Conventional fiber reinforced composite materials exhibit higher specific stiffness
and strength than ones exhibited by traditional metal materials. Applications of composite materials
lead to weight reduction and energy savings. The matrix system usually a polymeric, ceramic,
or a metallic material. The properties are tailorable in plane; however, further enhancement
is possible by creating a sandwich material system like fiber metal laminates, honeycomb and
foam core, and even by reinforcing the matrix material using nano-materials (e.g., nanotubes,
nano-fibers, silica particles, etc.,) and chopped fibers. Engineers also may use 3-dimensional
stitched, braided or fabric materials. Performing durability and damage tolerance analysis on
structural components made of such advanced composites material systems is a difficult task
as range of stiffness, Poisson's ratio and strength properties are desired for such analysis.
The challenge comes from difficulty in performing reliable mechanical tests on nano-materials
in a less expensive way.
It is highly desirable to be able to simulate structural components made of these
advanced materials subjected to static, fatigue or impact loading conditions. It is also desirable
that the simulation be done without any extensive finite element modeling or several expensive
coupons level test data. Recall that usual finite element approach requires extensive modeling
efforts whereby the engineer models all the constituents without knowledge of complete set of
mechanical material properties, or homogenized model ignoring any possible fiber matrix level
root cause issues.
Since in advance complex material systems the root cause for damage initiation is the
constituents, it is vital that constituent level damage evolution be accounted accurately during
the load increment without extensive modeling efforts. We recommend the following approach for
simulating such problems:
Characterize the in-situ linear/nonlinear constituent material properties obtained using
simple flat coupon test data
Perform D&DT analysis using less extensive finite element models combined with progressive
failure and advanced 3 dimensional micro-mechanics theories at each incremental loading to evaluate
the damage progression at the constituent level.
Material characterization is done using the following tools:
Conventional composites (PMC, CMC, MMC): Material Characterization & Qualification (MCQ)
Nanocomposites: MCQ Nano
Metals: Fracture Toughness Determination (FTD) and Fatigue Crack Growth Curve (FCG)
Reduce constituent level testing using expensive scientific tests, for example, Atomic Force Microscope.
Generate scatter at laminate level by virtually introducing the variation in material properties
Reverse engineer the constituent properties.
Provide guidelines for improving material behavior.
Identify root cause problems for D&DT analysis without extensive FE models
Joint Publications with key Aerospace Industry and University Partners: