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Thomas L Attard, Ph.D. Associate Professor
Department of Civil, Construction, and Environmental Engineering
Chairman, Structural Engineering & Mechanics for the Athens Institute for
Education and Research (ATINER)
The University of Alabama at Birmingham
The 6th Kwang-Hua Forum on Innovations and Implementations in Earthquake
Engineering
December 12 – 14, 2014
Shanghai, China
NEXT GENERATION HYBRIDIZED
POLYMERIC “TUNED” COMPOSITES FOR
21ST CENTURY ADVANCES IN EARTHQUAKE
ENGINEERING
PROBLEM STATEMENT AND GENERAL RESEARCH OBJECTIVE &
OUTCOME
Today‟s society is complex, variable, and high-demanding, subject to
multi-natural hazards and extreme anthropogenic loads
Objective: Develop a Pervasive damage mitigation system for
complex structures
Carbon-Fiber-Reinforced Hybrid-Matrix Composite (CHMC)
Strategy: Develop a multi-scale design solution from the molecular
level to the macro/ component/ large-scale level for various
structural components
Outcome: A systems composite that provides superior physical,
chemical, and mechanical properties to new (strengthening) or
already-damaged (retrofit) structures
NEWLY FUNDED CHMC RESEARCH PROGRAM
New 3-year funded research project for $746,709 (3 PhD
Students are sought)
Sponsor is US Army Corps of Engineers and Presidium Group of Companies
Drawbacks of many conventional fiber-reinforced epoxy systems
Lack sufficient energy dissipation and ductility
Lack fracture toughness capability
High-rate of debonding from the substrate
Suspect chemical and environmental durability
Dual polymeric hybridization alleviates many of
the above shortcomings
CHMC: Combine strong carbon-based technology with hybridized
chemical reactions
Lightweight
Design a materials system with „tune-able‟ properties. Provide:
Impact-resistance
Energy dissipation and ductility
Fracture toughness
Damping for the vibration control of elastic systems
Prevent Laminate- Substrate Debonding via an internal energy
dissipation mechanism
Excellent chemical and environmental durability
CHMC APPLICATIONS TO EARTHQUAKE-DESIGNED
INFRASTRUCTURES
DAMAGE MECHANISMS OF GENERAL LAMINATE FIBER-REINFORCED COMPOSITES
Damage Mechanisms of General
Laminate Fiber-Reinforced
Composites
Matrix cracking
Fiber–matrix debonding
Fiber breakage
Fracture of fiber
Fiber pullout
Follows fiber fracture
Separation of fiber from matrix
Develop a design standard
from the „ground-up‟
that can be utilized as a
pragmatic engineering
solution
①
②③
④
①
②
③
④
Given a non-homogeneous microstructure
Existence of numerous paths for load redistribution
The composite integrity of the CHMC depends on the accumulated sub-
critical damage rather than any single damage event
Thus, macroscopically strong solids protect integrated microscopically weak
structures
EVOLUTIONARY NATURE OF THE FAILURE CHARACTERISTICS OF VARIOUS COMPOSITES
RESULT: local damage (single crack) does not result in
catastrophic global failure of the composite
OUTCOME OF THE HYBRIDIZED CHMC
.
“ONE-STOP SHOP/ ONE-STOP SOLUTION”
An alternative mode of material failure is created
Deformable body is thus TRAPPED in a microscopically weak, but
macroscopically strong, mode of fracture … Crack propagation is precluded
Micromechanical
Behavior of the
Constituent Materials
Interaction between
Constituent Phases
Micromechanics &
Micro-scale Damage
model
Results &
Inference
Macro-scale Mechanical
Behavior of Materials
Scale-linking
Model
Large-scale Structural
Applications
Stress-strain
Behavior
Energy
Dissipation
Impact
Resistance
Engineering
Mechanics
MULTI-SCALE MODELING: ACROSS ALL SCALES
TEM
Molecular
Dynamics
Micro-structure (SEM)
Manufacturing
Process
Material Interfaces
(e.g., Fiber-Matrix)
Micro-mechanics
Stress-Strain
Vibration/
Damping
Engineering
Applications (hybrid testing)
Multi-scale modeling (across all scales) … Dimensional Scales
Fiber Push-out
Chemical
Analysis
Defects & Damage
10-9 m 10-6 m 10-1 m 10 m
Fatigue
Tolerance
Spiral Notch Torsion Test
Micro-Tens Test (polymers)
Impact resist.
