Table 3-2. Results for CFRP grid specimens
Specimen Grid roll Area Peak Strength Modulus
 direction (in2) load (ksi) (ksi)
 (lbf)
 T1 Transverse 0.0123 841.5 68.5 7433
 T2 Transverse 0.0091 1147.5 126.2 8514
 L1 Longitudinal 0.0094 924.8 98.0 9486
 L2 Longitudinal 0.0080 891.0 110.8 11508

 120

 100- Ol T1 AT2 oL1 XL2
 .,- 80-----y=11516x
 0 80
 y80 = 9671.2x
 60y = 8548.9x
 S60
 y = 7665.4x
 40

 20


 0 0.003 0.006 0.009 0.012
 Strain (in/in)

Figure 3-5. Stress-strain curves of CFRP grid strands

 Although insufficient tests were conducted to reveal statistical significance, some

indication of strength consistency can be determined from the test data. The coefficient

of variance (COV) for the strength was 24.2% while for the tensile modulus 17.4%. Both

COVs were high and were attributed to the variability between the CFRP strands. Some

strands had a thick layer of epoxy resin covering them, which resulted in a lower fiber

volume fraction. According to the manufacturing company (TechFab 2004) strands in

both the longitudinal and transverse direction have the same capacity. Tests conducted

here indicated 9% higher capacity for the longitudinal strands compared to the transverse

strands but that was attributed to the high variability and the small number of specimens

in each direction.