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5 Projectile Penetrations into Coarse Aggregated UHPCC Targets
while the contribution of fibers is very limited for the relatively low fiber addition ratio (≤3%); UHPCC with the compressive strength of 90 MPa and steel
fiber mixing ratio of 1.5% is the most optimum choice for protective structure
constructions.
(2) In Sect. 5.3, by conducting the projectile penetration test on UHP-CASFRC
and comparative HSC targets, it derives that, larger sized coarse aggregates
help to reduce the DOP, impact crater area and volume, and the harder coarse
aggregates decrease the DOP by aggravating the mass abrasions of the projectile. For the coarse aggregates with the size less than projectile shank, the harder
coarse aggregates only aggravate the mass abrasions of the projectile, and the
structural stability of the projectile could be maintained; For the structural
integrity of the projectile penetrating into UHP-CASFRC target, the structural
destruction of the penetrator (bend even fracture) occurs with enlarging the
corundum size. By comprehensively considering the anti-strike performance
and the workability of UHP-CASFRC, the corundum aggregate sizes ≥1.5d is
suggested for the constructions of protective structures.
(3) In Sect. 5.4, based on the 3D mesoscopic concrete model, the influence
of coarse aggregates strength (hardness) on the impact resistance of UHPC
targets is analyzed and discussed. The generation algorithms of 3D mesoscopic concrete model with randomly distributed sphere and convex polyhedron coarse aggregates are proposed. Regarding the 3D mesoscopic concrete
model meshed by hexahedral elements, the sphere and convex polyhedron
coarse aggregates have negligible differences for impact resistance of concrete
target; By simulating the experiments of projectile penetration into the CAUHPC targets, the 3D mesoscopic UHPC model with the randomly distributed
sphere coarse aggregates and corresponding constitutive parameters are validated; Based on the verified 3D mesoscopic UHPC model, the numerical
studies of projectile penetration into CA-UHPC, QA-UHPC, BA-UHPC and
LA-UHPC targets under different impact conditions are performed, respectively. According to the simulated results of DOP, residual velocity and ballistic
trajectory of projectile, it is found that the UHPC targets with high strength
(hardness) aggregates can increase the deflection, deformation and abrasion of
projectiles to improve the impact resistance of target. Furthermore, the relationship of impact resistance of four targets can be determined as: CA-UHPC
> QA-UHPC > BA-UHPC > LA-UHPC, and the impact resistance of CAUHPCC is much better than the others; for design concrete structures with
high protection standard, it is a good choice to adopt the CA-UHPC. In addition, under the premise of construction conditions, the particle size of corundum
aggregate is as large as possible, and it is best to be consistent with the diameter
of the projectile.
5 Projectile Penetrations into Coarse Aggregated UHPCC Targets
while the contribution of fibers is very limited for the relatively low fiber addition ratio (≤3%); UHPCC with the compressive strength of 90 MPa and steel
fiber mixing ratio of 1.5% is the most optimum choice for protective structure
constructions.
(2) In Sect. 5.3, by conducting the projectile penetration test on UHP-CASFRC
and comparative HSC targets, it derives that, larger sized coarse aggregates
help to reduce the DOP, impact crater area and volume, and the harder coarse
aggregates decrease the DOP by aggravating the mass abrasions of the projectile. For the coarse aggregates with the size less than projectile shank, the harder
coarse aggregates only aggravate the mass abrasions of the projectile, and the
structural stability of the projectile could be maintained; For the structural
integrity of the projectile penetrating into UHP-CASFRC target, the structural
destruction of the penetrator (bend even fracture) occurs with enlarging the
corundum size. By comprehensively considering the anti-strike performance
and the workability of UHP-CASFRC, the corundum aggregate sizes ≥1.5d is
suggested for the constructions of protective structures.
(3) In Sect. 5.4, based on the 3D mesoscopic concrete model, the influence
of coarse aggregates strength (hardness) on the impact resistance of UHPC
targets is analyzed and discussed. The generation algorithms of 3D mesoscopic concrete model with randomly distributed sphere and convex polyhedron coarse aggregates are proposed. Regarding the 3D mesoscopic concrete
model meshed by hexahedral elements, the sphere and convex polyhedron
coarse aggregates have negligible differences for impact resistance of concrete
target; By simulating the experiments of projectile penetration into the CAUHPC targets, the 3D mesoscopic UHPC model with the randomly distributed
sphere coarse aggregates and corresponding constitutive parameters are validated; Based on the verified 3D mesoscopic UHPC model, the numerical
studies of projectile penetration into CA-UHPC, QA-UHPC, BA-UHPC and
LA-UHPC targets under different impact conditions are performed, respectively. According to the simulated results of DOP, residual velocity and ballistic
trajectory of projectile, it is found that the UHPC targets with high strength
(hardness) aggregates can increase the deflection, deformation and abrasion of
projectiles to improve the impact resistance of target. Furthermore, the relationship of impact resistance of four targets can be determined as: CA-UHPC
> QA-UHPC > BA-UHPC > LA-UHPC, and the impact resistance of CAUHPCC is much better than the others; for design concrete structures with
high protection standard, it is a good choice to adopt the CA-UHPC. In addition, under the premise of construction conditions, the particle size of corundum
aggregate is as large as possible, and it is best to be consistent with the diameter
of the projectile.