Plastics News Europe - September 2019 - 18

additive manufacturing

ded on target for 3d
printing composites
A process developed by Arevo for the 3D printing of carbon-fibre reinforced
composite materials enables the manufacture of strong and lightweight
parts for end-use applications. The technology promises to be a gamechanger for producing structural parts from composite materials, according
to Dr Natalie Rudolph, VP of R&D, Arevo

hile the use of 3D printed
metal parts in structural applications is increasing at a
rapid rate, plastics have not had the
same success. As currently one of the
fastest-growing areas in manufacturing, Additive manufacturing is opening up a host of new opportunities
for the design and production of
parts. However, developing structural
plastic parts based on AM technology
has proven to be a challenge, as few
materials and processes provide sufficient durability for this purpose.
One of the problems is related to
the lack of reliable material data for
design as well as missing component
level tests. At the same time, measuring this data for faster and improved
product design is only viable for processes that are suitable to produce
end-use parts. In addition, the anisotropy of almost all AM parts makes
the required testing programmes
much more extensive than for other
processes that yield more isotropic
material properties. Therefore, efforts
to standardise tests and obtain high
fidelity data sets are progressing
slowly and are very expensive. As a
result, simulation efforts are progressing at slow speeds and often cannot
be validated with experimental data.
As a consequence, the confidence
level with using plastic AM parts has
remained low.
California-based Arevo has now
developed a process called polymer
Direct Energy Deposition (DED) to address this challenge. DED is a wellknown method for metal additive
manufacturing, yielding fully dense
parts with final material properties
similar to those of wrought material.
The process involves feeding a metal
feedstock - a powder or wire - into
the path of a laser or electron beam
to be fused by melting as the material
is deposited.
Now, something similar is available that enables the automatic printing of continuous fibre-reinforced
composites. "Polymer DED technology allows the processing of carbon

'The Plant', Arevo production area

fibre volume contents of greater than
50 percent, for the utmost in strength
and flexibility, and incorporates advanced modelling and software capabilities," says Arevo.
To understand how DED compares
to existing processes and the significance of this development for manufacturing, first some background information about composites in
general.

Fibre-reinforced composites
- what are they?
Composite materials are a distinctive
set of materials, characterised by the
combination of individual components to achieve an enhanced material, which exceeds the capabilities of
the separate elements. In their most
general form, composites are the result of embedding particles of one
material in a surrounding matrix comprised of another material. The combination of the particles with the matrix produces a favourable mix of
properties that cannot be achieved
with either of the constituents acting
alone.

There are many types of composite materials. The shape and dimensions of the reinforcing phase strongly affect the mechanical properties of
the composite. In general, therefore,
composite materials are classified
based on the geometry of the reinforcement.
When fibres are used as the reinforcing phase, they provide strength
and stiffness to the finished composite part. The polymeric matrix binds
the fibres together, transfers the load
from the matrix to the fibres, and protects the fibres from abrasion and the
environment. The load is transferred
at the interface of the matrix and the
fibres and, thus, the interfacial bond
between the constituents determines
the mechanical properties and performance of the composite.
Fibre-reinforced composites can
be divided into subcategories based
on the length of the fibres and associated orientation state of the fibres.
The first distinction is between discontinuous and continuous fibre
composites. Furthermore, discontinuous fibre composites are categorised

september 2019

Plastics News Europe - September 2019

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