FILAMENT WINDING SIMULATION OF A COMPOSITE OVERWRAPPED PRESSURE VESSEL

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FILAMENT WINDING SIMULATION OF A COMPOSITE OVERWRAPPED PRESSURE VESSEL

FILAMENT WINDING SIMULATION OF A COMPOSITE
OVERWRAPPED PRESSURE VESSEL
Shekhar Kamat,  Xiaofeng Su
Alpha Star Corporation,  
5199 E PCH, #410, Long Beach, CA.90804

Bradley S. Forsyth, Christopher Keddy
Honeywell Technology Solutions, Inc.
Harold D. Beeson
National Aeronautics and Space Administration
NASA Johnson Space Center
White Sands Test Facility
Las Cruces, NM  88004  

Christos Chamis
NASA-Glenn RC, Cleveland, OH
ABSTRACT

Filament winding has proven to be a viable manufacturing technique to produce composite
overwrapped pressure vessels (COPV) for use in space applications. This technique incorporates
winding of composite pre-pregs tapes over a thin metal shell followed by curing. Simulation of
this manufacturing process and subsequent assessment of vessel durability and damage tolerance
(D & DT) is a computationally challenging task, which requires progressive failure analysis
(PFA). This demanding task can be accomplished using GENOA Progressive Failure Analysis
(GENOA-PFA), a tested virtual design/analysis software capable of simulating progressive
failure of composite structures in a variety of situations. A GENOA-PFA module simulating the
manufacturing process for COPVS has resulted in integration of manufacturing, progressive
failure, and probabilistic analysis into a robust software package, GENOA-COBSTRAN.
GENOA-COBSTRAN has been used to simulate the manufacture and pressurization of a
filament wound cylinder consisting of an aluminum 6061-T6 liner overwrapped with graphite-
epoxy composite. The result of the simulation are presented and show 1) the failure pressure, 2)
damage progression and 4) locations and failure modes of failure.
  
KEY WORDS: Composite Materials , Finite Element Analysis (FEM), Filament Winding.
1.INTRODUCTION


Fiber reinforced Composite overwrapped pressure vessels (COPVs) achieve significant weight
reduction by utilizing the high strength and stiffness of composite materials. The GENOA-
COBSTRAN code is designed to carry out analyses  required to efficiently design and analyze
these filament wound pressure vessels, fabricated by over-wrapping thin metal liners with
continuous high strength fibers embedded in resins. Typically the metal liners are made of
lightweight aluminum alloys (tempered to T6) and the composite tape wrappings are made of
high stiffness fibers (eg., carbon, glass and Kevlar) embedded in epoxy resins. The
manufacturing process involves wrapping pre-tensed pre-preg composite tapes of the over a
pressurized metal liner. HOOP, HELICAL and POLAR are the three main wrapping techniques
used. After wrapping, the cylindrical vessels are cured in furnaces at the recommended cure
temperature and then tested for service. The operating pressures of most tanks are of the order of
14-30 MPa, with the burst pressure 1.5 to 3 times the operating pressure.
  
2. COPV AND MATERIAL DESCRIPTION


The aluminum liner used is generally manufactured by impact extrusion or deep drawing and
spinning. A seamless liner without welds or joints is desirable to minimize potential failures
from fatigue or mishandling. The liner material should have sufficiently high strength and
plasticity. Aluminum 6061-T6 is a typical liner material.

High Specific strength and moduli are important considerations in choosing the fibers. Graphite
and Kevlar are the fibers of choice in critical aerospace applications. Most strength critical
aerospace structures are wound with epoxy-based resin systems. The choice of the resin system
depends on its processing characteristics, curing requirements and physical properties of the
resin which affect composite properties. Viscosity and pot life are important processing
considerations. A low viscosity is required for complete wet-out of the strands and removal of
the entrapped air.

3. ANALYSES OF COMPOSITE CYLINDERS


3.1 GENOA-COBSTRAN Analysis  The detailed structural analysis of these composite
cylinders involves understanding the proper material properties and using verified structural
composite analyses.  The  GENOA-COBSTRAN  module undertakes this task using advanced
NASA composite mechanics codes combined with a special module for filament winding. The
filament-winding module duplicates the manufacturing process to generate the correct tape
schedule at each location on the cylinder. The flow-chart is given in fig.1.

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