Thin ply composites: Experimental characterization and modeling
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Thin ply composites: Experimental characterization and modeling ICCM19 Montréal 2013 In partnership with North-TPT, FHNW, RUAG Technology, RUAG space, and Connova Robin Amacher, Joël Cugnoni , John Botsis Ecole polytechnique fédérale de Lausanne , Switzerland
description
Thin ply composites: Experimental characterization and modeling. In partnership with North-TPT, FHNW, RUAG Technology, RUAG space, and Connova. ICCM19 Montréal 2013. Robin Amacher , Joël Cugnoni , John Botsis Ecole polytechnique fédérale de Lausanne , Switzerland. - PowerPoint PPT Presentation
Transcript of Thin ply composites: Experimental characterization and modeling
Thin ply composites: Experimental characterization and modeling
ICCM19 Montréal 2013
In partnership with North-TPT, FHNW, RUAG Technology, RUAG space, and Connova
Robin Amacher, Joël Cugnoni, John Botsis
Ecole polytechnique fédérale de Lausanne , Switzerland
o Advantages: Improved delamination resistance, higher onset of damage & ultimate failure Improved fatigue properties and in some case damage tolerance More design degrees of freedom = more optimal laminate Easier to design ply drops / small angle laminates / local reinforcements Can produce “homogeneous” laminates, no more dependency on stacking Can produce mixed “thin & thick” laminates for structures with large shell thickness variations. Thin ply materials are now commercially available
o Challenges:o Characterization and understanding of ply-thickness effect for a wide range of constituentso Efficient and accurate models for prediction of thin ply composite performanceo Flexible manufacturing (assembly of complex preform) & automation to reduce layup timeo Develop & validate efficient design method to account for the performance benefit without
blowing up the degree of complexity of the problem
Relevant literature (small subset): [1] S. Sihn, R.Y. Kim, K. Kawabe, S. Tsai, Experimental studies of thin-ply laminated composites, Composites Science and Technology, 67, 2007[2] M.R. Wisnom, B. Kahn, S.R. Hallet, Size effects in unnotched tensile strength of unidirectional and quasi-isotropic carbon/epoxy composites,
Composite Structures, 84, 2008[3] A. Arteiro, G. Catalanotti, J. Xavier, P.P. Camanho, Notched response of non-crimp fabric thin-ply laminates, Composites Science and
Technology, 79, 2013
Why Thin Ply composites?
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
Thin ply : below 125 g/m2, down to 15g/m2 today
Objectives: Understand, characterize and model thin ply composites from the ply level to part level.
Experimental study of thin ply size effects • Constant specimen thickness • UD prepregs of varying ply thickness & number of
sub-laminate repetitions Material• North TPT Thin ply composites UD prepreg with
ATL production of complex laminates• Thick = 300 (2x150) g/m2 ~300 microns / ply• Intermediate = 100 g/m2 ~100 microns / ply• Thin = 30 g/m2 ~30 microns / ply• M40JB fiber / NTPT TP80ep (80°C epoxy resin)
from the same batches and production on the same machine the same week. Autoclave production, 55% fiber volume fraction
Objectives & Method
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
Experimental characterization of Thin-ply size effects
UD ply level properties
o Thin Ply : more uniform microstructure and improved 0° compressive strength
Compressive strength (ASTM D5467*)
Thick 300 g/m2
Intermediate 100g/m2
Thin 30g/m2
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
o Overall no change in intrinsic lamina properties when reducing ply thickness
o One exception: 0° compression
Quasi isotropic laminate, tensileASTM D3039, constant thickness, sub-laminate scaling: [+45°/90°/-45°/0°]ns with n=1 for thick, n=3 for interm. and n=10 for thin ply.
