JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 46

cure monitoring

Fig. 1: Multi-frequency cure data

Fig. 3: Multi-frequency data after electrode polarization correction

tionship between dielectric data and mechanical viscosity.
Ideally, ion viscosity is the frequency-independent (or DC)
resistivity ρ, which is the inverse of DC conductivity as defined
in equation 3. In many cases, this DC resistivity is proportional
to mechanical viscosity in the early portion of cure, and indicates the curing state in the latter portion of cure. Details of this
relationship are discussed in Lambient Technologies Application note 6: Dielectric measurements and viscosity.
Ion viscosity derived from data at a single frequency produces
a curve which characterizes the progress of cure. In simplified
form, Figure 4 shows the behaviour of a typical thermoset with
one ramp step and one hold step.
Fig. 2: Typical epoxy curing data, after electrode polarization correction

by a factor of 10.
For the early portion of cure in Figure 2, a factor of 10 separates
all loss factor curves, which therefore are inversely proportional
to frequency. At the end of cure, a factor of 10 only separates
loss factor curves for the lowest frequencies. DC conductivity
reflects the state of cure; therefore, choosing frequencies where
DC conductivity dominates is necessary for useful cure monitoring. The highest frequencies are best for observing events near
the beginning of cure, and the lowest frequencies for events
near the end of cure.
At the ideal end of cure, the crosslinking reaction stops and
change in the material ceases. This condition also means
that the ion mobility, and therefore the loss factor, becomes
constant with time.
Figure 3 shows data from multi-frequency curing after electrode
polarization correction. The distorted loss factor data has been
fixed and very closely resembles the curves of Figure 2. For
much of the cure, factors of 10 separate the loss factor curves,
which are inversely proportional to frequency and indicate the
dominance of DC conductivity.

Characteristics of thermoset curing
The term "ion viscosity" was coined to emphasize the rela-

The dielectric cure curve is characterized by four critical points:
- CP(1) - A user-defined level of ion viscosity that is typically
used to identify the onset of material flow at the beginning of
cure.
- CP(2) - Ion viscosity minimum, which typically also corresponds to the physical viscosity minimum. This critical point
indicates the time when the crosslinking reaction and resultant
increasing viscosity begin to dominate the decreasing viscosity
due to melting.
- CP(3) - Inflection point, which identifies the time when the
crosslinking reaction begins to slow. CP(3) is often used as a
signpost that can be associated with gelation.
- CP(4) - A user-defined slope that can define the end of cure.
The decreasing slope corresponds to the decreasing reaction
rate. Note that dielectric cure monitoring continues to reveal
changes in the evolving material past the point when mechanical measurement of viscosity is not possible.
During the initial ramp, ion viscosity decreases because the
thermoset is melting and becoming more fluid. At first, the
crosslinking reaction is slow, but the reaction rate increases as
the material becomes hotter. At minimum ion viscosity, which
also occurs at the time of minimum mechanical viscosity,
solidification due to crosslinking begins to dominate and ion
viscosity - and mechanical viscosity - begins to increase.
During the isothermal stage, ion viscosity increases continuously, and at some time the concentration of unreacted

