**5. Conclusions**

In the present work, the rehabilitation of damaged pipe was done using CFRP patch made with vacuum bagging process. The optimal parameters for rehabilitating the damaged pipe was derived from the experimental results of "the adhesive bonding of SS plates using CFRP patch made with vacuum bagging process". The parameters considered are vacuum pressure, CFRP/adhesive combination and precuring temperature, bond length and surface texture. Tensile test was considered to evaluate the bond strength of SS plates, and hydrostatic pressure test was considered to evaluate the bond strength of rehabilitated SS pipes. The experimental data was analysed, and the following conclusions were drawn.

	- The viscosity was changed by adding the low viscous nonstructural adhesive. This addition was reducing the bond strength. Hence it was taken as 20% NSA.
	- Heating of adhesive was shown a significant change in the viscosity and its strength. The strength of the pure adhesive and SS-CFRP joint was increased with increase in curing temperature. But it reduces the gel time. At 55°C the minimum curing time is about 2 hrs which is enough time for the present study.
	- 20% NSA + 80% SA mixture heated to 55°C was considered as adhesive conditions for further study.
	- At low vacuum pressures, the compaction pressure on the wetted carbon fibre preform is low. Hence a thick layer of adhesive forms between carbon fibre and SS plates which reduces the bond strength.
	- With 100 mm of Hg vacuum pressure, the obtained joint thickness and load capacity were 4.84 mm and 9.4 kN. With 700 mm of Hg vacuum pressure, the obtained joint thickness and the load capacity were 4.32 mm and 12.6 kN.
	- A maximum of 14.15 kN load capacity was observed with the combination of sandblasted surface with circular cavities occupied at 33% of bonded area, whereas the surface with only sandblasting has shown a load capacity of 12.62 kN which is 12% less.
	- The surface roughness of different prepared samples was also studied, and it was evident that the adhesive bond strength is increased with increase in

**63**

*Overhauling of Steel Pipes Using Vacuum Bagging Processed CFRP Patch*

result in strong and eco-friendly adhesive bonded joint.

The authors have no conflict of interest.

surface roughness. This is because of the increased mechanical interlocking

• The damaged pipe was prepared with different surface textures and rehabilitated with the optimal parameters obtained with the tensile data of the SS plates. A maximum of 3852 ± 50 was achieved with a pipe surface prepared with the combination of sandblasting and circular cavities. It is 6.7 times higher than M-Seal covered cavity and 62.8% higher than the plane surface.

Vacuum bagging process has many advantages in fabricating composite laminates. The proper use of vacuum bagging process in rehabilitation process may

The authors would like to thank "Department of Mechanical Engineering,

National Institute of Technology, Warangal", for providing the facilities.

Syam Kumar Chokka, Beera Satish Ben\* and Kowtha Venkata Sai Srinadh

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

National Institute of Technology, Warangal, India

provided the original work is properly cited.

\*Address all correspondence to: drsatishben@gmail.com

*DOI: http://dx.doi.org/10.5772/intechopen.87074*

with roughness of the surface.

**Acknowledgements**

**Conflict of interest**

**Author details**

surface roughness. This is because of the increased mechanical interlocking with roughness of the surface.

• The damaged pipe was prepared with different surface textures and rehabilitated with the optimal parameters obtained with the tensile data of the SS plates. A maximum of 3852 ± 50 was achieved with a pipe surface prepared with the combination of sandblasting and circular cavities. It is 6.7 times higher than M-Seal covered cavity and 62.8% higher than the plane surface.

Vacuum bagging process has many advantages in fabricating composite laminates. The proper use of vacuum bagging process in rehabilitation process may result in strong and eco-friendly adhesive bonded joint.
