PSI - Issue 82

Mr. Parthasarathy Iyengar et al. / Procedia Structural Integrity 82 (2026) 309–316 P. Iyengar, J. Mardaras, S. Kyle-Henney / Structural Integrity Procedia 00 (2026) 000–000

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T-test ‘open-hole’ specimen as per EN 6072 by BSI (2010) was applied and a small test programme was initiated following the confidence found by the endurance displayed by test of the first specimen at 4844588 cycles at applied gross stress of 123 MPa to GD111. GD113 exhibited 2 orders of magnitude improvement over 7010-T7651 [from data corroborated with MMPDS-14 (2019)]. It is also believed that removal of the peripheral matrix layer of GD11 by precision surface machining post liquid pressure forming, influences towards fatigue life improvement. Indicative S-N curves plotted from testing of specimen at several stress levels are summarized in Fig. 6(a).

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Fig. 6. (a) S-N curves of tested AMMC specimen; (b) Failed ‘TF’ specimen & micrograph. However, when subjected to heat treatment, nominally to “TF” condition, a GD111 specimen failed at 463 cycles. Failure analysis of specimen revealed the penetration of coarse Si rich phases into the matrix replacing severally, the more globular precipitation. Matrix channels of high width were created, encouraging local failure at the strength of the matrix and propagation within the region. Si rich phases as seen in Fig. 6(b) above, are believed to imply heterogeneous distribution of properties across a section, comparable with Al-Si morphology from Polmear et al. (2017). Metal rich channels are known to be a function of pressure versus preheat temperature and may be deferred through tweaks to the manufacturing process. Under elevated temperature at 70℃, a tensile strength knockdown of 40% to 50% was observed upon GD112, GD113 and GD222 with no significant change to stress-strain characteristic from RT. For low temperature testing with LN2, while no notable change was observed upon the UTS, absorbable energy was measured to be lower as shown in load-extension plots as Fig. 7(a) and (b).

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Fig. 7. (a) Load-extension at RT; (b) Load-extension of specimen cooled by LN2.

4. Inspection for AMMC with Nextel 610 Long fibre The fact that Alumina is a poor conductor of electricity is likely to result in a different value of conductivity from a cross-section of AMMC with damaged Nextel 610 Long fibre was applied towards characterization. Fixed point