CASE STUDY:
CARBON
FIBER
MACHINE
TOOLING

MNTFs Nanoparticle Additive enhanced carbon fiber composite was first developed for machine tool holding. Machining is a very hot, sometimes chemically active environment, where the pressure and rotational speeds are extreme. Cutting forces are causing flexural, torsional and tensile stresses in the tool, causing vibration tool deflection and lack of stability in holders.

In the aggressive environment of machining, where lightweight is normally not a factor, the MNTFs Nanoparticle Additive enhanced carbon fiber composite is out-performing steel and surpassing the performance of tungsten carbide in deflection properties.

The obvious application for a material with this level of deflection and modulus properties is aircraft wings, but there is also a good probability that the MNTFs Nanoparticle Additive enhanced carbon fiber composite could be used for automotive and aircraft parts that until now have been reserved for other materials than carbon fiber composites.

OUT-PERFORMING STEEL.
SURPASSING TUNGSTEN CARBIDE
IN DEFLECTION PROPERTIES.

ADDRESSING PROBLEMS OF FORCES
INVOLVED IN MACHINING.

MNTFs Nanoparticle Additive enhanced carbon fiber composite vibration dampening tool holders and quills are addressing the problems of the forces involved in machining and is evidence of the crucial importance of complete tool solutions for the overall production economy. Despite the fact that machine tools represent a small part of the total production, the right tool solution result in cost savings of up to 20% of the total cost. Reduced environmental impact and lower total cost is driving demand for highly effective tool solutions.

A cutting tool is made up of a cutting edge and a holder. During machining, the cutting edge wears out in matter of minutes as the service life is considered to be over. Cutting edge service life is defined as the effective production time during which the cutting edge can be used in machining of components and pass specified tolerances. It is of paramount importance that it’s possible to predict the theoretical cutting edge service life with great confidence, as most processing is done in machines destitute of monitoring or even supervision. Extended processing past the service life of the cutting edge invariably leads to insert failure or breakdown. Selecting the appropriate cutting edge is critical in obtaining maximum productivity in processing.

It is imperative to get everything right in a very hot, chemically active environment where the pressure and rotational speeds are extreme. The cutting forces are causing flexural, torsional and tensile stresses in the tool, causing vibration, tool deflection and lack of stability in holders and clamping. These are the contributing factors that shorten the service life of the cutting edges. So far, the best available technology has been to use steel for holders of cutting tools, or carbide for applications where stiffness is paramount. The high tensile modulus of carbide reduces tool deflection, but its high weight means that the eigenfrequency rate is lowered, which may result in additional vibration problems. To avoid excessive wear of the cutting edges resulting in problems such as poor surface finish; insufficient accuracy; increased wear of machine tools; and high noise level, the cutting forces must be restrained, leading to inefficiency and costly productivity losses.

MNTFs Nanoparticle Additive enhanced carbon fiber composite has a density of 2,1 g/cm3.
The MNTFs Nanoparticle Additive enhanced carbon fiber composite vibration dampening tool holder has a specific stiffness which is 7,5 times that of steel.
The MNTFs Nanoparticle Additive enhanced carbon fiber composite vibration dampening tool holder reduces the maximum tool deflection to 2 mm at 200 000 rpm.

FRACTURE
TOUGHNESS
BY
INTERFACE
CONTROL.

FRACTURE TOUGHNESS NEED

Carbon fiber composites occupy an ever-growing niche in aeronautical engineering, demonstrating outstanding performance of strength and stiffness. However, a negative consequence of the dense crosslinking that enables adhesion to the reinforcing fibers, cohesive strength and low shrinkage in the cured state is the fragility of the matrix. Consequently, layered carbon fiber composites observe low fracture toughness in the direction of the orientation layers and between them. The primary form of damage caused by the fragility of the matrix is the development of cracks.

MNTFs NANOPARTICLE ADDITIVE STRUCTURING APPROACH

The priority in the construction of composite materials is to control the interfaces, to neutralize the excitation energy, to meet different levels of potential and to minimize the free energy level of the system.

Fracture toughness of carbon fiber composites with a thermosetting matrix is the ability to resist fracture during accumulated structural changes of extended influence of mechanical stresses and environmental factors. The rate of accumulation of damage indicates the need to improve the composition and structural state of the polymer matrix.

The major concern are the irreversible destruction processes in the polymer matrix at the carbon fiber/matrix interface. Deformed carbon fibers generate a non-equilibrium synergetic system that aims to utilize the most effective channels of dissipation of elastic energy. Inhibition of these processes or making them reversible is essential.

The solution is to improve the level of plastic deformation of the epoxy matrix in front of the advancing shock or fatigue crack, increasing the binding energy as well as the adhesive strength at the carbon fiber/matrix interface.

MNTFs NANOPARTICLE ADDITIVE BENEFIT

MNTFs Nanoparticle Additive structuring changes rheology and morphology of the epoxy matrix, deformability of the gel-phase, and elastic deformation properties of the cured polymer.

The interface control is managed by the patent-protected MNTFs (Multi-layer carbon nanoparticle of toroidal form) Nanopartcle Additive which is added to the matrix. The interface control phenomenon is triggered by the presence of a closed network of delocalized π-electrons in the MNTFs Nanoparticle Additive and is most pronounced at the interface regions, where the amplification of the electromagnetic field by several orders of magnitude (up to 3×104) is modifying the van der Waals interactions, which in turn is affecting polymerization and crystal formation processes in the inorganic systems of the carbon fiber composite.

At the carbon fiber/matrix interface a 10 microns thick interfacial layer of perpendicular oriented polymers is formed (Fig. 1.). This formation and the more homogeneous supramolecular structure of the matrix provide increased interface density and fracture toughness to the carbon fiber composite, as the possibility of composite crack initiation at the critical interface is restricted.

MNTFs Nanoparticle Additive structuring provide giant resonance in the electromagnetic field which binds free energy in structural defects like nanoscale fractures or cracks, which in turn contributes to overall stability of the system and increases its resistance to external loading.

In conclusion, MNTFs Nanoparticle Additive structuring effectively acts as inhibitor of microcracks and nanoscale conductive elements with increased transverse conductivity, improved heat capacity of the composite, ability to absorb external energy and enable scattering of thermal and power loading. Through the organization of the nano-level system of stoppers of microcracks as well as boosted dissipation ability, fracture toughness of carbon fiber composites is increased.

Fig. 1. SEM image (x2000) of interfacial layer

TAMING
THE DELAMINATION
DEMON

The MNTFs nanoparticle additive addresses the problematic failure modes of unmodified carbon fiber composites of which delamination is the most destructive type of defect that can occur.

Delamination can overhaul the structural integrity of the composite by reducing compressive strength and mechanical stiffness. In a worst-case-scenario, delamination may propagate and cause irreversible damage in the form of fracture to the composite.

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