DEVELOPMENT OF A NOL RING TEST TO STUDY GLASS/EPOXY SPECIMENS DEGRADATION AND ITS IMPLEMENTATION ON PERTINENT PRESSURE VESSELS
Keywords:
Glass/Epoxy NOL Rings, Burst pressure, Acoustic emission, Pressure vessels , Mathematical approachAbstract
The use of filament winding techniques for the fabrication of plastics composite structures has grown at a fast pace in recent decades. But the test methods and evaluation techniques have lagged behind the field of applications. Methods have been developed for the evaluation of filament wound composite structures making use of NOL (Naval Ordnance Laboratory) ring test specimens. These methods have all been found of value in making materials comparisons in research and development work and have also served as materials quality control techniques. The internal pressure can be applied to the ring shaped specimens similarly to the burst tests of actual pressure vessels. It is important that the fracture behavior inside of the FRP layers could be observed directly while it is impossible to observe the fracture behavior under the surface of actual pressure vessels. A method of ring fabrication and testing techniques for determination of ring tensile strength have been standardized and are presented herein. Also, in order to demonstrate the advantages of ring burst test, the fracture analysis of Glass/Epoxy NOL Rings under defect free as well as adverse conditions was carried out using AE measurement. Consequently, the effect of degradation in strength of Glass/Epoxy NOL Rings was understood by using Acoustic Emission (AE) technique. Moreover, a mathematical approach is used to predict the failure load of Glass/Epoxy NOL Rings at lower level itself with a reasonable error margin. These ring tests have been oriented towards more realistic lines than tensile test on flat specimens. Due to simplicity and low cost of this testing technique, a number of NOL ring tests can be repeated easily comparing with burst tests of actual pressure vessels.
Downloads
References
ASTM D 2290-04 “Standard Test Method for Apparent Hoop Tensile Strength of Plastic or Reinforced Plastic Pipe by Split Disk Method”.
Sanchez M, Louis S, Bruzek C E, Rozental-Evesque M, Rabaud B and Glucina K (2008), “Development of a ‘NOL ring’ test to study polyethylene pipe degradation”, Proc. of PPXIV conference, Oct. 22 – 24, Budapest, Hungary.
Yu Yunhua, zeng Wei, li Moyu, sui Gang,yang Xiaoping, guo Xiaodong (2009), “Relationship between the moisture absorption and properties of carbon fibre filament-wound NOL rings”, Journal of Acta Materiea Composite Sinica, Vol. 26, 72-78.
Fujishima O, Wakayama S and Kawahara M (1994): “AE Characterization of the Fracture Behavior during Ring Burst Test of FW-FRP Pressure Vessel”, Progress in Acoustic Emission VII, Kishi, T., Ed., The Japan Society for Nondestructive Inspection, Tokyo, 463-468.
Horide A, Wakayama S and Kawahara M (1996), “Acoustic Emission Characteristic during ring Burst Test of FW-FRP Multi-ply Composite”, Non destructive Characterization of Materials VIII, Green, R.T., Jr., Ed., Plenum Press, New York, 641-646.
Horide A, Wakayama S and Kawahara M (1999), “Evaluation of Strength in FW-FRP Composites using Ring Burst Test (Effects of Winding Tension on Fracture Behavior and Strength)”, Transactions of the Japan Society of Mechanical Engineers (A), Vol. 65, 631.
Michael D Lambert, Eric A Clark, Thomas H Fronk (2008), “Mechanical properties of hybrid polymer fiber-reinforced laminates in cryogenic conditions”, Utah State University, Logan UT.
Rozental-Evesque M, Rabaud B, Sanchez M, Louis S and Bruzek C-E (2008), “The NOL Ring test an improved tool for characterising the mechanical degradation of non-failed polyethylene pipe house connections”, Suez-Environnement Cirsee, France.
