JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014 - 43

as UP resin or UP/phenolic blends with 1% MEKP catalyst
content by weight, is shown in Figure 2b. In this case, there
is no indication of curing mechanism, but the thermocouples are able to sense the flow (with obvious changes)
due to the heat capacity difference between the fibres and
the resin. This flow front sensing method was tried using a
variety of resins and non-toxic liquids (e.g. corn oil, corn
syrup), and the results were repeatable with the current
experimental setup.

Fig. 4: 3D resin flow front advancement

Due to the high sensitivity of the Compact-Rio kit
(38µV/0.02°C), the thermocouples compacted and sealed
between the fabric layers in the stack are able to acquire
very small temperature changes. The thermocouples exhibit different responses for slow and medium/fast curing
resins. The flow front data detection for a resin system with
a medium/fast curing mechanism, such as Prime 20LV
epoxy resin with 26% hardener content by weight, is shown
in Figure 2a. In this case, once the resin system arrives at a
thermocouple location there is a clear temperature rise due
to the ongoing curing reactions. The flow front data detection for a resin system with a slow curing mechanism, such

A 3D resin flow example without an infusion mesh (using
a glass mould, thermocouples and one camera located on
each side) for a 12-layer non-crimp glass fibre preform
(length 45 cm, width 15 cm) incorporating thermocouples
located on one side of the preform between different layers
(seven thermocouples between 4th and 5th, and seven
thermocouples between 8th and 9th) can be seen in Figure
3. In this case, the through-thickness flow data detected by
the cameras and the thermocouples are presented in Figure
4.
An example of cure monitoring results (using two FBGs
and a thermocouple) for a UP/phenolic sample during and
after infusion, under the vacuum pressure of 100 millibar,
is shown in Figure 5. FBG-2 is sealed by a capillary tube to
detect temperature changes only. This data helps to cancel
out the temperature effect to measure the actual strain
development and the residual stain values.

Resin characterisation

a) VI process

The industrial project partners Scott Bader and Sumitomo-Bakelite Europe are collaborating with Southampton
University to supply and characterise the resins. The
resin systems are UP resin (Crystic 702 with MEKP
catalyst from Scott Bader) and three types of phenolics
(Durez-33166, Plyophen-23983 and Methylon-75108 from
Sumitomo Bakelite). Three different blends are investigated by blending the UP resin with each phenolic. According
to the differential scanning calorimetry (DSC) analyses,
the blends resulted in very complex cure cycles (Table 1).
More details of the UP/phenolic blends used in the global
project can be found in the study conducted by Deli [2].
The cure cycles of the blends for different mixing ratios are
still under investigation by Bolton University for more simplification. The infusions take place at room temperature,
Tab. 1: Cure cycles for 50:50 blends

Type
UP/Plyophen

b) Cure
Fig. 5: VI process and cure monitoring results for a UP/phenolic sample

Cure cycles
6hr-50°C/8hr-80°C/8hr-100°C/2hr-130°C

UP/Durez

24hr-70°C/1hr-100°C/1hr-130°C /1hr-160°C

UP/Methylon

6hr-50°C/12hr-80°C/8hr-100°C/6hr-120°C/6hr130°C/2hr-150°C/2hr-170°C

No90 June - July 2014 /

jec composites magazine 43

JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014