Aircraft Aging and Durability Project Aircraft Aging and Durability Project Progressive Damage Analysis Progressive Damage Analysis of Composites of Composites Carlos G. Carlos G. Dávila Dávila Cheryl A. Rose Cheryl A. Rose External Collaborators External Collaborators Pedro P. Pedro P. Camanho Camanho Pere Maimí Pere Maimí , Albert , Albert Turon Turon
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Aircraft Aging and Durability ProjectAircraft Aging and Durability Project
• New cohesive law uses Paris Law to account for fatigue
damage growth (Turon-Camanho, 2007).
• Propagation law bounded by threshold and overload fracture.
• Model accounts for mode mixity GI/GII and load ratio, R.
• Model uses “standard” material properties.
• “Cycle Jump” strategy used to reduce re-calculations of
structural response.
m
cG
GC
N
A
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!
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N
A
Simulation of Fatigue Simulation of Fatigue Delamination Delamination GrowthGrowth
Double Cantilever Beam
0,2 0,3 0,4 0,5 0,6 0,7 0,80,911E-6
1E-5
1E-4
1E-3
0,01
dA
/dN
GImax
/GIc
Numerical Experimental
Asp, Sjogren, Greenhalgh, J.
Comp. Tech. Res., 2001.
Mixed Mode Propagation
Simulation of Fatigue Simulation of Fatigue Delamination Delamination GrowthGrowth
Fatigue growth of facesheet debond
Material
Characterization
Model of sandwich with fatigue cohesive elements Predicted
Life
Pressure
Traction-Displacement Laws for R-curve EffectsTraction-Displacement Laws for R-curve Effects
Experiments show that toughnessGc is a function of crack length, a.
A trilinear traction law for cohesive elements and forcontinuum damage models can account for thetoughening effect of fiber bridging and fiber pullout.
F
TestOriginal
Gc=75
Original, Gc=150
Lo
ad
, N
Applied displacement, mm.
Modified
Trilinear
F
Test results: Pinho, ’06, Imperial College, UK.
Damage Toleranceanalysis of fuselage
Original and modifiedsoftening law for R-Curve
F
Symmetric FE model of CT specimen
High Fidelity Analyses: High Fidelity Analyses: Micromechanical levelMicromechanical level
0º
90º
Matrix crack
Delamination
90º
0º
0º
Transversely Isotropic Damage Model
High Fidelity Analyses: TIDMHigh Fidelity Analyses: TIDM
Transversely Isotropic Damage ModelTransversely Isotropic Damage Model
Damage Models: Summary of ProgressDamage Models: Summary of Progress
Continuum damage model:Continuum damage model:! Uses LaRC04 criteria to account for all failure mechanisms.
! Energetic regularization using element size avoids mesh-dependency.
" Improved kinematic representation of ply damage needed when damage mode
interaction is important.
Cohesive models:Cohesive models:! Rigorous kinematic representation of a strong discontinuity.
! Possesses built-in energetic regularization.
! Newly developed shell and fatigue cohesive models.
" Previous information of the possible fracture planes is required.
Traction Curves for R-Curve Effect:Traction Curves for R-Curve Effect:! R-Curve toughening can be modeled with trilinear traction-displacement laws.
High-Fidelity 3D Models:High-Fidelity 3D Models:! Transversely Isotropic Damage Model can capture all modes of matrix cracking:
• crack initiation and propagation through the thickness and along the fibers.• process of crack saturation.• linking of matrix transverse cracks and delamination.
" Requires several elements through the thickness of every ply.