Multiphase, Dual Polymer Injection Molding & Cooling of Open Cavity

Transcription

1 . Presented at the COMSOL Conference 2009 Boston and Milan Research & Development, FEA, CFD, Material Selection, Testing & Assessment Multiphase, Dual Polymer Injection Molding & Cooling of Open Cavity to form both distinct & graduated material properties within a complex body Presenter: Mark Yeoman Date: 16 October 2009

2 Implant Design General Soft Tissue Mechanics Nonlinear, Hyper-elasticelastic Anisotropic/Orthotropic Viscoelastic Ligament Replacement & Augmentation System (LARS), used for massive rotator cuff repair Ideal Implant Mechanics cs Duplicate or augment the natural response of body tissue/ physiological function

3 Novel LARS Implant Novel elastomeric, rotator cuff LARS

4 Material Regions Polymer 1 Graduated Region Generalized Force Displacement Material Region Curves A A Polymer 2 Force Section A-AA B B Section B-B Displacement

5 Manufacture Process Aim is to find the production & process parameters required to produce the elastomeric implant, using a single injection mold process. Reduce production o costs Single process Reduce physical handing Increased production yields Reduce QC steps Increase integrity & homogeneity of implant Reduces the delaminating & bonding issues found in layered production process

6 Model Geometry Model Geometry, Domains & Boundary Conditions Initial Subdomain Phases Gas (Atmosphere) Solid (Mold) Fluid (Polymer Solution)

7 COMSOL Model Overview 3 Transient Modules utilized: Two-Phase Flow Laminar Phase Field (chns) Phase Field (mmpf) Convection & Conduction (cc) Two-Phase Flow Laminar Phase Field Models Fluid-Air Boundary Flow Phase Field Models 2 dual injected polymer solutions Convection & Conduction Models thermal changes (Solid, Fluid & Gas)

8 Density & Viscosity Functions Change in dynamic viscosity it & density vs. temperature t for the two polymer solutions used in the injection mold process

9 Inlet Injection Process Mold machine polymer 1 & polymer 2 injection flow profiles vs. time.

10 Simplified Inlet Condition Simplified inlet condition to equivalent condition: Smooth inlet flow function implemented Combined flow rate & volume fraction

11 Equations & Boundary Conditions (T cc ) fluid chns = (T cc ) poly 1 +{[ (T cc ) poly 2 - (T cc ) poly 1 ] Vf poly mmpf 2 } cc = chns (T cc ) = (T ) +{[ (T ) - (T ) ] Vf fluidf poly p y 1 poly p y 2 poly p y 1 poly p y 2 chns cc cc cc mmpf } k C u cc =A phi p cc chns =D phi +B chns cc = ummpf=uchns +E Subscripts = Superscripts = Poly 1 = Poly 2 = A, B, D & E = k = C p = u = COMSOL Multiphysics module Material phase or state: solid, gas, fluid 1st Polymer material/solution 2nd Polymer material/solution Various material dependent constants Thermal Conductivity Heat Capacity Velocity Field

12 NB: Validation data done on a different 3D Body Validation (Thermal Data) Time dependentd thermal response curves of validation ld model vs. physical data at three different & distinct locations

13 NB: Validation data done on a different 3D Body Validation (Cured Sections Data) Partial view of acuredsectionof a molded device, illustrating the distinct cured polymeric regions (1 & 2) and comparison to the equivalent COMSOL model.

14 Fluid Fill & Polymer Regions

15 Thermal Effects During Filling

16 Continued Flow After Injection

17 Conclusions COMSOL Model successfully modeled the filling & curing of an open cavity mold with a combined polymer solution at an elevated temperature through a single port to produce vary graduated and distinct materials regions The COMSOL Model developed was validated against: Quantitative thermal data Quantitative cured sections Qualitatively against captured video footage of filling process NB: Validation data done on a different 3D Body

18 Future Developments Additional polymer solution (3rd polymer) Multiple inlet & outlet locations across the mold cavity Time dependent curing function (specifically required for 3rd polymer) Multi-parameter optimization of the injection flow inlet profiles, mold temperature & polymer inlet temperatures

19 . Research & Development, FEA, CFD, Material Selection, Testing & Assessment Contact Details Dr Mark Yeoman E: M: +44 (0) T: +44 (0) W: