Advanced Materials

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.

Objective

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.

Approach

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.

Tools Used

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)

Benefits Provided

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

Past Experience

Joint Publications with key Aerospace Industry and University Partners:

Honeycomb Structure

Ceramics