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ABSTRACT
The present work aims to understand the effect of process induced variation on mechanisms of failure, deformation and damage mechanisms in a model epoxy resin system during machining. Process variations have been introduced for a 5052 Huntsman epoxy resin system by considering three post-cure temperature and cycles, viz., 50°C for 15 h, 80°C for 8 h and 100°C for 4 h. Detailed orthogonal cutting experiments have been carried out at different cutting speeds, rake angles and uncut chip thicknesses. Studies of chip formation characteristics, cutting force signatures and fractography indicate a significant brittle-like behavior with increasing post-cure temperature resulting in discontinuous chips that became more pronounced for a positive rake angle. Concurrently, extensive mechanical characterization under different strain rates and temperatures has been carried out using dynamic mechanical analyzer for the epoxy specimens. In addition, standard tensile tests have also been conducted that indicate a correlation between mechanical properties and post-cure temperature cycles. Results are indicative of a strong correlation between post-cure variations and associated failure, fracture characteristics during machining that can be used as a tool for assessing the in-situ cure characteristics in a composite structure.
KEYWORDS:
Acknowledgments
The current work is partially supported by DST (Department of Science and Technology), Government of India through DSTO/MAS/SMG/1208 grant, which is greatly appreciated. The authors would like to thank Mr. Sagar Kubher, Ph.D. student in the department of Aerospace Engineering, Indian Institute of Science, for his assistance during specimen preparation and mechanical testing.
Nomenclature
| FRP | = | Fiber reinforced plastic |
| PCD | = | Poly-crystalline diamond |
| VARTM | = | Vacuum assisted resin transfer molding |
| DMA | = | Dynamic mechanical analyzer |
| SEM | = | Scanning electron microscopy |
| LCM | = | Liquid composite molding |
| α | = | Rake angle |
| γ | = | Relief angle |
| t | = | Uncut chip thickness |
| V | = | Cutting speed of the tool |
| Fc | = | Cutting force |
| Ft | = | Thrust force |
| Tg | = | Glass transition temperature |
| σ | = | Standard deviation |
| δ | = | Maximum loss tangent |
| μ | = | Mean |
| σY | = | Yield stress |