Nondestructive testing of composite materials

Nondestructive testing of composite materials

The system, which is now implemented onshore as well as offshore, has been further developed by The Danish Welding Institute to include • a report for...

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The system, which is now implemented onshore as well as offshore, has been further developed by The Danish Welding Institute to include • a report for key areas with high corrosion rates • a report for listing of all component data including automatic calculated minimum allowable wall thicknesses based on various standards, and • a graphical output showing the corrosion pattern as a function of time for quick overlook and management decisions. The programme can be operated with an IBM PC or PS computer or any compatible system. The results from the refinery for the period 1972 to 1982 show. that the accumulated savings versus the total yearly cost of the programme have ranged between 8:1 and 23:1. In addition to the corrosion data, a total of 908 reparable defects were found on 600 km of refinery piping. Approximately 300 of these defects were found in welds. About 50% of these were original weld defects not detected during the' construction period, whereas 50% were erosion/corrosion' damages in the weld roots and in the HAZ-zones.

X-radiography was carried out, In this technique real-time imaging was found to be the most useful method. In order to improve the quality of the real-time image computed image processing was applied. Computed tomography is used for detailed examination of otherwise non-inspectable areas. In spite of the limitations of the medical equipment which is at our disposal, this method is sometimes irreplaceable. Holographic interferometry was applied for tests of bonded structures. Good results were obtained using heating-cooling excitation. Experimental results obtained on elements of aircraft structure are described and the capabilities and limitations of different NDT methods are discussed. ELSCINT 2400 IAI-SPAR-J-S 1 444 00691- 5 BP -40. imm T CI

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Nondestructive testing of composite materials Dr S. G i r s h o v i c h

Israel Aircraft Industry A variety of non-destructive testing techniques are being used at IAI for evaluating the integrity of composite materials and structures.

Fig. 2 Computedtomographic section of a J-sectionspar showing voids in the radius and root areas (courtesy Elscint Corp,)

The most extensively used NDT method is ultrasonics, which has been found to be especially suited for detecting delaminations and other discontinuities in laminates and bondlines. Another widely used method is soft X-radiography. This is frequently used for flaw detection in complex shape parts, and finished structures, eg combinations of laminate, honeycomb and foam adhesive bonding. The potentialities of this method have often been enhanced by the use of X-ray opaque penetrants. When honeycomb is located inside metallic structures Xradiography is inadequate. In this case neutron radiography has been successfully used. For detection of flaws in the radius areas of U-channel spars and in the cross-sections of J, T and I integral ribs, microfocus

Fig, 3 Hologram of a bonded structure showing unbonded areas of 15, 25 and 35 mm diameter (courtesy Soreq Nuclear Research Center)

Determining the quality of bonded structures nondestructively Y. Segal, P. Dickstein and E. Segal

Technion -Israel Institute of Technology, Haifa 32000, Israel

Fig. 1 X-radiograph of a porous graphite-epoxy panel enhanced by opaque penetrant

N D T International December 1988

Adhesive bonding is rapidly becoming an important part of joint technology because of its ability to provide more uniform stress transfer, increased fatigue life and a reduction in structural weight. These characteristics are particularly important in high performance structures using aluminium or composite joints. However, a major limitation on the use of adhesives is the difficulty of accurate determination of bond quality and potential

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