The most effective procedure requires the measurement of the cooling rate after a heating stage by means of a bank of IR lamps (32 kW) for 5 s. The surface temperature was recorded by a thermographic equipment at one Hz frequency. The test is performed in parallel for all the samples and takes 3 min.
A set of 10 samples have been tested, six times each. Specimens are GFRP tubes: 400 mm long, 40 mm in diameter and 4 mm in thickness. The samples were taken from different production lots and had a different amount of porosity so as shown by SEM observations on the cross section. During different tests, possible causes of error as samples' position, edge effects, uneven heating or deriving from object emissivity, have been checked.
A simplified data processing algorithm based on a differential temperature gives the results shown in fig. 1. All samples are individually evaluated and grouped in three classes: good (#1, #2, #3), acceptable (#6, #7, #8, #9, #10) and rejected (#4, #5).In addition, destructive mechanical and electrical testing methods were applied to the same set of samples. Average results of each group of samples are in agreement with the non destructive evaluation.
 Fig.1 results of TNDE of GFRP cylinders |
Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00
Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:
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