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

312 4

2. Observations related to mechanical failure Mechanical and thermal residual stresses at the interface are associated with the nature of failure, as interpreted from Kyle-Henney et al. (2019). A typical tensile failure of GD1 specimen appears ductile with classical ‘cup and cone’ features with little topical evidence of brittle failure at the cross section of failure. Failure is initiated at the interface, but propagated through the matrix prior to overload across fibres owing to the resultant asymmetric load during the process of failure. Typical failure is comparable with that of Aluminium-Lithium specimen, which is depicted as part of Fig. 2(a) and 2(b) below. Fig. 3(a) shows randomly orientated fibres with uneven spacing across a 1.24 mm section image. Testing discussed in this section was carried out at Room Temperature (23 ℃ ).

Fig. 2. (a) GD1 tensile failure cross-section; (b) Lateral view of Aluminium-Lithium tensile failure cross-section.

In Fig. 3(b) GD222 on the other hand clearly shows cells, made by foil-fibre process. While ductility is visible along the fracture lines of foils, the cross section itself has failed brittle, with SiC fibres also being ceramic.

Fig. 3. (a) GD11 cross-sectional image revealing randomly orientated fibres (b) GD222 cells made by foil-fibre process.

With GD11, fractures are seen to be generally ductile with some local brittleness. The Fibre tends to ‘pull-out’ but appears brittle upon failure. The matrix tends to elongate and exhibit a tendency to reduce in cross-section for GD222. The Fatigue failure of GD11 is seen to be similar to a tensile failure. However, cracks were seen to initiate at the peak stress concentration point at 3 O’clock of the T-type open hole specimen by BSI (2010) and grow along the fibre. Failure was not seen across the net section as would be expected in homogeneous alloy specimen.