10
 -B-Exper. (Aver. of 3)
 8 -X-Model




 4

 2

 0
 0 0.002 0.004 0.006 0.008 0.01
 Strain (in/in)


Figure 8-15. Stress-strain curves for grid diameter of 5.5 in.

 The effect of additional layers of grid on the strength and ductility of the cylinder

was determined by simply increasing the number of CFRP grid layers. This was done for

2, 4, 5 and 6 layers for cylinders with a grid diameter of 5.5 in. (see Fig. 8-16).

 10

 8



 4
 -X- M, H & A (2 layers)
 M, H & A (4 layers)
 2 -- M, H & A (5 layers)
 -A- M, H & A (6 layers)

 0 0.003 0.006 0.009 0.012 0.015
 Strain (in/in)


Figure 8-16. Stress-strain curves for different amounts of CFRP grid

 The addition of the extra CFRP layers had a significant effect on their ductility with

the cylinders with the higher number of grid layers having higher ultimate strains. The

effect of the CFRP grid on the strength of the cylinder was small (10% increase for the 2

layers and 16% increase for the 6 layers compared to the unconfined strength). The

increase in the ultimate strain was very significant and was increasing as the amount of