1. Uniting composite manufacturing theory and application
Practical manufacturing methods in a team-based curriculum
Michael Knauf, Eduardo Barocio, Justin Miller, Matthew Prall, Orzuri Rique Garaizar, Drew Sommer, Orion Wingfield, Dr. Nathan Sharp, Dr. Ronald Sterkenburg
Professor: Dr. R. Byron Pipes

2. introduction Composites education
Universities and ABET share common goals: Prepare graduates for successful careers
ABET criteria specify many outcomes, including preparing graduates to be able to:
Design and conduct experiments
Design systems and processes to meet desired needs
Identify, formulate, and solve engineering problems
Purdue’s Manufacturing of Advanced Composite Materials course links an understanding of the mechanics of composites to the design and manufacturing of composite systems
This course trains students in thermoset reaction kinetics, rheology, heat transfer, fiber bed permeability and compaction, void formation, Darcy flow, and thermal and chemical shrinkage
These concepts are combined to study the effects of cure cycles on the cure state of composites, residual deformations and stresses, and optimal processing conditions, culminating in a final project

3. Course material Composites education
Lab 1: Lab tour at Applied Composites Engineering
- Manufacturing, Tooling, QC, Engineering, and Maintenance, Repair, & Overhaul
Lab 2: Polymer cure kinetics and viscosity
- Differential Scanning Calorimetry of HexPly 8552 calibrated autocatalytic, diffusion controlled phenomenological model to determine degrees of cure
- Rheometry used to determine viscosity as a function of degree of cure using Castro-Macosko model (prior to gel point)
Lab 3: Convective and conductive heat transfer
- One dimensional heat transfer model calibrated to simulate temperatures
(and thus degree of cure) within a composite part curing in an autoclave
Lab 4: Autoclave heat transfer
- Two dimensional heat transfer models produced to simulate effects of autoclave
parameters on polymer degree of cure and viscosity

4. Course material Composites education
Lab 5: Consolidation and debulking
- Dry fiber consolidation measurement and modeling
- Void content measurement of varying levels of applied consolidation pressure
Lab 6: Darcy flow
- Permeabilities of fiberglass plain weave measured in warp, weft and 45° directions
Lab 7: Thermal and cure shrinkage
- Decoupled chemical and thermal shrinkage to determine residual deformations and stresses due to these two phenomena
Lab 8: Cure cycle optimization and modeling
- Combined models used to predict degrees of cure, viscosity, and resin layer thickness to optimize autoclave cure cycles for Hexcel IM system

5. Manufacturing project
Composites education
Culminating manufacturing project required the knowledge gained from the previous laboratory experiments
Four groups of three students each:
Autoclave process with prepreg plain weave (Hexcel 196-P/8552)
Out of autoclave process with prepreg plain weave (Hexcel 196-P/8552)
VARTM process with dry plain weave (BMS9-8 fabric/ 4281A/4286B Epoxy)
Discontinuous unidirectional prepreg compression molding (IM7/8552)
MH 116 airfoil
Incorporates varying geometry and twist angles
Reasonably producible by all four methods
All other processing requirements determined by individual teams

6. Manufacturing project
Ply layup schedules
Autoclave team utilized Catia for ply layup schedule
VARTM team utilized MATLAB for ply layup schedule
Both methods produced very similar ply shapes

7. Manufacturing project
Tool designs
Autoclave, Out of Autoclave, and
VARTM tool
Compression molding tool

8. Manufacturing project
modeling
Autoclave team utilized Raven for optimized (highest degree of cure) autoclave cycle
Out of Autoclave team utilized MATLAB coupled heat transfer & cure kinetics analyses for optimized oven cycle
Compression molding team performed similar cure cycle analyses and utilized ANSYS for thermal residual stress analysis

9. Manufacturing project
modeling
VARTM team modeled flow characteristics for resin transfer and utilized Gutowski model for Vf predictions

10. Manufacturing project
Manufacturing – Autoclave & out of autoclave
Autoclave & Out of Autoclave teams used similar procedures for layup and cure
Experiment followed trends, errors from:
Thermocouple placement
Complex 3D shape vs 1D simulation

11. Manufacturing project
Manufacturing - Autoclave
1D Darcy Flow Prediction: 3.6 min
VARTM & compression molding methods considerably different
VARTM flow prediction errors due to 1D analysis vs complex 3D shape
Compression molding included filling cavity with charge and applying heat/pressure to tool
Some areas fully wetted: 4.5 min
Actual 3D flow time: ~6 min

12. Manufacturing project
results
All parts showed good dimensional tolerances and consolidation followed logical trends

13. conclusions Composites education
Experiments provided solid basis for students’ understanding of phenomena involved in manufacturing advanced composites
Manufacturing project demonstrated strengths and weaknesses of four mutually exclusive manufacturing techniques
Excellent course fulfilled university and governing board desires for preparing graduates in composite manufacturing