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Structures and Composite Materials Laboratory
CRIAQ COMP5CRIAQ COMP5Modelling Work ProgressModelling Work Progress
Erin QuinlanMcGill 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 limitationsUncontrolled flow
Fibre damageResin starvation
Eco
no
mic
lim
itat
ion
sT
her
mal
deg
rad
atio
n
Res
tric
ted
flo
wP
ract
ical
lim
itat
ion
s
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
materialscharacterization
science of processing
numerical implementation
data analysis & verification
‘raw’ material process compositepart
equations material properties
solve equations
what does it mean?
Structures and Composite Materials Laboratory
State VariablesDatabase
Void
AFP Machine
Thermo-chemical
FlowCompaction
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
umP Hdt
dcm
z
TK
zt
Tc
*
Heat generation due tocrystallization
Tool
z
Ply
Structures and Composite Materials Laboratory
Semicrystalline Thermoplastic• Heat generation
– c* : crystallinity of matrix
– mm : matrix mass fraction
– Hu : ultimate heat of crystallization of the polymer at 100% crystallinity
• Rate of degree of crystallinity– g : functional relationship– dT/dt : heating rate (cooling rate)
um Hdt
dcm
*
Tdt
dTg
dt
dc,
*
Structures and Composite Materials Laboratory
Flow-compaction Module
• The flow-compaction module is responsible for calculation of – prepreg consolidation– degree of intimate contact– autohesion
Phenomenon Mechanism
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 ModelRigid Flat Surface
Prepreg
ho
wo bo
t = 0
Rigid Flat Surface
Prepreg
hw b
t > 0
Papp
Degree of intimate contact Dic 00 bw
bDic
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
– w0 = b0
Dic : degree of intimate contact
Papp : consolidation pressure
0 : zero-shear rate viscosity
5
12
0
0
000
1012
1
1
t
w
hP
bw
hhD appoic
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 Contactt=0
PartiallyDiffused
t>0
CompletelyDiffused
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
TCT
a
T
Ta
tTCG
tGR
T
T
IC
IC
5
21
1094.1
46926.11
469604.1log
)(
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 heatApply 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” http://www.automateddynamics.com/
• “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. 1040-1062.
• 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. 421-440.