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
Damage (Acoustic emission)
Appl
ied
stre
ss
QISO tensile properties
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
Ultimate strength: +42%
[+45°/90°/-45°/0°]ns
n=1
n=3n=10& n=3
Onset of damage: +227%
Change of failure mode:• Thick: extensive
matrix cracking & delamination
• Thin: brittle rupture by fiber failure (max strain of fiber)
• Little effect of n
Open Hole Compression
Intro
Lamina level
Checklist
Simulation
Design
Laminate level
Element level
+18%
Open Hole Compression [+45°/90°/-45°/0°]ns (ISO 14126 / ASTM D6484)
OHC
Str
engt
h [M
pa]
Open Hole Tensile fatigue
o Lower static ultimate strength. No damage around hole means no stress concentration relief but better predictability (Wisnom & al)
-34%
+31%Thick plies 300g/m2, n=1 @12k cycles, 316MPa
Thin plies 30g/m2, n=10 @1M, 316MPa
[+45°/90°/-45°/0°]ns
Ruin = -10% stiffness
o Strong improvement in fatigue life (<20k vs >1M cycles)
Open Hole Tensile: static and fatigue (ASTM D5766 & D7615, R=0.1)
Intro
Lamina level
Simulation
Design
Conclusion
Laminate level
Element level
Bolted joint bearing strength
o Strength improvement for as produced @ 20°C +18%o Strength improvement for Hot Wet @ 90°C +58%
Single lap bearing test, standard and Hot Wet condition (ASTM 5961), fastener type EN-6115Hot Wet cond. 95%RH/70°C, test 90°C
sbr_ult = 156 MPa
sbr_ult = 476 MPasbr_ult = 573 MPa
sbr_ult = 294 MPa
sbr_ult = 584 MPa
sbr_ult = 372 MPa
Thick Ply 300g/m2, n=2 Intermediate 100g/m2, n=5 Thin Ply 30g/m2, n=18
Hot Wet 90°C
Hot Wet 90°C
As Produced, 20°C
As produced, 20°C
Intro
Lamina level
Simulation
Design
Conclusion
Laminate level
Element level
[+45°/90°/-45°/0°]ns
Low energy impact
o Transition of failure mode from delamination to fiber failure
o An optimal ply thickness can be found to achieve the smallest damage area
o Thin-Ply technology allows tailoring the material properties wrt impact induced damage
Intro
Lamina level
Summary
Simulation
Design
o Rectangular specimen clamped on the short sides; bending is dominant QI [0°/+45°/90°/-45°]ns, 300 x 140 x 2.4 mm Thick (300 g/m2) n=1, Intermediate (100g/m2) n=3, Thin (30g/m2) n=10
o Energy: 11.5 J & 18J
Back
side
THICK, n=1 INTERMEDIATE, n=3 THIN, n=10
delamination delamination &fiber failure
mostlyfiber failure
Laminate level
Element level
Modeling of Thin-ply size effects
Ply thickness effects:1. reduction of interlaminar shear
stresses at the free edges & delayed free edge delamination
2. Constrained intra laminar transverse cracks => apparent 90° and in-plane shear strength increase => in-situ ply strength model (*)
3. Matrix cracking induced delamination also delayed by constraining plies
4. Other mechanisms (bridging?, plasticity of matrix?)
Modeling thin-ply size effects
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
2D generalized plane strain or 3D continuum model
In-situ shear / normal strength (*) + coarse 3D modelOr high fidelity 3D continuum model + cohesive zone
High fidelity 3D continuum model + cohesive zone
(*) Camanho et al., Composites Part A, 37, 2006 Fracture mechanics : onset ~ 1/sqrt(t)
Simulation of ‘thin ply’ effectso Goal: capture the transition in dominant failure mode in order to
understand and predict ply size effects with interacting damage modeso Hypotheses:
no change in intrinsic properties of ply and interface wrt ply thickness
First ply: 0° (symetry)
User material withfiber failure (subroutine)
UD mx. without fiber failure
Cohesive elements> lateral cracking
2nd ply: -45°3rd ply: 90°
Between the layers: cohesive surfaces => delamination
Simulation: force controlled(sigmoid ramp, quasi-static)
o High fidelity 3D modeling of quasi isotropic unnotched tensile test in Abaqus Explicit, [45°/90°/-45°/0°]ns laminate.
o All material properties coming from tests, no fitting parameters.