46 jec composites magazine / No85 November - December 2013



JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013

Cover
Edito
Point of view: bespoke equipment
Contents
Agenda of Events
COMPANY & BUSINESS In Brief
APPLICATIONS
Large parts
Skateboard
Second life
Truck
Pipe
MARKET Process
FEATURE CONSTRUCTION
Roofing
PFRP house
Sandwich panels
GFRP grid
Gelcoat
Windows
Bridge
RESEARCH & DEVELOPMENT
Cure monitoring
Design
TECHNOLOGY & INNOVATIONS
NDC
Simulation
CBeam
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Cover
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 2
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Edito
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Point of view: bespoke equipment
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 5
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Contents
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 7
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 9
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - COMPANY & BUSINESS In Brief
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 11
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Large parts
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 13
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Skateboard
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 15
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Second life
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 17
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Truck
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 19
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Pipe
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 21
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 22
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - MARKET Process
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 24
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 25
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 26
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 27
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Roofing
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 29
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 30
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - PFRP house
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 32
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Sandwich panels
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 34
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 35
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - GFRP grid
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 37
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Gelcoat
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 39
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Windows
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 41
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Bridge
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 43
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 44
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Cure monitoring
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 46
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 47
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Design
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 49
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 50
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 51
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - NDC
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 53
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Simulation
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 55
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - CBeam
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - Index
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - In the world
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 59
JEC COMPOSITES MAGAZINE - Issue #85 - November/December 2013 - 60
https://www.nxtbook.fr/newpress/jeccomposites/jcm2211_148
https://www.nxtbook.fr/newpress/jeccomposites/jcm2209_147
https://www.nxtbook.fr/newpress/jeccomposites/jcm2206_146
https://www.nxtbook.fr/newpress/jeccomposites/jcm2204_145
https://www.nxtbook.fr/newpress/jeccomposites/jcm2201_144
https://www.nxtbook.fr/newpress/jeccomposites/jcm211_143
https://www.nxtbook.fr/newpress/jeccomposites/jcm2109_142
https://www.nxtbook.fr/newpress/jeccomposites/jcm2107_141
https://www.nxtbook.fr/newpress/jeccomposites/jcm2105_140
https://www.nxtbook.fr/newpress/jeccomposites/jcm2103_139
https://www.nxtbook.fr/newpress/jeccomposites/jcm-experts-digest-additive-manufacturing-2020
https://www.nxtbook.fr/newpress/jeccomposites/jcm2101_138
https://www.nxtbook.fr/newpress/jeccomposites/jcm2011_Special_Issue4
https://www.nxtbook.fr/newpress/jeccomposites/jcm2011_137
https://www.nxtbook.fr/newpress/jeccomposites/jcm2009_136
https://www.nxtbook.fr/newpress/jeccomposites/jcm2007_135
https://www.nxtbook.fr/newpress/jeccomposites/jcm_2020_Q1_Innovation_Report
https://www.nxtbook.fr/newpress/jeccomposites/jcm2005_Special_Issue3
https://www.nxtbook.fr/newpress/jeccomposites/jcm2005_134
https://www.nxtbook.fr/newpress/jeccomposites/jcm2003_133
https://www.nxtbook.fr/newpress/jeccomposites/jcm2001_132
https://www.nxtbook.fr/newpress/jeccomposites/jcm1911_Special_Issue2
https://www.nxtbook.fr/newpress/jeccomposites/jcm1911_131
https://www.nxtbook.fr/newpress/jeccomposites/jcm1909_130
https://www.nxtbook.fr/newpress/jeccomposites/jcm1907_129
https://www.nxtbook.fr/newpress/jeccomposites/jcm1905_128
