Interface Strength Modeling in FGMs
Interface failure is the Achilles’ heel of multi-material 3D printed parts. This research developed and validated a multi-scale computational framework to predict and optimize interface strength in Functionally Graded Materials manufactured via Fused Filament Fabrication.
🎯 Research Question
How do gradient transition lengths influence mechanical performance at multi-material interfaces?
Traditional bi-material joints create stress concentrations that lead to premature failure. This study systematically investigated gradient-based solutions to this challenge.
🔬 Experimental Design
Test Configurations
Five interface geometries were fabricated and tested:
| Configuration | Transition Length | Interface Type |
|---|---|---|
| Direct | 0% | Sharp boundary |
| Interlock | — | Mechanical keying |
| Gradient-5 | 5% | Short gradient |
| Gradient-10 | 10% | Medium gradient |
| Gradient-30 | 30% | Extended gradient |
Materials: ABS and Carbon Fiber-Reinforced ABS (CF/ABS)
Testing Standard: ASTM D638 tensile testing protocol
🧠 Computational Framework
A three-scale homogenization approach captured material behavior across length scales:
Scale Hierarchy
Microscale (μm) Mesoscale (mm) Macroscale (cm)
│ │ │
▼ ▼ ▼
┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│ Fiber │ → │ Interbead │ → │ Part-level │
│ Morphology │ │ Voids │ │ FE Analysis │
│ & RVEs │ │ & Layers │ │ │
└─────────────┘ └─────────────┘ └─────────────┘
📊 Key Results
Mechanical Performance Gains
| Metric | Improvement vs. Direct Interface |
|---|---|
| Tensile Strength | +84% |
| Stiffness | +15% |
| Failure Strain | +23% |
Optimal Configuration
The 10-30% gradient length range provided the best balance between:
- Manufacturing complexity
- Strength improvement
- Stiffness retention
🔍 Stress Field Analysis
Finite element simulations revealed that gradient transitions:
- Distributed stress across a larger volume
- Eliminated singularities at material boundaries
- Matched experimental failure locations with 92% accuracy
🚀 Practical Applications
This validated framework enables predictive design of multi-material interfaces for:
- Aerospace: Thermal protection systems with tailored property gradients
- Biomedical: Bone-implant interfaces with reduced stress shielding
- Automotive: Crash-absorbing structures with progressive energy dissipation
📚 Publication
Hasanov, S. (2021). Numerical Modeling and Experimental Characterization of Functionally Graded Materials Manufactured by the Fused Filament Fabrication Process. Doctoral Dissertation, Tennessee Tech University.
View on ProQuest →
🛠️ Tools & Technologies
ANSYS MATLAB Python Abaqus Tensile Testing Microscopy
📸 Stress Field Visualization
Figure: Finite element stress analysis comparing interface configurations. The direct bi-material junction (left) exhibits severe stress concentration at the material boundary—a precursor to delamination failure. The graded transition design (right) distributes stress uniformly across the gradient zone, reducing peak stress by up to 40% and enabling reliable load transfer between dissimilar materials.
