Nirmal Sigamani,
Zoubeida Ounaies,
Ramesh Talreja,
- Research Scholar, Department of Mechanical Engineering, Pennsylvania State University, State College,, Pennsylvania State, USA
- Professor, Department of Mechanical Engineering, Pennsylvania State University, State College,, Pennsylvania State, USA
- Professor, Department of Aerospace Engineering and Material Science & Engineering, Texas A&M University, College Station, TX, 77843, USA., Pennsylvania State, USA
Abstract
Thin polyurethane layers have been widely used as erosion-resistant coatings on helicopter rotor blades such as UH-60 Black Hawk and Eurocopter SA 315. Published research has mainly focused on empirical studies that relate the mechanical properties such as rebound resilience and hardness of polyurethane to solid particle erosion resistance. However, polyurethane possesses phase mixing at multiple scales and thus sand particle erosion resistance depends also on the microstructure and the phase mixing. Hence, it is very important to carry out detailed investigations to understand the stepby- step mechanism of erosion and how it relates to the polyurethane micro, meso, and macrostructure. This study carries out systematic investigations on multiple scales using Fourier Transform Infrared Spectroscopy (FTIR) in the micro scale, Differential Scanning Calorimetry (DSC) in the meso scale and Scanning Electron Microscopy (SEM) in the macro scale are performed to understand the step-by-step mechanism of erosion and how it is affected by the polyurethane microstructure. The comparison of FTIR results on pre-eroded and eroded films reveal the removal of macromolecular bonds corresponding to soft segments in the micro scale. The reduction of the crystalline portion of the soft segment observed from DSC results supports the FTIR findings. SEM images of the eroded specimens are used to correlate the sequence of the damage due to erosion. The observations reveal that after initial ductile deformation of the soft segments on the surface, brittle cracks are formed on the hard segments. The increased exposure to sand particles leads to formation of fragments containing mainly soft segments with cracks in the hard segments propagating in a brittle manner. As exposure increases, cracks intersect and material on the surface gets removed. The removed material mainly contains soft segments, as revealed by the FTIR and DSC results.
Keywords: FTIR analysis, microstructure–property relationship, polyurethane erosion, phase mixing, solid particle erosion
[This article belongs to Journal of Thin Films, Coating Science Technology & Application ]
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Journal of Thin Films, Coating Science Technology & Application
| Volume | 13 | |
| Issue | 01 | |
| Received | 26/11/2025 | |
| Accepted | 17/12/2025 | |
| Published | 25/01/2026 | |
| Publication Time | 60 Days |