https://www.nxtbook.fr/newpress/jeccomposites/jcm1903_Special_Issue1
https://www.nxtbook.fr/newpress/jeccomposites/jcm1903_127
https://www.nxtbook.fr/newpress/jeccomposites/jcm1901_126
https://www.nxtbook.fr/newpress/jeccomposites/jcm1811_125
https://www.nxtbook.fr/newpress/jeccomposites/jcm1810_124
https://www.nxtbook.fr/newpress/jeccomposites/jcm1808_123
https://www.nxtbook.fr/newpress/jeccomposites/jcm1807_122
https://www.nxtbook.fr/newpress/jeccomposites/jcm1805_121
https://www.nxtbook.fr/newpress/jeccomposites/jcm1804_120
https://www.nxtbook.fr/newpress/jeccomposites/jcm1803_119
https://www.nxtbook.fr/newpress/jeccomposites/jcm1802_119-Supplement_Innovation_Report
https://www.nxtbook.fr/newpress/jeccomposites/jcm1801_118
https://www.nxtbook.fr/newpress/jeccomposites/jcm1711_117
https://www.nxtbook.fr/newpress/jeccomposites/jcm1710_116
https://www.nxtbook.fr/newpress/jeccomposites/jcm1708_115
https://www.nxtbook.fr/newpress/jeccomposites/jcm1707_114
https://www.nxtbook.fr/newpress/jeccomposites/jcm1706_113
https://www.nxtbook.fr/newpress/jeccomposites/jcm1704_112
https://www.nxtbook.fr/newpress/jeccomposites/jcm1703_111
https://www.nxtbook.fr/newpress/jeccomposites/jcm1701_110
https://www.nxtbook.fr/newpress/jeccomposites/jcm1611_109
https://www.nxtbook.fr/newpress/jeccomposites/jcm1610_108
https://www.nxtbook.fr/newpress/jeccomposites/jcm1608_107
https://www.nxtbook.fr/newpress/jeccomposites/jcm1607_106
https://www.nxtbook.fr/newpress/jeccomposites/jcm1605_105
https://www.nxtbook.fr/newpress/jeccomposites/jcm1604_104
https://www.nxtbook.fr/newpress/jeccomposites/jcm1603_103
https://www.nxtbook.fr/newpress/jeccomposites/jcm1601_102
https://www.nxtbook.fr/newpress/jeccomposites/jcm1511_101
https://www.nxtbook.fr/newpress/jeccomposites/jcm1510_100
https://www.nxtbook.fr/newpress/jeccomposites/jcm1509_99
https://www.nxtbook.fr/newpress/jeccomposites/jcm1507_98
https://www.nxtbook.fr/newpress/jeccomposites/jcm1505_97
https://www.nxtbook.fr/newpress/jeccomposites/jcm1504_96
https://www.nxtbook.com/newpress/jeccomposites/jcm1503_95
https://www.nxtbook.com/newpress/jeccomposites/jcm1501_94
https://www.nxtbook.com/newpress/jeccomposites/jcm1412_93
https://www.nxtbook.com/newpress/jeccomposites/jcm1410_92
https://www.nxtbook.com/newpress/jeccomposites/jcm1409_91
https://www.nxtbook.com/newpress/jeccomposites/jcm1406_90
https://www.nxtbook.com/newpress/jeccomposites/jcm1405_89
https://www.nxtbook.com/newpress/jeccomposites/jcm1404_88
https://www.nxtbook.com/newpress/jeccomposites/jcm1403_87
https://www.nxtbook.com/newpress/jeccomposites/jcm1401_86
https://www.nxtbook.com/newpress/jeccomposites/jcm1311_85
https://www.nxtbook.com/newpress/jeccomposites/jcm1310_84
https://www.nxtbook.com/newpress/jeccomposites/jcm1308_83
https://www.nxtbook.com/newpress/jeccomposites/jcm1307_82
https://www.nxtbook.com/newpress/jeccomposites/jcm1305_81
https://www.nxtbook.com/newpress/jeccomposites/jcm1304_80
https://www.nxtbook.com/newpress/jeccomposites/jcm1303_79
https://www.nxtbook.com/newpress/jeccomposites/jcm1301_78
https://www.nxtbook.com/newpress/jeccomposites/jcm1212_77
https://www.nxtbook.com/newpress/jeccomposites/jcm1210_76
https://www.nxtbook.com/newpress/jeccomposites/jcm1208_75
https://www.nxtbook.com/newpress/jeccomposites/jcm1207_74
https://www.nxtbook.com/newpress/jeccomposites/jcm1206_73
https://www.nxtbook.com/newpress/jeccomposites/jcm1204_72
https://www.nxtbook.com/newpress/jeccomposites/jcm1203_71
https://www.nxtbook.com/newpress/jeccomposites/jcm1201_70
https://www.nxtbook.com/newpress/jeccomposites/jcm1111_69
https://www.nxtbook.com/newpress/jeccomposites/jcm1110_68
https://www.nxtbook.com/newpress/jeccomposites/jcm1108_67
https://www.nxtbook.com/newpress/jeccomposites/jcm1107_66
https://www.nxtbook.com/newpress/jeccomposites/jcm1105_65
https://www.nxtbook.com/newpress/jeccomposites/jcm1104_64
https://www.nxtbook.com/newpress/jeccomposites/jcm1103_63
https://www.nxtbook.com/newpress/jeccomposites/jcm1101_62
https://www.nxtbook.com/newpress/jeccomposites/jcm1011_61
https://www.nxtbook.com/newpress/jeccomposites/jcm1010_60
https://www.nxtbook.com/newpress/jeccomposites/jcm1009_59
https://www.nxtbook.com/newpress/jeccomposites/jcm1006_58
https://www.nxtbook.com/newpress/jeccomposites/jcm1005_57
https://www.nxtbook.com/newpress/jeccomposites/jcm1004_56
https://www.nxtbook.com/newpress/jeccomposites/jcm1003_55
https://www.nxtbook.com/newpress/jeccomposites/jcm1001_54
https://www.nxtbook.com/newpress/jeccomposites/jcm0911_53
https://www.nxtbook.com/newpress/jeccomposites/jcm0910_52
https://www.nxtbook.com/newpress/jeccomposites/jcm0909_51
https://www.nxtbook.com/newpress/jeccomposites/jcm0907-08_50
https://www.nxtbook.com/newpress/jeccomposites/jcm0906_49
https://www.nxtbook.com/newpress/jeccomposites/jcm0904_48
https://www.nxtbook.com/newpress/jeccomposites/jcm0903_47
https://www.nxtbook.com/newpress/jeccomposites/jcm0901_46
https://www.nxtbook.com/newpress/jeccomposites/jcm0811_45
https://www.nxtbook.com/newpress/jeccomposites/jcm0810_44
https://www.nxtbook.com/newpress/jeccomposites/jcm0809_43
https://www.nxtbook.com/newpress/jeccomposites/jcm0807_42
https://www.nxtbook.com/newpress/jeccomposites/jcm0806_41
https://www.nxtbook.com/newpress/jeccomposites/jcm0805_40
https://www.nxtbook.com/newpress/jeccomposites/jcm0803_39
https://www.nxtbook.com/newpress/jeccomposites/jcm0801_38
https://www.nxtbook.com/newpress/jeccomposites/jcm0712_37
https://www.nxtbook.com/newpress/jeccomposites/jcm0710_36
https://www.nxtbook.com/newpress/jeccomposites/jcm0709_35
https://www.nxtbook.com/newpress/jeccomposites/jcm0707_34
https://www.nxtbook.com/newpress/jeccomposites/jcm0706_33
https://www.nxtbookmedia.com