30 Jun 2010   |   News

ETH Zurich: Lighter and stronger reinforced composites

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Researchers at ETH Zurich have developed a method for using magnetic nanoparticles to control the orientation of reinforcing particles in polymer-based composite, resulting in improved properties in the resulting material.

In the process, small quantities of magnetic nanoparticles (below 0.01% by volume) are temporarily attached to the reinforcement particle of interest. The reinforcing particle is then combined with the polymer precursor material, which is subsequently cross-linked or solidified. A low-strength magnetic field is then applied to orient the reinforcing particles.

The surprisingly low magnetic fields required to achieve orientation allow for the use of conventional, cheap magnets to achieve platelet alignment. After the matrix is consolidated, the magnetic nanoparticles can be removed without effect on the reinforced composites.

Composite materials with reinforcing particles embedded in a matrix material are extensively used in construction, aerospace, automobile and medical industries.

These composites employ continuous or discontinuous fibres to reinforce polymeric matrices. Though this reinforcement enhances the mechanical strength and stiffness of the matrix, it is limited to one specific direction. 3-D reinforcement remains challenging due to the limited control of particles in the out of- plane direction.

Features and benefits of the ETH method include:

  • a 10-fold increase in compression stiffness perpendicular to the film surface resulting in highly improved material properties;

  • Coatings with a 10-fold smaller out-of plane thickness;

  • Low magnetic fields of 0.001 –0.01 Tesla are required for alignment and a low magnetic nanoparticle content is sufficient to induce this effect

  • There is fine control, making it possible to locally reinforce regions of high stress concentration. This will provide a wider range of options in component design.

Applications include:

  • Advanced composites with enhanced delamination strength

  • Polymer coatings with increased compression stiffness perpendicular to the surface

  • Flaw-tolerant advanced composites

  • Scratch resistant coatings and laminates

A patent is pending (EP Ref. No. T-10-021)

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