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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1. Overview and limitations Mechanical failure at the interface of Aluminium Continuous fibre (“long-fibre”) Metal Matrix composite (AMMC) with high performance Alumina fibre is discussed with respect to potential benefits to aircraft application, cause of failure, strength, endurance and a method of inspection which may be applicable. The study is limited to combinations of Aluminium LM25, 6061 and primary with the same fibre; made by liquid pressure forming (Bushby’s Patent EP1735119B1 from 2008). Comparisons are drawn against high-strength Aluminium Alloys and a different type of AMMC manufactured using the diffusion bonding process with Silicon-Carbide fibres. Fibres of high stiffness when combined with matrices of a relatively low stiffness seems to result in composite failure which is related to the interface and are superficially characterized, while also considering the effect of elevated and reduced temperature. The influence of fabrication methods upon thermal expansion, creep resistance and fracture toughness given combinations of Al2O3 fibres with Aluminium based matrices are discussed in Delannay and Colin (1993). Further, characterization of basic electrical conductivity behaviour is touched upon in this article. Discussion is limited to uni-directional MMC based upon either of 3 matrix materials - namely primary aluminium, 6061 and LM25 along with Nextel 610 fibre. They are abbreviated here as GD113, GD112 and GD111 respectively, made by liquid state processing. Some comparison is drawn to Aluminium 7010-T7651 and AMMC comprised of Long-fibre SiC with 6061 matrix (abbreviated here as GD222) which is made by Solid-State processing elaborated on by Chawla and Chawla (2013). Only axial failure is examined, and compressive failure not tested. Nomenclature LM25 Commercial grade Aluminium-Silicon alloy similar to A357 and comparable with 6061 TF Fully Heat Treated, heat 4-12 hours, 525⁰C-545⁰C, hot-water quench, age 8-12 hours, 155⁰C-175⁰C, TB7 Solution treated & stabilized; heat 4-12 hours 525⁰C-545⁰C, hot water quench, stabilize at 250⁰C 2-4 hours TE Precipitation treated; Heat for 8-12 hours at 155⁰C-175⁰C and allow to cool in air AMMC Aluminium long-fibre Metal Matrix Composite Ti6Al4v An alpha-beta titanium alloy, that is highly valued for its strength, low density & corrosion resistance. GD1 Liquid State Process based AMMCs GD11 Liquid State Process based AMMCs with Alumina Fibre GD111 AMMC with Alumina fibre and LM25 aluminium alloy matrix GD112 AMMC with Alumina fibre and 6061 aluminium alloy matrix GD113 AMMC with Alumina fibre and 1350 primary aluminium alloy Matrix GD2 Solid State Process based AMMC GD222 AMMC with Silicon Carbide fibre and Primary Aluminium alloy Matrix SiC Silicon Carbide 6061 Aluminium Association UNS designation for A96061 – Al, Mg, Si alloy known for weldability LM25 Commercial grade Al, Si, Mg alloy – designated A356.2 in American system, See BSI (1988) 7010 Aluminium Association designation for Al, Zn, Mg wrought alloy T7651 Solution heat-treated, stress relieved, then stabilized by artificial over-aging RT Room temperature, approximated at 23 ℃ LN2 Liquid Nitrogen, assumed to lie at -196 ℃ 1.1. Relevant definitions and high-level understanding of the interface • Fibres – Continuous fibres made from Al2O3 using the Sol-Gel process by 3M – having high tensile strength and modulus, unless SiC fibres are referred to. The latter are made by Chemical Vapour Deposition. • Matrix – Reinforcement is done by incorporation of a fibre as strong phase into weak phase. Its role is to hold the form of fibres as laid.