Fabrication and Experimental Investigation of Composite Pressure Vessel

Abstract

Composite pressure vessels are an important type of high-pressure containers that are widely used in aerospace industries. The pressure vessels develop hoop stresses that are twice the longitudinal stresses. CFRP (Carbon Fiber Reinforced Polymer) composite materials with their higher specific strength and characteristics will result in reduction of weight of the structure when compared with isotropic materials like steel. The present work is aimed in understanding the behaviour of the Composite Pressure Vessel with variation of internal pressure. In this connection, a pressure vessel using CFRP (Carbon Fiber Reinforced Polymer) is fabricated which can hold liquids or gases under pressure and is tested at various pressures. The FEA tool ANSYS 14.5 is used to determine better fiber angle required for liquid storage, when the conventional low carbon steel cylinder is replaced with CFRP Pressure Vessel.

Introduction

I. INTRODUCTION

Starting from the oldest ordinary metals such as copper, cast iron & brass to the recently developed advanced materials like composites and ceramics, engineers have a wide choice for selection of materials required for designing and manufacturing of products for various applications. This has also posed an additional problem of choosing the right material for the right process. Therefore, a wide classification is necessary for simplification and better understanding of the characteristics of the materials.

Materials, based on major characteristics like stiffness, strength, density, and melting temperature can be broadly classified into four main categories as metals, plastics, composites and ceramics.

Each category contains more number of materials with a wide range of properties which results in an overlap of properties with other categories. For example, most common ceramic materials such as silicon carbide (Sic) and alumina (Al2O3) have densities in the range of 3.2 to 3.95 g/cc and overlap with the densities of common metals such as iron (7.8 g/cc), copper (6.8 g/cc), and aluminium (2.7 g/cc). The maximum operating temperature in metals does not degrade the material the way it degrades the plastics and composites. Metals generally tend to temper and age at high temperatures, thus altering the microstructure of the metals. Due to such micro structural changes, modulus and strength values generally drop.

II. EXPERIMENTAL SETUP

The first step for manufacturing the pressure vessel is to prepare a mould of   considerable length taken on which the fiber is to be pasted and cut according to the required shape. Various moulds and moulding processes are used in the manufacturing of the pressure vessel. A mould for pressure vessel is as shown in Fig-1. The releasing agent and then another layer of gel coat are applied on the mould for better surface finish of the extracted mould.

III. FINITE ELEMENT ANAYSIS USING ANSYS

A. Introduction to FE Analysis

Finite element Analysis is a powerful numerical technique for analysis. FEA is used for stress analysis in the area of solid mechanics. In finite element method, a body or structure is  divided into smaller elements called finite elements. The properties of the element are formulated and combined to obtain the solution for the entire body or structure. For a given practical design problem the engineer has to idealize the physical system into a FE model with proper boundary conditions and loads that are acting on the system. Then the discretization of a given body or structure into cells of finite elements is performed and the mathematical model is analyzed for every element and then for complete structure. The various unknown parameters are computed by using known parameters.

B. Steps Involved in ANSYS

1) Preprocessor

All inputs like element selection, real constrain, material properties (young’s modulus, poisons ratio, shear modulus) and meshing of the design is given here. And FE analysis is carried out in the solution.

2) General Post Processor

In post processors the results obtain are

• Deformation
• Mechanical Strain (both longitudinal and hoops strain)
• Inter laminate shear stress and shear stress.

3) Designing in ANSYS 14.5

The pressure vessel can be modeled using CATIA software and can be imported into ANSYS or can be modelled directly in ANSYS. Open the Ansys workbench followed by static structural –model –select any one plane, by using center two point arc and lines commands draw the half sketch with required dimensions. The overview of that sketch is as shown below.

Conclusion

1) It can be observed from the simulation values that the deformation is minimum for CFRP as compared with Kevlar, Glass filled epoxy and Cast Iron grade 20 because of high strength (785 KN-m/kg) of CFRP. 2) It is found that the 900 degree fibre angle is best suited for minimum deformation. 3) The composite pressure vessel which is fabricated is tested using hydrostatic testing is and is found that it can withstand pressure up to 4.5 Mpa. While design pressure deformation starts from 3.2 Mpa. 4) When compared with conventional materials like mild steel, the weight of composite materials will be 20-30% lesser. 5) The pressure vessel with aluminum liners and filament wound procedures can withstand pressure about 70 Mpa and can be used for hydrogen storage.

References

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Copyright

Copyright © 2023 Y. Srinivasa Reddy, Dr. K. Rajendra Prasad, V. Mukesh Reddy. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.