Structures and Composite Materials Laboratory CRIAQ COMP5 Modelling Work Progress Erin Quinlan McGill University February 16, 2009

Structures and Composite Materials Laboratory Outline Background Objectives Modelling approach Work plan Next steps

Structures and Composite Materials Laboratory Thermoplastic Composites Processing Comprehensive Composite Materials

Structures and Composite Materials Laboratory Consolidation Steps Plies come into contact with each other with added temperature and pressure Resin flow begins to fill the voids Polymer chains link together (autohesion) Fibres impregnate through the resin Cooling and crystallization

Structures and Composite Materials Laboratory Processing Window Cooling rate, log (dT/dt) Pressure High void content Equipment limitations Uncontrolled flow Fibre damage Resin starvation Economic limitations Thermal degradation Restricted flow Practical limitations Optimal processing region Comprehensive Composite Materials

Structures and Composite Materials Laboratory Objectives Model the thermoplastic tape behaviour during the Automated Fibre Placement (AFP) process Tool New ply Laminate Pressure Temperature

Structures and Composite Materials Laboratory Modelling Approach materials characterization science of processing numerical implementation data analysis & verification raw material process composite part equations material properties solve equations what does it mean?

Structures and Composite Materials Laboratory State Variables Database Void AFP Machine Thermo- chemical Flow Compaction Input Output Typical Process Model Architecture

Structures and Composite Materials Laboratory Thermochemical Module The thermochemical module is responsible for calculation of –temperature in the structure of interest –degree of crystallinity in composite components The thermochemical module consists of a combination of analyses for heat transfer and crystallization kinetics.

Structures and Composite Materials Laboratory Laminate Semicrystalline Thermoplastic Thermal Analysis Heat generation due to crystallization Tool z Ply

Structures and Composite Materials Laboratory Semicrystalline Thermoplastic Heat generation –c*: crystallinity of matrix –m m : matrix mass fraction –H u : ultimate heat of crystallization of the polymer at 100% crystallinity Rate of degree of crystallinity –g: functional relationship –dT/dt: heating rate (cooling rate)

Structures and Composite Materials Laboratory Flow-compaction Module The flow-compaction module is responsible for calculation of –prepreg consolidation –degree of intimate contact –autohesion PhenomenonMechanism Interfacial bond formation (consolidation) Autohesion Interfacial deformation (coalescence) Viscoelastic deformation of prepreg tows

Structures and Composite Materials Laboratory Modelling Consolidation Intimate contact Interply bonding

Structures and Composite Materials Laboratory Prepreg Interply Intimate Contact Modelling approach: –Characterize prepreg surface roughness –Measure neat resin viscosity –Fluid mechanics Modelling results: –Time required to achieve complete interply intimate contact for a given set of temperature, pressure and prepreg geometric parameters Verification –Optical microscope –Scanning acoustic microscope

Structures and Composite Materials Laboratory Prepreg Surface Roughness Model

Structures and Composite Materials Laboratory Single Ply Model Rigid Flat Surface Prepreg hoho wowo bobo t = 0 Rigid Flat Surface Prepreg h wb t > 0 P app Degree of intimate contact D ic

Structures and Composite Materials Laboratory Single Ply Model Assumptions: –Squeezing flow between two rigid parallel plates –Viscous laminar flow –Viscosity is independent of shear rate –w 0 = b 0 D ic : degree of intimate contact P app : consolidation pressure 0 : zero-shear rate viscosity

Structures and Composite Materials Laboratory Neat Resin Rheology

Structures and Composite Materials Laboratory Degree of Intimate Contact Versus Time APC-2 Prepreg surface against a rigid flat surface

Structures and Composite Materials Laboratory Autohesion Phenomenon Initial Contact t=0 Partially Diffused t>0 Completely Diffused t=t Interface Chain Like Molecules

Structures and Composite Materials Laboratory Autohesive Strength Measurements

Structures and Composite Materials Laboratory Autohesive Strength Measurements

Structures and Composite Materials Laboratory Isothermal Autohesion Model T is in °K

Structures and Composite Materials Laboratory Modelling Void Fraction Voids form after heating during the consolidation phase Resin Void Fiber

Structures and Composite Materials Laboratory Void Formation Apply heat Apply pressure

Structures and Composite Materials Laboratory Void Fraction Content vs. Pressure

Structures and Composite Materials Laboratory Work Plan Model development: –Implement 1D heat transfer model –Implement crystallinity kinetics model –Tape machine heat source model Material characterization –Crystallinity model –Tape roughness measurement Validation experiments –Get temperature-time data from AFP experiments (effect of pressure, temperature, layup speed)

Structures and Composite Materials Laboratory References Automated Dynamics Thermoplastic Composites: Module 6 S. Ranganathan, S.G. Advani, and M.A. Lamontia, A Non- Isothermal Process Model for Consolidation and Void Reduction During In-Situ Tow Placement of Thermoplastic Composites, Journal of Composite Materials 29(8), 1995, pp J.M. Tang, W.I. Lee, G.S. Springer. Effects of Cure Pressure on Resin Flow, Voids, and Mechanical Properties. Journal of Composites 21, 1987, pp