2894
2895
2896
4891
Resin KIC (MPa·m )
1.74
2.07
1.86
1.41
Minimum Viscosity (mPa·s)
35
53
62
75
Resin Tensile Modulus (GPa)
3.2
2.8
2.7
4.1
Tensile Strain at Failure (%)
7.7
9.0
7.0
4.4
Ultimate Tensile Stress (MPa)
96
82
84
101
Tg by E' Onset (°C)
155
166
179
186
Tg by tan d Peak (°C)
166
177
189
197
1/2
Table 2. Neat resin properties.
appropriate standards and conditioned according
to ASTM D5229 Procedure 'D' for dried specimens
and Procedure 'BHEE' for wet specimens. "Dry"
specimens were conditioned at 70°C and "Hot/
Wet" specimens were conditioned at 85°C/85% relative humidity.
The ultimate compressive strength of the
composite Panel B specimens was determined
according to ASTM D6641/D6641M (Combined
Loaded Compression - "CLC"). Untabbed specimens were utilized according to Procedure A of the
standard. The ultimate interlaminar shear strength
(short beam shear - "SBS") of Panel B specimens
was determined according to ASTM D2344/
D2344M. The ultimate open hole compression
strength ("OHC") of the Panel C specimens was
determined according to ASTM D6484/D6484M,
Procedure B.
For elevated temperature measurements, the
test temperature was recorded using a calibrated
digital thermometer with a 'K' thermocouple affixed
to the test fixture near the specimen gage area.
The mode I fracture behavior ("GIC") was determined for unconditioned Panel B specimens
according to ASTM D5528. Values reported were
calculated using the compliance calibration method for propagation. The mode II fracture behavior
("GIIC") was determined for unconditioned Panel B
specimens according to a 3M internal procedure
based on ASTM D7905.
Values reported were calculated using the fivepoint compliance calibration method. Specimens
were tested at a rate of 2 mm/min initially followed
by 5 mm/min to final break.
Compression after impact ("CAI") was measured according to ASTM D7136/7137. Panel A
specimens were impacted with a standard impactor with a target energy of 35 J. The compression
strength after impact was measured according to
ASTM D7137 with four strain gauges affixed to the
specimens to ensure even application of the compressive load. All specimens exhibited a lateral failure through the middle of the damage area.
w w w. s a m p e . o r g
Figure 1. Glass transition temperature of neat resin castings by differential
mechanical analysis.
RESULTS
As described in the introduction, 3M™ Matrix
Resin 2894 is an example of the class of RTM epoxy resin systems with high impact resistance and
modest service temperature and serves as a baseline for this study. Resin 2894 has a very respectable
KIC fracture toughness of 1.74 MPa·m1/2 and tensile
strength of 96 MPa and 7.7% strain to failure as is
shown in Table 2. In this study, two additional resin systems, Resins 2895 and 2896 have been studied with somewhat higher fracture toughness and
tensile properties, and with sequentially increasing
glass transition temperatures of 177°C/166°C (tan
d peak/E' inflection) for 2895 and 189°C/179°C for
2896 as shown in Table 2 and Figure 1. Matrix Resins
2895 and 2896 have somewhat higher KIC values of
2.07 and 1.86 MPa·m1/2 respectively. The neat resin tensile strengths are somewhat lower than 2894
at 82 and 84 MPa respectively. The modest service
temperature of 2894 is partially the result of the
lower glass transition temperature of 166°C/155°C.
Resin 2894 shows higher composite compres-
J U LY/AU G U S T 2 0 2 0
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SAMPE JOURNAL
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