Composite materials with viscoelastic stiffness greater than diamond

Area of Science:

• Materials Science
• Solid Mechanics
• Composite Materials

Background:

• Conventional composites have properties bounded by constituent properties.
• Achieving a modulus greater than the stiffest constituent is typically not possible.
• Barium titanate inclusions exhibit volume-change phase transformations when unconstrained.

Purpose of the Study:

• To demonstrate composite materials with a viscoelastic modulus significantly exceeding their constituents.
• To investigate the mechanism behind achieving a modulus greater than diamond.
• To explore the role of constrained barium titanate inclusions.

Main Methods:

• Fabrication of composite materials with barium titanate inclusions in a metal matrix.
• Mechanical testing to measure viscoelastic modulus and strength.
• Analysis of the phase transformation behavior of barium titanate under constraint.

Main Results:

• The composite material exhibited a viscoelastic modulus substantially greater than either the metal matrix or barium titanate.
• The composite's modulus surpassed that of diamond, though its strength did not.
• Constraining the barium titanate inclusions stabilized their negative bulk modulus.

Conclusions:

• Composite materials can be engineered to possess a modulus far exceeding constituent properties.
• Stabilized negative bulk modulus in inclusions is a viable mechanism for creating high-modulus composites.
• This approach offers a novel pathway for designing advanced materials with superior mechanical properties.