Intro
Lamina level
Conclusion
Design
Simulation
Laminate level
Element level
Cohesive elements=> Intralaminar matrix cracking
45°90°
-45°0°
User material withfiber failure (subroutine)
Symmetry BC
Simulation of ‘thin ply’ effectso Damage models: cohesive interfaces between plies,
cohesive elements for transverse cracking, continuum damage model for fiber failure
o Mesh convergence study: 6 linear hex. element C3D8R per ply thickness, 0.5mm in plane elem. size, up to 650k elements, 2.1M dofs
o Mass scaling & time step convergence study: dt = ~5e-6 s, ~500’000 time steps
Intro
Lamina level
Conclusion
Design
Simulation
Laminate level
Element level
0
100
200
300
400
500
600
700
800
0 2 4 6 8
Stre
ngth
[MPa
]
# elements ply thickness
#element/ply & mass scaling target dt
1e-4_ultimate strength
1e-4_onset of damage
5e-5_ultimate strength
5e-5_onset of damage
1e-5_ultimate strength
1e-5_onset of damage
5e-6_ultimate strength
5e-6_onset of damage
Thick ply (300 g/m2) QISO tensile
Intro
Lamina level
Conclusion
Design
Simulation
Laminate level
Element level
Delamination damage Intra laminar cracking(matrix failure) Fiber failure
Thick ply (300 g/m2) QISO tensile
Damage sequence: o cracking of 90° ply, then cracking of 45° plies & delamination from edgeso Final failure after extensive delamination / damage of all off-axis plieso Ultimate strength: fiber failure in 0° plies with all other plies broken
Intro
Lamina level
Conclusion
Design
Simulation
Laminate level
Element level
Intermediate ply (100 g/m2), n=3
Damage sequence: o cracking of 90° plies then outer 45° ply then final failure (localization of damage
starting from the free edges and fiber failure in 0° plies o Transverse normal and shear cracking delayed, Delamination nearly suppressed
Intro
Lamina level
Conclusion
Design
Simulation
Laminate level
Element level
Simulation of ‘thin ply’ effects
o Good predictions for thick & intermediate ply thickness for both onset of damage and ultimate strength.
o High fidelity FE model can capture the change of damage mode sequence wrt ply thickness (with constant intrinsic properties)
o Coarse 3D FE Models (1 elem/ply) with in-situ strength (scaled by 1/sqrt(t)) provide comparable results, could be extended towards shell modeling (work in progress)
FE Analysis
Intermediate100 g/m2
Thick300 g/m2
Towards part level modeling and design
Intro
Lamina level
Design
Model First ply failure 0° ply failure Experiment Damage Ult strengthCLT with damage 287 MPa 609 MPa Thick ply 300g/m2 248 MPa 595 MPa
Simulation
Conclusion
Laminate level
Element level
High fidelity 3D FE modeling
Shell models or CLT with in-situ
strength
Com
puta
tion
time
All damage modes with interactions
o Thin Ply composites : closer to classical laminate theory as no delamination!!Model First ply failure 0° ply failure Experiment Damage Ult strength
CLT with damage 287 MPa 609 MPa Thick ply 300g/m2 248 MPa 595 MPa CLT no damage 287 MPa 819 MPa Thin ply 30g/m2 821 Mpa 847 MPa
Separate damage models for transverse cracking and
delamination
Coarse 3D FE modeling with in-
situ strength
Damage models for transverse cracking
Delamination
Delamination follows intra laminar cracking(no complex interaction)
Ply thickness small enough to avoid delamination
o Advantages: Improved delamination resistance, higher onset of damage & ultimate failure Improved fatigue properties and in some case damage tolerance More design degrees of freedom = more optimal laminate Easier to design ply drops / small angle laminates / local reinforcements Can produce “homogeneous” laminates, no more dependency on stacking Can produce mixed “thin & thick” laminates for structures with large shell thickness variations. Thin ply materials are now commercially available
o Challenges:o Characterization and understanding of ply-thickness effect for a wide range of constituentso Efficient and accurate models for prediction of thin ply composite performanceo Flexible manufacturing (assembly of complex preform) & automation to reduce layup timeo Develop & validate efficient design method to account for the performance benefit without
blowing up the degree of complexity of the problem
Why Thin Ply composites?
Intro
Lamina level
Laminate level
Element level
Simulation
Design
Conclusion
Thin ply : below 125 g/m2, down to 15g/m2 today
