filaments/mm 2100 filaments/mm

5 Unit cell dimensions 1.946 mm 3.575 mm 4.45 mm 6 Fibre content by % 32.0 % 30.02 % 37.98 %

7 Fibre content by volume 3.594 mm3 3.31124 mm3 4.122 mm3 8 Total fibre volume

occupied - 35.61 % -

9 Total fibre content Vft - 11.392 mm3 -

10 Unit cell volume - 30.96 mm3 -

11 Preform density - 0.6125 gm/cc -

2.3. DENSIFICATION PROCESS OF MULTIDIRECTIONAL SUBSTRATES

The processing of Multidirectional structure into a fully densified Carbon-Carbon composite can be accomplished by various procedures. The use of pitches as matrix precursors in Carbon-Carbon composites is an extension of graphite processing technology. Coal tar pitch as a matrix has a low softening point, low melt viscosity and high coking value. The preform densification process involves impregnation, carbonization and graphitization cycles. High pressure processing and carbonization of coal tar pitch can increase the coke yield from 50% to over 85%. This technique utilizes isostatic pressure to effectively impregnate and densify carbon-carbon composites. Finally the equipment used to achieve densification process is impregnation, carbonizer, graphitizer and Hot isostatic pressure equipment. Density of the final product is aimed to reach 1.86 gm/cc. This is a cyclic process and taken 16 weeks time for each product to reach the desired density.



Figure 4 Densification process of 3-D polar weave c/c composite

When samples are reached the desired density as a Carbon-Carbon composite, processing has completed.

2.4. MATERIAL CHARACTERIZATION

Samples are tested for Tensile and Compressive properties.

2.4.1. Tensile test

Tensile testing of 3-D polar weave c/c composite is carried out as per the ASTM standard. Samples are cut prepared in Axial direction and universal testing machine is used to test the samples. Figure 5 showing the test result of tensile test.

Figure 5 Tensile test for 3-D polar weave c/c composite

2.4.2. Compression test

Samples are cut in Axial, Radial and Circumferential direction as per ASTM standard and subjected to compressive loads. Figure 6 showing the test result of compression test.

Carbon-carbon

composite

Liquid

impregnation

Carbonizer

High pressure

impregnation

HIP

Graphitization

Graphitizer



Figure 6 Compression test for 3-D polar weave c/c composite

2.5. OXY-ACETYLENE FLAME TEST SETUP

Most of the Carbon-Carbon composites used for Aerospace application are tend to withstand high thermal environments where severe aerothermal loads are acting over the component as one of the examples is Rocket Nozzles. Here the criteria in selecting the material are it has to withstand temperature upto 30000C and Fumes travelling at a Mach of more than 1.0. Graphite may be one of the candidate materials for this application, but reinforcement is missing in the bulk graphite. The failure of the graphite is catastrophic in nature and 2-D composites may erode non uniform pattern may lead to lose the mission which is highly critical. In 3-D polar weave, fibers are positioned parallel to flow of the axis and radials are at 900 angle. Circumferential fibres are constructed to take Hoop loads. It is decided to check the erosion rates of the 3-D composite in available Oxy-Acetylene setup as per the ASTM standards i.e., ASTM E285-08.

According to ASTM E285-08 standard, erosion properties of c/c composites were carried out in oxyacetylene torch with a circular specimen cut from the 3-D cylindrical block with a size of 67 X 55 X 12 mm was cut and prepared for flame testing. The erosion tests were carried out under 32000C and the specimen was exposed to oxyacetylene torch as shown in Figure 7. The parameters of the erosion test are shown in Table 2. The inner diameter of the oxyacetylene gun tip was 2 mm and the distance between the gun tip and the specimen was 3.0 mm. The sample was fixed in a 4-jaw chuck as shown in the figure and exposed directly to the flame for

5 min duration. The mass erosion rate was calculated according to the equation R� =∆�

�.

Where ‘Rm’ is the mass erosion rate, ‘Δm’ is the samples mass change before & after erosion and ‘t’ is the erosion time.



Figure 7 Oxyacetylene flame test setup

Table 2 Erosion test parameters of oxyacetylene torch

Flux (L/s) Pressure (MPa) Cold wall Heat flux (W/mm2)

Flow velocity (m/sec)

Nozzle angle (deg) O2 C2H2 O2 C2H2

0.42 0.31 0.4 0.068 8.35 210 17.5

Initial mass of 3-D polar sample was 130 grams and final mass of the sample after test was 120.086 gms. From the test data Δm is measured as 9.914 gms for 5 minutes duration.

