SAMPE Journal - July/August 2016 - 52

Feature Article
Table 1. Test methods and panel configurations.

CFRP's Properties
The prepregs were cut and hand-laid up for
autoclave, VBO, and Quickstep molding processes.
Table 1 summarizes the mechanical evaluation of
interest.
For autoclave curing, the non-interlayer
toughened system and the interlayer toughened
system were cured at 135°C for 2 hr and 180°C
for 2 hr, respectively. In both cases, a ramp rate of
about 2°C/min and an autoclave pressure of 0.59
MPa were applied.
For VBO curing, the non-interlayer toughened
system was dwelled at 88°C for 1.5 hr and cured
at 132°C for 2 hr. The interlayer toughened system
was dwelled at 120°C for 1.5 hr and cured at 180°C
for 2 hr. In both cases, a ramp rate of about 2°C/
min, a PVT of 3 hr, and a vacuum pressure of 0.10
MPa were applied.
For Quickstep curing, conditions from VBO were
initially used and further optimized for each prepreg
to achieve a lower cycle time and void contents as
possible. In both cases, a ramp rate between 2030°C/min, a PVT of less than 0.5 hr, and a total of
0.14 MPa compaction pressure were targeted.
Analysis
A dynamic viscoelasticity measuring device
(ARES, manufactured by TA Instruments) was used
to obtain resin viscosity profiles vs. temperature.
52

Parallel plates were used. Ramp rates were 2-10°C/
min. A strain of 10%, a frequency of 0.5 Hz, and a
gap between two plates of 1 mm were applied.
A Differential Scanning Calorimeter (DSC) TA
Instruments Q200 was used to obtain heat flow as a
function of temperature. Ramp rates were 2-10°C/
min. Glass transition temperature and degree of
cure was also identified. The degree of cure is
determined by comparing the exothermic reaction
peak area of an uncured resin against that of the
corresponding cured resin to obtain a percentage.
A Mistras UPK-T36C pulse echo ultrasonic
scanner was used to document anomalies prior
to preparation of cross sectioned samples for
microscopy. A 3.5 MHz frequency transducer with
3.8 cm focal length was used. Step resolution set
at 0.001 cm and a scanning resolution of 0.13 cm.
A Nikon LABOPHOT-2 optical microscope was
used to document the interlayer thickness and void
content. The samples were prepared by mechanical
polishing 90° cross-sections of the CFRP laminate
in various locations.
Results and Discussion
Fast Ramp Characteristics
Typical curing ramp rates for composites revolve
around 2°C/min as seen in VBO and an autoclave.
For aerospace grade prepregs, a cure time around
6 hr is typical for VBO and 4-6 hr for autoclave. In
SAMPE Journal, Volume 52, No. 4, July/August 2016



Table of Contents for the Digital Edition of SAMPE Journal - July/August 2016

Contents
SAMPE Journal - July/August 2016 - Cover1
SAMPE Journal - July/August 2016 - Cover2
SAMPE Journal - July/August 2016 - Contents
SAMPE Journal - July/August 2016 - 2
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