Process-induced defects
Quantify how tow gaps, compaction pressure, cure cycles, squeeze flow, and resin bleed-out create resin-rich pockets, ply sinking, and non-uniform laminate morphology.
Composite manufacturing research
Ahmad Ravangard
I am a mechanical engineering Ph.D. researcher at Old Dominion University studying how automated fiber placement creates defects in carbon-fiber composites, and how those defects can be measured, modeled, and reduced. My work connects microscopy, DIC, micro-CT, tensile testing, finite-element simulation, and data-driven analysis to move from manufacturing process to structural performance.
Research focus
From AFP process defects to reliable composite structures.
I study the chain that links placement, compaction, resin flow, cure, morphology, and failure. The goal is to understand where tow gaps, resin-rich regions, and fiber waviness come from, then turn that understanding into mitigation strategies that are practical for aerospace-grade composite manufacturing.
- Materials
- Carbon-fiber/epoxy laminates, PEI/PPS veils, platelet-molded composites
- Measurements
- DIC, microscopy/fractography, micro-CT, tensile testing, profilometry, rheometry, DMA, DSC
- Models
- FEA, CFD, compaction, cure kinetics, resin flow, progressive failure, machine learning
Research priorities
A process-to-performance view of composites.
Defect mitigation materials
Evaluate selective PEI/PPS thermoplastic veil placement as a way to reduce fiber waviness, interrupt resin-rich channels, and improve laminate uniformity.
Process-performance modeling
Build finite-element and flow models for compaction, resin transport, cure kinetics, structural response, and progressive failure, then calibrate them against experiments.
Data-driven microstructure analysis
Use image analysis, computer vision, and machine learning to connect microstructure with process history, morphology, and measured mechanical performance.
Methods
A mixed experimental and computational toolkit.
Manufacturing
01
Composite processing
AFP-related process behavior, tow-gap formation, resin flow, compaction, cure kinetics, and morphology control in composite laminates.
Simulation
02
Process and failure modeling
Finite-element and flow simulation for compaction, resin transport, structural response, and progressive failure in non-uniform laminates.
Testing
03
Full-field characterization
Lab validation with DIC, microscopy, micro-CT, profilometry, thermal analysis, and mechanical testing.
Data and code
04
Scientific computing and AI
Python, MATLAB, numerical methods, image analysis, and machine-learning workflows for simulation, reconstruction, and research automation.
Selected work
Case studies across composites, flow, and numerical methods.
AFP composites
Mitigating out-of-plane fiber waviness with thermoplastic veils
- Problem
- Reduce resin-rich tow-gap defects, ply sinking, and out-of-plane fiber waviness in AFP laminates.
- Method
- Place PEI thermoplastic veils inside staggered tow-gaps and compare microscopy, micro-CT, tensile DIC, and progressive failure simulations.
- Result
- Lower surface waviness and improved x-direction strength and stiffness recovery.
Composite cure modeling
Bilamina Composite cure-induced deflection modeling
- Problem
- Predict cure-induced curvature and final deflection in a composite laminate.
- Method
- Model cure cycle temperature, degree of cure, glass-transition temperature, property evolution, thickness change, and curvature.
- Tools
- MATLAB, experimental temperature profiles, analytical laminate modeling.
- Result
- Predicted deflection compared with experimental measurements.
Kinetic theory
Integral-equation solution of the linearized BGK model for Couette flow
- Problem
- Describe rarefied Couette velocity fields from the linearized BGK model.
- Method
- Nondimensionalization, pure-shear simplification, and boundary conditions.
- Result
- Analytical reduction to an integral equation for velocity behavior.
Rarefied gas dynamics
Integral-equation analysis of Kramers flow using the linearized BGK model
- Problem
- Model rarefied gas motion over a flat plate with slip-flow behavior.
- Method
- Apply BGK linearization, boundary conditions, and asymptotic analysis.
- Result
- Integral-equation description of the Kramers velocity profile.
Numerical methods
RCIP for cornered integral equations
- Problem
- Solve singular Fredholm integral equations with corner singularities.
- Method
- Product Nystrom discretization and compressed inverse recursion.
- Result
- Stable high-accuracy integral-equation solution for BGKW Kramers flow.
Flow simulation
Coupled-pressure Navier-Stokes solver with multigrid Poisson acceleration
- Problem
- Accelerate incompressible lid-driven cavity flow simulation.
- Method
- Coupled pressure-velocity algorithm with multigrid Poisson solver.
- Result
- Reduced iteration counts and maintained benchmark accuracy.
LBM-MRT-MGM
Lattice Boltzmann MRT simulation of lid-driven cavity flow
- Problem
- Improve stability and efficiency for nearly incompressible cavity flow.
- Method
- Multiple-relaxation-time LBM with multigrid pressure correction.
- Result
- Fast, precise pressure-velocity solution for the cavity benchmark.
Publications
Journal papers and conference contributions.
Mitigating Out-of-Plane Fiber Waviness in AFP Laminates with Tow-Gaps via Selective Placement of Thermoplastic Veils
A. Ravangard, K. Celebi, S. G. Kravchenko, O. G. Kravchenko. Fibers, 13(11):145.
Effects of Biomass and Iron Catalyst on Yield of Plant-Based Graphitic Nanoplatelets
D. W. Mulqueen, A. Ravangard, J. D. Bhagatji, S. Kumar, O. G. Kravchenko. Materials Chemistry and Physics, 131629.
Compaction and Mechanical Performance of AFP Composites with Fiber Tow Gaps
A. Ravangard, O. Kravchenko. 24th International Conference on Composite Materials.
Reducing Out-of-Plane Fiber Waviness in AFP Laminate with Tow Gaps
A. Ravangard, O. Kravchenko. SAMPE Conference.
Mechanics of Resin Rich Regions Formation in AFP Preform with Staggered Fiber Tow Gaps
A. Ravangard, V. C. Jamora, J. D. Bhagatji, O. Kravchenko. Sixth International Symposium on Automated Composites Manufacturing.
Origin and Significance of Non-Uniform Morphology in AFP Composites
A. R. Ravangard, V. C. Jamora, J. D. Bhagatji, O. Kravchenko. American Society for Composites 38th Annual Technical Conference.
The Influence of Heat Transfer Due to Radiation from a Combustion Chamber
B. Razmjooei, A. R. Ravangard, L. Momayez, M. Ferchichi. Journal of Thermal Analysis and Calorimetry, 147(3):1901-1917.
Effects of Geometry on Simulation of Two-Phase Flow in Microchannel with Density and Viscosity Contrast
A. R. Ravangard, L. Momayez, M. Rashidi. Journal of Thermal Analysis and Calorimetry, 139(1):427-440.
A Numerical Investigation of Kenics Static Mixer as a Heat Exchanger in Separation and Segregation Process of Supercritical Carbon Dioxide
A. R. Ravangard, R. Kamali. Conference on Recent Advances in Aerospace and Associated Sciences.
Ph.D. in Mechanical Engineering at Old Dominion University, with prior M.Sc. work in Aerospace Engineering and B.Sc. training in Mechanical Engineering.
Composite manufacturing, experimental characterization, finite-element simulation, CFD, scientific programming, numerical methods, and machine learning.
Graduate teaching and research experience across Mechanical & Aerospace Engineering, Mathematics & Statistics, Engineering Management, and NSF-funded research.
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