Multifunctional Ceramic Matrix Nanocomposites Manufacturing
We developed a novel technique for manufacturing lightweight ceramic matrix
composites (CMC). This technique is based on a recently developed polymer-derived ceramic
(PDC) processing, in which ceramics are synthesized by thermal decomposition of polymeric
precursors, instead of by sintering ceramic powder compacts. Figure 1 schematically illustrates
the basic steps of the proposed technique, including: (1) synthesizing a preform with the desired
dimension and microstructure from carbon nanotubes, (2) infiltrating the preform with a liquid
phase polymeric precursor, (3) solidifying the precursor to form a fully-densed polymer-based
nanocomposite, (4) machining the nanocomposite into the desired shape and surface quality, and
(5) pyrolyzing the machined polymer nanocomposite to obtain the final ceramic nanocomposite.
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Figure 1: Schematic showing the basic steps for making ceramic matrix composites.
One example is a low cost manufacturing method to improve the interlaminar tensile
strength for fiber-reinforced material in high temperature and extreme environment. The
typically poor interlaminar tensile strength (ILT) of high temperature material system containing
2-D woven fibers imposes limits on the design of hot section components. New material system
is needed to lower the expense of over-built components, particularly for hot structure aeroshell.
The proposed manufacturing method to embed CNTs along the vertical direction within each
fiber bundle, would not only help improve the design limits, but also improve the interlaminar
tensile strength (ILT) for current material system. As shown in the SEM pictures, there is carbon
fiber pull-out phenomenon on fracture surface and CNTs have good dispersion in the matrix. The
material characterization results are:
• Mechanical Property: According to the three-point bending strength test, with the
inclusion of CNTs, the strength of 3-dimensional reinforced ceramic composite increases
26% than that of 2-dimensional one. Therefore, the required thickness can be reduced
significantly. The associated material cost and manufacturing cost can be minimized.
• Electrical Property: The electrical conductivity (along in-plane direction) increases 25%.
• Thermal Property: the thermal conductivity (along z axis) increases 10%. This enables
to dissipate heat quickly to cooler zone, and the life time of the material system is
extended substantially.
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CNTs are aligned along the vertical direction to ensure the 3rd-dimensional bonding strength.
Carbon nanotubes (CNTs) are reinforced along
the vertical direction in between of each
carbon fiber bundle
CNTs
CNT/PDC
Cf
CNT/PDC
Cf
PDC
(a) surface area (x-y plane);
polished surfaces
Cf
(b) cross-section area (vertical plane);
fracture surface
Stack of multiple layers of carbon fiber sheets
(Patent applied)
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In summary, the advantages of such manufacturing method are summarized as below:
Low cost, and the manufacturing procedure can be scaled up in size.
This manufacturing process can produce parts with curvatures or other complex
geometries.
The volume fraction of the fiber reinforcement and CNTs reinforcement can be adjusted
based on design needs. In our experiment, the volume fraction of Carbon fiber is 45
Vol.% and that of CNTs is 10 Vol.%.
This manufacturing process is generic – can be applied to different types of fiberreinforced high temperature material systems.
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