Therefore, Rm=0.033 gms/sec is erosion rate of 3-D polar weave carbon-carbon composite.

TEST CONDITIONS

60% oxygen plus 40% of Acetylene gas are used for the test and pressure maintained for oxygen gas was 0.4 MPa and the pressure for acetylene gas was 0.068 MPa.

3. RESULTS AND DISCUSSION

3.1. OXY-ACETYLENE FLAME TEST

It is observed that uniform erosion is seen on the specimen and circumferential and axial layers are eroded in uniform fashion and the maximum depth of eroded zone is 2.56 mm for the test duration of 5 minutes. Figure 8 shows the 3-D polar weave c/ c composite eroded specimen after the oxyacetylene flame test.

Figure 8 Eroded specimen after oxyacetylene flame test



The result of the oxyacetylene flame testing and evolution of Mass erosion rate using the given equation is shown in the Table 3 below.

Table 3 Evolution of Mass erosion rate

Pre-test Mass (gms) Post-test Mass (gms) Mass erosion rate (gm/s) Maximum depth (mm)

130 120.086 0.033 2.56

3.2. MICROSTRUCTURE OF 3-D POLAR WEAVE C/C COMPOSITE

The microstructure of the 3-D polar weave Carbon-Carbon specimen before Oxy-Acetylene test and after test are analyzed by scanning electron microscopy (SEM) JEOL JSM-6610LV equipped with an energy dispersive spectroscopy (EDS). Figure 9 shows the SEM image of 3-D polar weave carbon-carbon specimen shot at 1000X in the Axial view before the flame testing. This image clearly shows the integrity of fibre bundles embedded in the matrix.

Figure 9 SEM of 3-D polar weave c/c composite before testing

Figure 10 shows the morphology of the post-test 3-D polar weave c/c composite test piece. The fibres bundles are denudated and burned into broom like shapes.

Figure 10 Micrograph at 400X of 3-D polar weave c/c composite after testing



Figure 11 shows the micrograph of specimen after testing at 700X parallel to the axial fibers. It explains the erosion in the carbon matrix region is significantly higher than that in the fibre region. This micrograph also showing the eroded fibres oriented parallel to the flow direction. Fig 11 also shows the eroded profile of radial fibers at 700X which are positioned at an angle to the flame. It is seen that the exposure to the flame and highly eroded zone is fibres parallel (Axial) to the flame and it is severe in nature in comparison with axial fibres.

Figure 11 Micrograph of specimen after testing at 700X parallel to the axial fibers

SEM micrographs of the oxyacetylene eroded surface (Figure 8) show that the erosion rate in the carbon matrix region is significantly higher than that in the fibre region. The removal of the matrix leads to the exposure of the outer shell of the carbon fibres. These exposed carbon fibres, especially transversely oriented carbon fibres, are easily attacked by the erosive gases, probably at some structural defects. At the atomic level, the structural integrity of carbon fibres is believed to be better in the core region, with the surface containing a high concentration of edged carbons that are more reactive to erosive gases at high temperature. Erosion of the carbon fibre starts from the outer shell and moves towards the core of the fibre. This phenomenon gives a needle-like shape to the fibres that are transversely oriented to the composite surface and parallel to the flame axis.

4. CONCLUSIONS

3-D polar weave techniques for cylindrical shapes are established. Finer dia Carbon fiber rods are required for fine weave preforms. Different 3-D polar configurations have to be densified, tested and evaluated. Evaluation of mechanical properties is carried for 3-D cylindrical carbon-carbon composite and it is observed that the composite can withstand enough thermo-mechanical loads. For Re-entry nozzle tips, nozzle systems uniform erosion is required, non uniform erosion may lead to losing control over the mission requirement and then by losing vehicle. Steering vehicle requires a shape stable nose cone or shape stable nozzle liner. Uniform erosion is observed on the eroded walls of 3-D polar weave carbon-carbon. Since fibres are in three directions circumferential layers are taken Hoop stresses and Axial fibres are taken loads acting parallel to the flame axis. SEM images taken after erosion explains the perfect erosive pattern seen on the fibres positioned parallel to the flow axis. Fine weave with 3-D polar co-ordinates are highly recommended for solid rocket motor nozzles throats. Manufacturing of large size throats calls large size tooling and larger preform manufacturing systems.



REFERENCES

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PERFORMANCE OF 3-D POLAR WEAVE CARBON-CARBON … · Atmosphere, Erosion Rate, Carbon-Carbon...

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