JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 64

TECHNOLOGY multi-material
The shear stress at the interface can be taken as a guidance
for checking the adhesion between these two materials,
eliminating the need for specific mechanical modelling,
except to check for proper process parameters in a process
simulation.
A predictive methodology was established in two commonly
used commercial software platforms, Abaqus and LS-DYNA,
and in both implicit and explicit numerical schemes to ensure
that the methodology can be used for a wide variety of market
segments, use cases and customer organizations.
All the necessary physics details were modelled while selecting
the respective material models, as explained below.
For UD tapes, the density and direction-dependent elastic
properties are the first required parameters.
Then, detailed damage initiation and propagation properties
in different material directions need to be defined.
The selection of damage initiation criteria is a key
consideration at this stage.
The evolution of damage and ultimate rupture through damage
propagation are defined in the material model through either
rupture energy, ultimate damage displacement or strain, along
with an evolution-softening behaviour depending on the
commercial software.
It is extremely important to understand the rupture behaviour
for both the fibre and matrix, in both tension and compression,
to be able to define the necessary rupture properties.
Additionally, since various types of software need inputs
in different formats, it is important to ensure that the right
conversions are made and sign conventions are maintained for
behaviour equivalence.
Sometimes, there is an interrelation between fibre and matrix
failures, which are also considered.
For overmoulded long fibre thermoplastics, density and elastic
properties are the first material properties to be defined.
These materials should be modelled as anisotropic
materials with fibre orientations derived through processing
simulations.
However, transversely isotropic modelling may be adequate
for initial simulations.
Then, post-yield strain hardening is defined through the
yield stress/plastic strain curves. For use in impact and crash
simulations, these data are characterized at different strain
rates and input in the material model.
Damage initiation, dependent on both strain rates and
stress tri-axiality, is defined in the material model. It is very
important to model a realistic material behaviour. Stress triaxiality defines the state of stress and can be easily understood
from Figure 4.
Any state of stress is a combination of a hydro-static stress
component (pressure, p) and a deviatoric component (vonMises stress, q), as illustrated in the figure.
The ratio of p over q is called the stress tri-axiality factor, k.

64

jec composites magazine / N°121 May - June 2018

The following values of k define different states of stress:
-

k=0, pure shear
k=-1/3, uniaxial tension
k=-2/3, biaxial tension
k=1/3, uniaxial compression

As can be seen from Figure 4, the von-Mises yield surface is not

Fig. 4: Example of a damage initiation surface as a function
of stress tri-axiality (PVC)

accurate in predicting damage initiation for stress states other

Fig. 5: Effects of including damage physics

than uniaxial tension. For a representative thermoplastic (PVC)
for which tested values are available [1], damage initiation stresses
in uniaxial compression, pure shear and biaxial tension are all
different than uniaxial tension. Hence, it is important to account
for different failure stresses for different states of stress. This is
crucial for a realistic prediction of a part behaviour. It is also
important to remember that different software treat the sign
convention for the state of stress differently, and this needs to be
addressed during the material model definition. The last point
to be addressed when modelling overmoulded plastics is the
modelling of damage evolution. Similar to UD tapes, this is defined
through either displacement, strain or rupture energy. Note that



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #121 - May 2018

Cover
Edito
Opinion: Lighter, faster, smarter
Contents
NEWS
In brief
JEC World 2018 Report
JEC World 2018 gathered the whole composites industry in Paris
JEC innovation Awards Winners 2018
Startup Booster - A springboard for innovative talents
Injection - lnjection moulders who have made bioplastics work
Agenda
BUSINESS
Acquisition - Huntsman acquires Nanocomp Technologies
Simulation - "We want to bring the story of composites to the end user in a different way"
Trends - Overview of the North Amaerican composites market
MANUFACTURING
Additive manufacturing - The Energica dashboard reinvinted through professional 3D printing and composite materials
Prototyping - Injection moulding: running tests earlier with 3D printing
Mass-production - Fast RTM: a techincally and economically optimised solution
Covers - Opportunities for composite profiles in the residential housing market
SOLUTIONS
Building - CompoHouse, the demonstration building made of composites
Construction - Textile concrete makes thin, large-sized curtain walls possible
In the world
TECHNOLOGY
Multi-material - High-confidence performance predictions for hybrid thermoplastic composite applications
Experimental techniques - 3D tectile-reinforced composites: from manufacturing to structural design
Index
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JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Cover
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 2
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Edito
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Opinion: Lighter, faster, smarter
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 5
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Contents
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 7
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - In brief
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 9
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - JEC innovation Awards Winners 2018
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 11
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 12
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 13
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 14
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 15
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 16
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 17
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 18
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 19
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Startup Booster - A springboard for innovative talents
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Agenda
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 22
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 23
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Acquisition - Huntsman acquires Nanocomp Technologies
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 25
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Simulation - "We want to bring the story of composites to the end user in a different way"
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 27
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Trends - Overview of the North Amaerican composites market
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 29
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Additive manufacturing - The Energica dashboard reinvinted through professional 3D printing and composite materials
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 31
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Prototyping - Injection moulding: running tests earlier with 3D printing
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 33
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Mass-production - Fast RTM: a techincally and economically optimised solution
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 35
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 36
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 37
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 38
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 39
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 40
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 41
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 42
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 43
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 44
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 45
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 46
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 47
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Covers - Opportunities for composite profiles in the residential housing market
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 49
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 50
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 51
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 52
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 53
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 54
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 55
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Building - CompoHouse, the demonstration building made of composites
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 57
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 58
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Construction - Textile concrete makes thin, large-sized curtain walls possible
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - In the world
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 61
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Multi-material - High-confidence performance predictions for hybrid thermoplastic composite applications
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 63
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 64
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 65
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 66
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Experimental techniques - 3D tectile-reinforced composites: from manufacturing to structural design
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 68
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 69
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - Advertisers
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 71
JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 72
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