JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 25

Will composites be competitive with metals in 3D printing?

Focus
Mantis Composites, a startup company
close to having the first carbon fibre 3D
printer that can produce fully functional
composite parts with continuous fibres
in 5 axes, is currently seeking strategic
partners and investors interested in the
performance that could be realized with
their solutions.

continuous fibre process. But researchers
have shown that their filament has large
voids and contains many resin-rich areas,
resulting in substantially lower properties than the rule of mixtures would suggest - their unidirectional coupons just
barely surpass 6061 aluminium in tensile
strength. Plus, the combination of porosity and printing parallel layers rather
than multiaxial printing results in poor
interlaminar and fatigue properties leading to delamination and matrix cracking.
Markforged has effectively targeted their
product to the consumer market, offering
a safer and more manageable alternative
to CNC machining aluminium at home,
but this solution (especially when considering the $500/lb+ price point for their
filament) is difficult to justify outside of
the home, workshop or makerspace.
Mechanical performance only gets lower
from here. Enter discontinuous carbon
fibre 3D printing, a process that currently
yields low properties since the fibres are
so short they pull out of the matrix rather
than reinforcing up to fibre failure. The
minimum length to have the fibre rupture
rather than slip is known as the critical
length. Although chopped carbon fibre
feedstock is available for SLS applications, the powder morphology limits fibre
length. Impossible Objects has developed
a process that involves stacking layers of
carbon fibre tissue-paper-like material,
and pressing those together. This uses
somewhat longer fibres, but it is expensive and achieves comparable performance to SLS.
Fused deposition modelling
Fused deposition modelling (FDM) printing could theoretically achieve longer fibre
lengths, but all current solutions have fibre
lengths about an order of magnitude lower
than the critical length. Regardless, it is

still an interesting area. Arevo Labs is one
of the companies currently offering fibrereinforced FDM with high-temperature
thermoplastics. The current processes for
making FDM filament are adapted from the
same sort of screw extruders that are used for
injection moulding, and this process always
breaks down carbon fibres well below their
critical length. Therefore, when Arevo adapted this process to the intrinsically stronger
PEEK, they did get some improvement,
but not enough to bring the true strength of
composites to their parts. Arevo's parts have
roughly double the tensile strength and four
times the modulus of PEEK plastic alone.
In comparison, Cytec's ACP-2 PEEK (intermediate modulus), a prepreg composite
material commonly used for automated tape
laying, has 40x the modulus and 30x the tensile strength of neat PEEK. That is a large
performance gap. Arevo Labs uses a multiaxis robotic arm instead of a simple 3-axis
printer, which allows them to develop parts
more tailored to the strength needs of their
customers, but higher mechanical properties are needed to achieve the full value of
that system. Besides, their high cost (higher
than Markforged) further detracts from use
in a production setting.
Potential methods
However, there are still potential methods
for higher performance 3D printing with
short fibres. Given how short all the fibres
are in these processes, any company that
could develop a filament for FDM with
high-temperature thermoplastics and carbon fibres with an average length closer to or
above the critical length could achieve substantially higher properties at a reasonable
cost, opening up many new opportunities.
Despite the current limitations, it is important that efforts are being made towards
making carbon fibre 3D printing work.
Large amounts of money are being invested
into proven metal 3D printing technologies, but far less money is going towards
developing the so far unproven concept of a
true carbon fibre 3D printer. With metal 3D
printing, existing companies are focusing
on developing this cutting edge technology,
whereas composite 3D printing advancements are coming almost entirely from
smaller startups with disjointed approaches.

Fig. 2: Carbon fiber 3D printing could bring high
performance and complexity

Some of the approaches suggest paths towards improvement - short fibres can be
made longer, multi-axis printing machines
can be developed that target a low cost per
print time for parallel manufacturing, and
continuous fibres need to be effectively wetout and oriented.
Sporadic effort
Incremental improvements are not what allowed the metal industry to develop the 3D
printing technology they have - it was the
significant investments into a technology
that had the potential to be a serious gamechanger. Alcoa's yearly revenue is roughly
the same as the entire carbon fibre composites market, and their investment is focused,
whereas the composite industry often
makes sporadic efforts towards short-term
objectives that do not usually span across the
entire industry. The model of playing catchup eventually works, but why not gain the
definitive edge and maintain the lead? This
can be achieved, to the benefit of the composites industry and its customers, by systematically engaging and pursuing new risky
technologies, even if those technologies are
not being developed in-house and still need
maturation. Composites may very well be
the material of the future, but 3D printing
is the manufacturing method of the future,
and until the two are combined in an effective, inexpensive, and scalable method, the
ease of use presented by metal will continue
to prevail.

No108 October 2016

More information:
mchapiro@mantiscomp.com

/ jec composites magazine

25



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #108 - October 2016

Cover
Edito
Opinion: BOI Thaïlande
Contents
NEWS
In brief
Agenda
JEC Conferences 2017
BUSINESS
Merging
Basalt
MANUFACTURING
Biocomposite
Green Materials
3D Printing
Feature Wind energy RECORD BEATING INDUSTRY
Resin
Performance
Recycling
Recycling
Offshore
Process
Design
Market
SOLUTIONS
Marine
Infrastuctures
Construction
Pavilion
In the world
TECHNOLOGY
Simulation
Repair
Index
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - BckCovAd
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Opinion: BOI Thaïlande
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - In brief
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Ad2
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Agenda
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - JEC Conferences 2017
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 12
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Merging
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 14
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Basalt
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 17
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 18
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Biocomposite
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Green Materials
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 23
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 3D Printing
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 26
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Resin
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 29
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Performance
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Recycling
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Recycling
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Offshore
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 36
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Design
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Market
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 40
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Marine
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 43
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Infrastuctures
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Construction
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Pavilion
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Simulation
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 53
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Repair
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 57
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #108 - October 2016 - 59
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