Challenges in Composite Materials Research for Lightweight Structures
Ramesh Talreja Tenneco Professor
Department of Aerospace Engineering Department of Materials Science and
Engineering Texas A&M University
Content
• Lightweighting with composite materials
• Current status and roadblocks
• Remedies for way forward
• Challenges and opportunities
• Conclusions
What is lightweighting?
Lightweighting is the engineering process of reducing the weight of products, components, and systems for the purpose of enhancing
(1) performance, (2) operational supportability, and (3) survivability.
It entails
Design, development, and implementation of lightweight materials and technologies.
Engineered Lightweighting with Composites
• Creative fiber architecture (coupled response, multifunctionality)
• Cost-effective manufacturing (effects of defects)
• Physics based failure analysis (beyond “strength” criteria)
• Integrated computational materials engineering (ICME)
Defect-Damage Mechanics
• Fiber Defects
Misalignment,
waviness
Breakage
• Matrix Defects
Incomplete curing
Voids
• Interface Defects
Fiber/matrix disbonds
Delamination
• Fiber volume
fraction
• Fiber
Distribution
Length
Orientation
Idealized models:
Heterogeneities,
no defects
Real composites:
Defects
8
Voids induced by irregular manufacturing
Voids caused by dissolved moisure In resin (Grunenfelder & Nutt, CST, 2010)
Voids caused by not applying vacuum (Huang, et al., 2011)
13
Defect-damage mechanics Case studies
• Effect of voids on elastic properties (H. Huang, R. Talreja)
• Effect of fiber clusters on crack initiation in short fiber composites (H. Huang, R. Talreja)
• Effect of voids on crack growth in woven fabric composites (M. Ricotta, M. Quaresimin, R. Talreja
• Effect of defects on damage progression in laminates (Y. Huang, P. Carraro, M. Quaresimin, J. Varna, R. Talreja)
Defect-damage mechanics Case studies
• Effect of voids on delamination growth under compression (L. Zhuang, R. Talreja)
• Effects of voids and interfacial disbonds on failure of joints (C. Chen, R. Talreja)
• …..
Failure in Multi-axial Fatigue
Global loading is MULTIAXIAL However, Local failure is in BIAXIAL stress state
Gravity forces
Aerodynamic forces
Combined forces
Laminated composite
Current state of multi-axial fatigue
• Most current approaches are essentially modified “metal fatigue”, lacking THINK COMPOSITES content.
• Schemes, formulas, ad-hoc ideas with poor, uncertain predictive capability.
References: • Fatigue behaviour and life assessment of composite laminates under
multiaxial loadings, M. Quaresimin, L.Susmel, R. Talreja International Journal of Fatigue, 32 (2010) 2–16
• M. Quaresimin, R. Talreja “Fatigue of fiber reinforced composites under multiaxial loading” in Fatigue life prediction of composites and composite structures, A.Vassilopoulos Ed. , 2010 Woodhead Publishing Ltd,, 2010, p. 334-389.
Failure criteria adopted from metals
• Tsai-Hill criterion (metal plasticity)
• Smith-Pascoe crierion (metal crack growth)
• Fewaz-Ellyin criterion (S-N curve based)
Prediction by Fewaz-Ellyin criterion
10
100
1000
10000
100000
1000000
10000000
10 100 1000 10000 100000 1000000 10000000
Nf,e [Cycles]
Nf [C
ycle
s]
G, R=0.1H, R=0H, R=0.5H, R=-1I, R=0.1K, R=0.1 (W)L, R=0.1L, R=0.3-0.5L, R=-1M, R=0.1
Non-Conservative
Conservative
Roadblocks
• Current failure analyses are empirical, semi-empirical, or phenomenological
• Manufacturing and performance assessment processes are disconnected
• Cost considerations are mostly limited to acquisition cost
Remedies, directions for future research
Remedy #1: Multi-scale approach. Need to go to levels below the homogenized composite. That’s where the action is.
Remedy #2: Constraint analysis. Need to look at lamina (UD composite) failure within the constrained environment of a laminate.
Remedy #3: Defect mechanics. Need to consider defects. They are the initiators of failure.
Way forward: Remedy #1 multi-scale analysis
Tensile stress
Shear stress
2
3
1
fiber
matrix
Investigate the failure process at the fiber/matrix scale under imposed (homogeneous) ply level stresses. Model that failure process in terms of the ply stresses. Competing failure processes occur depending on the local stress state.
Way forward: Remedy #1 multi-scale analysis
5 55
𝜎
Load
ing
dir
ecti
on
Near the 0° ply at the free edge ((y, z)=(W, h))
Central plane of the free edge ((y, z)=(W, 0))
Internal section ((y, z)=(0, 0))
Cracking positions
W
1/8
model
h
(y, z)=(0, 0)
L
Lxx
0°pl
y
90°ply
Resin
x y
z
Macro
Micro
Way forward: Remedy #2: Analyze constrained ply cracking und
Fiber/matrix debonding Single crack formation
Multiple Cracking
Lamina within a laminate
Fiber bundle within a woven fabric composite
PROGRESSIVE FAILURE CAUSED BY CONSTRAINT
Integrated overall strategy (including Remedy #3)
Matrix dominated
failure
Fiber dominated
failure
Damage Threshold Behavior
Effects of Manufacturing Defects
Lamination constraints
Interlaminar failure
Failure criteria
Structural analysis
and design
Looking further out in the future
The Big Picture
Materials Characterization
Stiffness, Strength, Toughness
Life Cycle Cost Analysis Cost/Performance Trade-offs
Performance Evaluation
Durability, Damage Tolerance
Manufacturing
Process Modeling & Simulation
Tooling, Machining, Assembly
The sustainability dimension
The design of materials, processes, products and systems should sustain good conditions for human health
and environment
PLANET
EARTH
Resources
Materials/Energy
Products/
Processes
Reuse/
Recycle
Waste
PLANET
EARTH
Resources
Materials/Energy
Products/
Processes
Reuse/
Recycle
Waste
Conclusions – challenges and opportunities Lightweight engineering with composite materials can
produce high performance, cost-effective structures
Current failure models must be improved by multi-scale
laminate based analyses incorporating manufacturing
defects
Looking further in the future, cost analysis should be
expanded to life-cycle cost
Sustainable composite design will require more advanced
design concepts such as design for disassembly,
reuse/recycling and life cycle assessment.