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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locations were probed based upon applied loading pattern to capture ‘damage’ profile of fatigue tested coupons without visual evidence of initiation. Coupons at various levels of exhibited endurance were probed and the trend was found to be applicable across GD11 specimen, however ‘asymptotic’ reading tendency for untested GD113 is more pronounced. Fig. 8(a) and (b) are plots of untested and endured specimen at 1,146,159 cycles, while (c) illustrates probing locations. 2, 3, 6 and 7 were selected based upon resistance offered by material against failure at the hole edge. 1 and 8 lie in proximity to grips, 4 and 5 in the compressive edge. 2 and 7, which are diagonally opposing on the symmetric plane exhibit higher damage than 3 and 6 and the reason for the same is assessed as asymmetry. 4 and 5 do not display a significant damage compared to 1, 3, 6 and 8.

b

a

Fig. 8. (a) Untested coupon (MS/m) ; (b) Tested coupon at 1,146,159 cycles (MS/m); (c) Conductivity probing locations.

5. Inference and discussion Mechanical properties of this type of AMMC are promising, but are pending assessment of load effects, away from the fibre orientation axis and of local variations in fibre-volume fraction. At room temperature, failure is believed to be initiated by shearing of the matrix close to the interface, due to difference in stiffness between the fibre and the matrix. Present application concepts are limited to net-shape structure for local property enhancement. Chemical reaction between the matrix and fibre at high processing or operating temperatures can create a brittle interfacial layer acting as a weak link. Instead of facilitating smooth load transfer, the layer hosts crack initiation. Chemical reaction can also consume the outer fibre, reducing its effective diameter and weakening its intrinsic strength. The fact that Alumina is a poor conductor of electricity may be applied towards developing a method of NDT and, may also be considered towards estimation of the residual life of material applied to service. Acknowledgements The authors are grateful to Dr. Shwe Soe, Associate Professor - University of West of England for guidance towards a better understanding of energy absorbed by material during failure We wish to acknowledge Mr. Fraser Wilson for key technical contributions in the past, that have fructified as the present work. References ASTM, 2017. ASTM D3552‑17: Standard Test Method for Tensile Properties of Fiber Reinforced Metal Matrix Composites, pp. 1–11. BSI, 1988. BS1490: Specification for Aluminium and Aluminium Alloy Ingots and Castings for Engineering Purposes – LM25 Alloy. London. BSI, 2010. BS EN 6072:2010 – Aerospace Series: Metallic Materials – Test Methods – Constant Amplitude Fatigue Testing. 30 Sept 2010. Bushby, R.S., Evans, P.J., et al., 2008. Liquid Pressure Forming. European Patent Office, EP1735119B1, 1 Oct 2008. Chawla, K.K., Chawla, N., 2013. Metal Matrix Composites. 2nd Edition, Chapters 1–4. ISBN 978‑1‑4614‑9547‑5. Delannay, E., Colin, C., 1993. Processing and properties of metal matrix composites reinforced with continuous fibres for the control of thermal expansion, creep resistance and fracture toughness. Journal de Physique IV 03, 1675-1684. Gardiner, G., 2017. Commercialization of CMCs and developments for next‑gen performance. Composites World, 11 Apr 2017.