JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 76

testing

Study of the bending stiffness of fibrereinforced thermoplastics at forming temperature
This paper presents different cantilever bending
tests used to characterize the bending stiffness
of fibre-reinforced thermoplastics at forming
temperature. The ASTM D1388 standard describes
a standard test method for determining the stiffness of fabrics (dry or impregnated) in a standard
atmosphere (21°C and 65% relative humidity).
This test was modified in this work for experimental studies above the melting temperature of
the polymer matrix.

By

Pr. Dr. bernD engeL, cHair of forMing tecHnoLogy
M. eng. JasMin graef, cHair of forMing tecHnoLogy
university of siegen

S

everal authors have described the influence of bending
stiffness on the formation of wrinkles. Thus, it is important to consider bending stiffness in finite element (FE)
forming analyses for better prediction of wrinkling.
Fibre-reinforced thermoplastics (FRTS) are gaining importance in the production of lightweight parts. After heating over
their melting temperature, they are formable several times and
can be processed using known stamping methods with suitable modifications. This makes it possible to use semi-finished
products in the form of pre-consolidated sheets. They do not
need a long curing time compared to reinforced thermosets.
Forming simulations of fibre-reinforced thermoplastics are
performed to understand and modify the forming process.
Simulation tools require the determination of specific material
parameters such as tensile, shear and bending stiffness at the
forming temperature of FRTS.
Shear stiffness is often identified by means of picture-frame
tests or bias-extension tests. However, there are no standardized

76 jec composites magazine / No103 March 2016

methods for the temperature-dependent characterization of
bending stiffness [1], but only a standard test method for the stiffness of fabrics (dry or impregnated) in a standard atmosphere
(21°C and 65% relative humidity) - ASTM D1388-96 [2].
The bending stiffness of FRTS at forming temperature is much
lower than their tensile stiffness in the fibre direction. Therefore, several authors who describe FE models for dry fabrics
assume that bending stiffness is negligible [3, 4].
[5-9] describe the influence of bending stiffness on the formation of wrinkles. Wrinkles occur due to the low bending and
shear stiffness of FRTS, whereas bending stiffness defines the
amount and size of the wrinkles [7].
Forming simulations are performed to predict the fibre orientation of reinforcements and wrinkling. Thus, it is important
to determine the shear, tensile and bending behaviour with
experimental tests for the validation of FE models.
In prior studies [1], several discrete approaches for the FE modelling of dry and impregnated fabrics as well as the fabric material model of Abaqus/Explicit were investigated and compared
for simulations of picture-frame shear test data.
There was a good agreement between discrete models and
experimental test results up to shear angles of about 40°. For
higher shear angles, there was a significant increase in the shear
stiffness of simulation results. The fabric material model has the
advantage that the shear and tensile response can be defined
based on test data [10], resulting in a better agreement with
experimental test data in the study. However, it just works for
membrane elements having no bending stiffness.
In further studies, beam elements or an offset of shell elements
according to Nishi et al. [11] will be added to the fabric model

Fig. 1: Cantilever bending test (fixed) (see [12, 13])



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #103 - March 2016

Cover
Edito
Point of view : Lamborghini
Contents
COMPANY & BUSINESS
In brief
Acquisition
Agenda of Events
APPLICATIONS
Sports & leisure
Sustainable construction
MARKET
Global
Europe
SPECIAL JEC WORLD 2016
Conferences
End-users
Automotive
Awards
Basalt
Engineering
Performing
Strategy
RESEARCH & DEVELOPMENT
Joining
Testing
Impact resistance
TECHNOLOGY & INNOVATIONS
Wind
Software
Epoxy
Repair
Thermoplastic
Sandwich
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Point of view : Lamborghini
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 8
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Ad2
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Ad3
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Ad4
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - In brief
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 11
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 12
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Acquisition
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 15
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Sports & leisure
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 18
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Sustainable construction
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Global
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 22
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 23
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Europe
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 26
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - SPECIAL JEC WORLD 2016
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Conferences
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 30
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 31
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 33
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 34
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 35
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 36
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 37
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - End-users
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Automotive
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 41
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Awards
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 44
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 46
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 48
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 50
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 52
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 53
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 55
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Basalt
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 58
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Engineering
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Performing
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 61
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 62
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 63
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Strategy
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 65
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 66
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 67
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 68
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 69
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - RESEARCH & DEVELOPMENT
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Joining
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 72
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 73
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 74
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 75
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Testing
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 77
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 78
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 79
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 80
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Impact resistance
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 82
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 83
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 84
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 85
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Wind
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 87
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Software
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 89
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 90
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Epoxy
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 92
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 93
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Repair
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 95
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Thermoplastic
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 97
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 98
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 99
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 100
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - Sandwich
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 102
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 103
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 104
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 105
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 107
JEC COMPOSITES MAGAZINE - Issue #103 - March 2016 - 108
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