6.4 Discussions
183
superscript * is added to distinguish the data of no aggregated UHP-SFRC in the
2nd row. It should be noted that, two assumptions were adopted during the above
calculations: (i) the enhancing degree of adding coarse aggregates given by Eq. (6.5)
for NSC was also suitable for UHP-SFRC; (ii) the enhancing degree of adding coarse
aggregates on DOP was identical to the one on perforation limit.
Besides, aiming to further validate the distinguished impact resistance of the
present optimal UHP-BASFRC, another impact scenario was assumed in the last row
of Table 6.4, in which the UHP-SFRC (151.7 MPa) panels without coarse aggregate
in Máca et al. (2014) was struck by the 7.62 mm API bullet used in the present test.
From Tables 6.3 and 6.4, it is derived that:
(1) As for no coarse aggregated UHP-SFRC in Sovják et al. (2015) and Máca et al.
(2014), Chen’s model (Chen et al. 2008) shows high degree of accuracy with
the test data; Wu’s model (Wu et al. 2015a) gives over predictions, and the
reason lies in that Eq. (6.4) was obtained by fitting the ogive-nosed projectile
perforation tests data and overestimate the perforation capacity of the truncatedogive-nosed projectile; the modified NDRC (Li et al. 2005) and Kar (1978)
formulae both show poor prediction accuracies.
(2) As for UHP-BASFRC, the existing four models all give poor predictions. When
the decreasing effect on perforation limit of the coarse aggregate was considered, Chen’s model (Chen et al. 2008) also shows good predictions (the 3rd
row in Table 6.4). Thus, Chen’s model (Chen et al. 2008) given in Eq. (6.3)
with a reduction coefficient of 77.7% can be used as a practical approach to
predict the terminal ballistic parameters of bullet impacting on UHP-BASFRC
targets. However, the validation of above approach should be further verified
by more tests.
(3) In the last row of Table 6.4, the predicted perforation limit 90.41 mm was
obtained from Chen’s model (Chen et al. 2008), and it was considered correct
based on the above discussions. By comparing the predicted results in rows
2 and 4, for the same bullet and strike velocity, the perforation limit of the
present UHP-BASFRC (77.2 mm) panel is nearly 14.6% lower than that of the
UHP-SFRC (90.41 mm) panel even though the former compressive strength
(106.2 MPa) is only 70% of the latter (151.7 MPa). The excellent impact
resistance of the designed UHP-BASFRC was validated.
6.4.3 Fabric Effect
Comparisons among the damage of targets in Shots 1-8, 2-7, 2-8, 3-7 and 38 show that the perforation limits of the UHP-BASFRC/UHMWPE and UHPBASFRC/CFRP panel located within the range of 68.7–77.2 mm and 67.2–77.2 mm,
respectively. It can be derived that rear fabrics help to decrease the perforation limit
of the UHP-BASFRC panels impacted by the small caliber arms, and the maximal
reducing magnitudes are (77.2 − 68.7)/77.2 = 11% and (77.2 − 67.2)/77.2 = 13%
for UHMWPE and CFRP, respectively. Almusallam et al. (2015) obtained that the
183
superscript * is added to distinguish the data of no aggregated UHP-SFRC in the
2nd row. It should be noted that, two assumptions were adopted during the above
calculations: (i) the enhancing degree of adding coarse aggregates given by Eq. (6.5)
for NSC was also suitable for UHP-SFRC; (ii) the enhancing degree of adding coarse
aggregates on DOP was identical to the one on perforation limit.
Besides, aiming to further validate the distinguished impact resistance of the
present optimal UHP-BASFRC, another impact scenario was assumed in the last row
of Table 6.4, in which the UHP-SFRC (151.7 MPa) panels without coarse aggregate
in Máca et al. (2014) was struck by the 7.62 mm API bullet used in the present test.
From Tables 6.3 and 6.4, it is derived that:
(1) As for no coarse aggregated UHP-SFRC in Sovják et al. (2015) and Máca et al.
(2014), Chen’s model (Chen et al. 2008) shows high degree of accuracy with
the test data; Wu’s model (Wu et al. 2015a) gives over predictions, and the
reason lies in that Eq. (6.4) was obtained by fitting the ogive-nosed projectile
perforation tests data and overestimate the perforation capacity of the truncatedogive-nosed projectile; the modified NDRC (Li et al. 2005) and Kar (1978)
formulae both show poor prediction accuracies.
(2) As for UHP-BASFRC, the existing four models all give poor predictions. When
the decreasing effect on perforation limit of the coarse aggregate was considered, Chen’s model (Chen et al. 2008) also shows good predictions (the 3rd
row in Table 6.4). Thus, Chen’s model (Chen et al. 2008) given in Eq. (6.3)
with a reduction coefficient of 77.7% can be used as a practical approach to
predict the terminal ballistic parameters of bullet impacting on UHP-BASFRC
targets. However, the validation of above approach should be further verified
by more tests.
(3) In the last row of Table 6.4, the predicted perforation limit 90.41 mm was
obtained from Chen’s model (Chen et al. 2008), and it was considered correct
based on the above discussions. By comparing the predicted results in rows
2 and 4, for the same bullet and strike velocity, the perforation limit of the
present UHP-BASFRC (77.2 mm) panel is nearly 14.6% lower than that of the
UHP-SFRC (90.41 mm) panel even though the former compressive strength
(106.2 MPa) is only 70% of the latter (151.7 MPa). The excellent impact
resistance of the designed UHP-BASFRC was validated.
6.4.3 Fabric Effect
Comparisons among the damage of targets in Shots 1-8, 2-7, 2-8, 3-7 and 38 show that the perforation limits of the UHP-BASFRC/UHMWPE and UHPBASFRC/CFRP panel located within the range of 68.7–77.2 mm and 67.2–77.2 mm,
respectively. It can be derived that rear fabrics help to decrease the perforation limit
of the UHP-BASFRC panels impacted by the small caliber arms, and the maximal
reducing magnitudes are (77.2 − 68.7)/77.2 = 11% and (77.2 − 67.2)/77.2 = 13%
for UHMWPE and CFRP, respectively. Almusallam et al. (2015) obtained that the