1. PRESENTED BY: HOSSEIN GHAYOOR SUPERVISED BY: DR. SUONG V. HOA MODELING OF DEFORMATION OF DIFFERENT LAYERS DURING THE AFP PROCESS.

2. INTRODUCTION Viscoelastic properties Different properties of each layer Effect of time and temperature Understanding of residual stress and final state of material after manufacturing

3. INTRODUCTION Last Layer Layer 3 Layer 2 Layer 1 Mold Different Temperature Different Properties Viscoelastic Problem Figure From: Analysis of Process-Induced Residual Stresses in Tape Placement, F. Sonmez, H. T. Hahn, M. Akbulut, J. of Thermoplastic Composite Materials, 2002

4. VISCOELASTIC PROPERTIES OF CARBON-PEEK Creep Properties of PEEK Carbon fiber remains elastic Figure From: Characterization and modeling of nonlinear viscoelastic response of PEEK resin and PEEK composites, X.R. Xiao, C.C. Hiel, A.H. Cardon, Composite Engineering, 1994

5. VISCOELASTIC PROPERTIES OF CARBON-PEEK

6. The increase in number of unit cell columns (horizontal) The increase in number of unit cell rows (vertical) Five by five block of unit cell minimizes the effect of boundary conditions

7. VISCOELASTIC PROPERTIES OF CARBON- PEEK Creep/ Relaxation Properties of Carbon- PEEK composite

8. HOMOGENIZED PROPERTIES OF CARBON- PEEK Figure From: A thermoviscoelastic analysis of process-induced internal stresses in thermoplastic matrix composites, Sunderland P., Yu W., Manson J., Polymer Composites, 2001 C22

9. VISCOELASTIC FINITE ELEMENT Formulation:

10. NEW BOUNDARY CONDITIONS Attaching the nodes in the stiffness matrix

11. MULTI-LAYER Each 8-noded viscoelastic element can represent a unit cell (computational time is many times less) Different Scenarios can be analyzed Timing, thickness, temperature can be changed in the analysis

12. TYPICAL ANALYSIS RESULT One-step constant stress (one layer) two-step constant stress (one layer)

13. TYPICAL ANALYSIS RESULT One-step ramp stress (one layer) Time(s) Maximum Strain

14. TYPICAL ANALYSIS RESULT Depositing second layer Strain in the first layer (ramp stress) Time(s) Maximum Strain

15. TYPICAL ANALYSIS RESULT Strain in first layer (ramp stress) Second layer deposited third layer deposited fourth layer deposited fifth layer deposited Time(s) Maximum Strain

16. CONCLUSION Residual Strain/Stress can be predicted and can be used in manufacturing design to optimize the design. With developed modeling method different Scenarios of Manufacturing in terms of Timing, Thickness can be modeled and analyzed.

17. THANK YOU!