HIGH-IMPACT RESISTANCE OF THE CHMC
High-Impact Tests at the ORNL (DoE)
0 10 20 30 40 50
-5
0
5
10
15
20
Fo
rce
(kN
)
Displacement (mm)
CarbonFlex
Carbon-fiber/ epoxy
Load time-histories
Carbon-fiber epoxy CHMC
(1) (2) (3) (4)
Formation of
local buckles
Progressive folding
MATERIAL DAMPING AND IMPACT RESISTANCE OF STEEL BEAMS: HIGH-FREQUENCY VIBRATION
DAMPING RATIOS:
CHMC beam 4.87%
CFRP beam 1.18%
Steel beam 0.35%
Steel CF/
Epoxy
CHMC1 CHMC2 CHMC30
2
4
6
Da
mp
ing
Ra
tio
Tes
ted
by
Fre
e V
ibra
tio
n (
%)
0.35%
1.18%
4.87%
4.29% 4.17%
0 100 200 300 400 50010-11
10-10
10-9
10-8
10-7
10-6
10-5Power Spectral Density (0.3g)
Frequency (Hz)
Pow
er-d
isp
. /H
z2
CFRP
CHMC (CarbonFlex)
Velocity Time-history
Damping Ratio vs
Thickness (CHMC)
0.00
1.00
2.00
3.00
4.00
5.00
CFRP 1/16 1/8
Dam
pin
g R
ati
o (
%)
Thickness hp (in)
Damping Ratio vs tc (CHMC)
4.00
4.20
4.40
4.60
4.80
2 3 4 5Intermittent Curing Time tc (hr)
Dam
pin
g R
ati
o (
%)
damping varying with
hp
Damping varying
with tc
0.0 0.4 0.8 1.2 1.6 2.0
-0.08
-0.04
0.00
0.04
0.08
Time (sec)
0.0 0.4 0.8 1.2 1.6 2.0
-0.08
-0.04
0.00
0.04
0.08
Vel
oci
ty (
mm
/s)
Time
(Sec)
0.0 0.4 0.8 1.2 1.6 2.0
-0.20
-0.10
0.00
0.10
0.20
Steel
Time (Sec)
Carbon-fiber/ Epoxy
CHMC (CarbonFlex)
CHMC RETROFIT OF A SEISMICALLY DAMAGED RC SHEAR WALL
n Cyclic testing of an RC shear wall specimen
n Resulting in a 3mm-wide cross-crack and crushed concrete at the two bottom
corners of the specimen
n After-test load capacity: approximately 40% of its peak value
TEST SETUP AND RESULTS -- RC SHEAR WALL
LVDT
LVDT
LVDT
Actuator to Apply Lateral Load
Hydraulic Jack to Apply Vertical Load
Bolt to Anchor the Specimen
Test Setup Lateral Force-Disp. Response
Results: CHMC retrofit of the shear wall recovered 80% of the
original load capacity, in addition to significantly increasing ductility
and confinement
-30 -20 -10 0 10 20 30
-300
-200
-100
0
100
200
300
As-it RC Shear Wall (Hysteresis)
CarbonFlex Retrfitted (Hysteresis)
As-it RC Shear Wall (Backbone)
CarbonFlex Retrfitted (Backbone)
La
tera
l F
orc
e (
KN
)
Lateral Def. (mm)
PPP
PPP
TEST SETUP AND RESULTS -- RC SHEAR WALL
Note the tremendous ductility in the
shear wall. Tremendous energy
dissipation helped stabilize the crack
growth in the wall and sustain its high
strength even after the concrete crushed.
Note also the tremendous confinement
and compression strength in the wall.
