Influence of Temperature, Strain Rate, and Condition on the Mechanical Response of an AlSi-PES Abradable

Background

To improve the efficiency and operational stability of aero-engine compressors, abradable liners are used to facilitate reduced clearances between the blade tips and the surrounding casing. However, their properties are highly variable due to sensitivities in the plasma spraying process and complex in-service phenomena such as blade-casing interactions and thermal ageing. The abradable variability makes it difficult to model blade-casing interactions accurately, leading to suboptimal blade geometries and clearances.

Objective

This study addresses the impact of abradable condition on its mechanical behaviour and on the blade-casing interaction response.

Methods

The response and failure behaviour of an aluminium-silicon-polyester abradable under quasi-static (0.01 s\(^{-1}\)) and high-rate (850 s\(^{-1}\)) loading conditions over a range of temperatures and pre-treatments have been characterised. Pre-treatments representative of various points throughout the lifecycle of an abradable were used.

Results

The abradable exhibited sensitivity to strain rate, temperature, and particularly the state of the polyester phase. Ageing the polyester reduced its compliance, increasing the failure stress by up to 10% at high loading rates compared to the as-sprayed material. In the compacted specimens, ageing increased the failure stress by up to 50%, attributed to enhanced thermal stability from increased polyester crystallinity.

Conclusions

A better understanding of abradables and their failure behaviour will improve compressor blade and abradable system design, enabling optimal tip clearances and enhancing overall engine performance. These tests provided an account of condition-specific compressive failure behaviour, beginning to bridge the gap between phenomenological accounts from experimental blade–abradable rub tests and observed abradable response.