Composite Pressure Vessels

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Composite Pressure Vessels
Rao Yarrapragada K.s.s1, R.krishna Mohan2, B.vijay Kiran3
1,2,3 Associate Professor, Mechanical Department, B.V.C College of Engineering, Andhra Pradesh, India,
[email protected], [email protected], [email protected]
Abstract
Cylindrical pressure vessels are widely used for commercial, under water vehicles and in aerospace applications. At present the outer
shells of the pressure vessels are made up of conventional metals like steels and aluminum alloys. The payload performance/ speed/
operating range depends upon the weight. The lower the weight the better the performance, one way of reducing the weight is by
reducing the weight of the shell structure. The use of composite materials improves the performance of the vessel and offers a
significant amount of material savings. Moreover, the stacking sequence is very crucial to the strength of the composite material. This
Project involves various objective functions such as stiffness, buckling load and Weight at each level of optimization. Usually
composite pressure vessels are designed for minimum mass under strength constraints. A graphical analysis is presented to find
optimum fiber orientation for given layer thicknesses. In the present work, an analytical model is developed for the Prediction of the
minimum buckling load with / without stiffener composite shell of continuous angle ply laminas (±45°,±55°,±65°,±75°,±85°) for
investigation. Comparisons are made for two different approaches i.e. the finite element model and the theoretical model. A 3-D finite
element analysis is built using ANSYS-12.0 version software into consideration, for static and buckling analysis on the pressure
vessel.
Index Terms: Composite material, Shells, Fiber orientation, Layer thickness, Stiffeners, Critical Pressure and Buckling
CONCLUSION
[1].The Lamina stacking sequence is appropriate which is free
from extension – bending, coupling which reduces the
effective stiffness of the lamina, since the laminates are
symmetric.
[2].Appropriate number of plies needed in each orientation
and thickness of the shell is safe from static and buckling
analysis is concerned. The comparison plots obtain
desired results for stresses and deformations with lamina
orientations for the chosen composite materials.
[3]. The chosen fiber volume fraction Vf = 0.65 and Vm =
0.35 is acceptable to the present FRP shell working at 3
Mpa internal (Air) pressure.
[4].The fiber orientation ±55° for glass epoxy and ±65°angle
for carbon and aramid epoxy is correct which optimum
value is. From the finite element analysis report the
maximum stress obtained in each lamina (for ±55, ±65
degrees winding angle) is less than the allowable working
Strength of the FRP lamina. So shell design is safe.
[5].Numerical calculations, Tables and plots obtained for
critical pressures supports the comparisons of buckling
pressures.
[6].The factor of Safety 3 taken is sufficient for the fiber
reinforced Composite material to overcome material
design and manufacturing defects. The average critical
buckling pressure was obtained from finite element
analysis report is 4.0684N/mm2 which is more than the
maximum working pressure 3N/mm2. Hence the buckling
load factor is greater than the unity. Hence the design is
safe.
[7].Comparison of stiffened and unstiffened composite shell
by both theoretically and analytically, that Analyses
supports the stiffened cylinder has more buckling
resistance than that of the unstiffened one.
[8]. Increase in shell thickness is shown to increase the
buckling resistance of the composite shell. The objective
of the analysis and theoretical report shows that fiber
reinforced composite shell can minimize the weight of the
structure.
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