Composite Materials Research Progress

Damage Variables in Impact Testing of Composite Laminates 247
Interestingly, up to Pn the DI increases linearly with the impact energy to then grow quite
abruptly over the range of the penetration process. A linear relationship also exists between
the DD data and the impact energy; however, the DD data can not be used beyond penetration
as (by definition) the DD stays at the value of one over the entire range of the penetration
process.
DI
DD, DI
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
GVP90_12.31 GE90s_8.00
GE90m_8.00 GE45_4.50
GE90s_4.00 GE90m_4.00
CE60_1.75 CE90_1.55
CE60_0.85 CE90_0.75
CE60_0.40 CE90_0.35
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
E i/P n
Figure 6. DI values plotted against non-dimensional impact energy E i/P n
y = 0.68x + 0.28
R 2 = 0.96
y = 0.52x - 0.14
R 2 = 0.99
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
E i/P n
DD DI
Figure 7. Comparison between DD and DI values for impact tests on glass/epoxy 6.25 mm thick
laminates. Impact data taken from reference [17].