PERFORMANCE ASSESSMENT OF RETROFITTED SRC GIRDERS USING CHMC
TO DISSIPATE INELASTIC ENERGY
Fatigue Crack
Encased Steel (W-Section)
Fracture of Tensile Rebar
Repair and retrofit of Severely Damaged Steel-Reinforced Concrete (SRC) Girders
0 25 50 75 100 125 1500
100
200
300
400
500
600
700
Load
(K
N)
Deflection (mm)
B1 (CarbonFlex Retrofitted SRCC Beam)
0 25 50 75 100 125 1500
100
200
300
400
500
600
700
Deflection (mm)
B2 (CFRP Retrofitted SRCC Beam)
0 25 50 75 100 125 1500
100
200
300
400
500
600
700
Deflection (mm)
B3 (CarbonFlex Retrofitted SRCC
Beam with No Steel Welded)
B1 B2 B3
FLEXURAL LOAD TESTS – INELASTIC ENERGY DISSIPATION OF RETROFITTED SRC GIRDERS
68% of the peak load is sustained at tremendous ductility
following fracture of the welded encased steel at about 550kN
B1 – SRC Retrofitted by CHMC B2 -- SRC Retrofitted by CFRP
SEISMIC DESIGN OF OPEN-FRONT WOOD-FRAMED
STRUCTURES USING CONVENTIONAL PLYWOOD
WALLS Traditional as-is wood-home designed according to code using
plywood sheathing for shear wall construction (quasi-dynamic tests)
Displacements and accelerations are large
Nails are shown to either pop-out or withdraw from plywood sheathing
• Detachment of sheathing
• Issues of soft-story damage and insufficient force transfer
CHMC is used in shear wall construction of wood-framed structures
under quasi-dynamic loading in lieu of traditional plywood panels
Reduction of displacements and accelerations via energy-dissipation
R-factor (Response Modification Factor) increases from 6.5 (traditional
plywood sheathing) to 8.185 (CHMC sheathing)
Permit efficient story force transfer and limit soft story collapse
SEISMIC TEST RESULTS OF OPEN-FRONT
WOOD-FRAMES DESIGNED USING CHMC
SHEAR WALLS
Development of a next-generational structural composite for
extreme-load protection
“Across-the-board” pervasiveness
Advent of “tunable” properties is vehicled through dual polymeric
hybridization and material parameterization
The following properties are controlled:
Impact resistance
Damping
Fracture toughness
New three-year project has been awarded
CONCLUSIONS
SELECTED RELATED PUBLICATIONS
Zhou, H. and Attard, T.L. (2012). “Rehabilitation and strength sustainability of fatigue
damaged concrete-encased steel flexural members using a newly developed polymeric
carbon-fiber composite,” Composites Part B: Engineering, 45, 1091 – 1103.
Zhou, H., Attard, T.L., Wang, Y., Wang, J.A., and Ren, F. (2013). “Rehabilitation of
notch damaged steel beams using a carbon fiber reinforced multiphase-matrix
Composite,” Composite Structures, 106, 690 - 702.
Zhou, H., Dhiradhamvit, K., and Attard, T.L. (2014). “Tornado-borne debris impact
performance of an innovative storm safe room system protected by a carbon fiber
reinforced hybrid-polymer matrix composite,” Engineering Structures, 59, 308-319
Zhou, H., Attard, T.L., Zhao, B., Yu, J., Lu, W., and Tong, L. (2013). “Experimental
study of retrofitted reinforced concrete shear wall and concrete-encased steel girders
using a new CarbonFlex composite for damage stabilization,” Engineering Failure
Analysis, 35, 219–233
THANK YOU FOR YOUR ATTENTION
0 100 200 300 400 5001E-5
1E-4
1E-3Velocity Response as a function of frequencyPower Spectrum Density
Frequency f (Hz)
Velo
cit
y v
(f)
(m/s
)
1E-9
1E-8
1E-7
1E-6
Po
wer
December 12, 2014
FOR ADDITIONAL QUESTIONS