Sphere and Bullet Impact Cone Crack Correlation in Armour Ceramics
M.G.L. Mourmans (TU Delft - Aerospace Engineering)
Y. Tang – Mentor (TU Delft - Group Tang)
Prakhar Jindal – Mentor (TU Delft - Space Systems Egineering)
E.P. Carton – Mentor (TNO)
S.R. Turteltaub – Graduation committee member (TU Delft - Group Turteltaub)
S. Giovani Pereira Castro – Mentor (TU Delft - Group Giovani Pereira Castro)
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Abstract
Cone crack formation is the primary damage evolution in brittle ceramics subjected to ballistic impact. This work investigates the correlations between cone cracks generated by low velocity sphere impact and those formed under high velocity bullet impact. alumina, silicon carbide, and silicon nitride ceramic tiles of varying thickness were experimentally tested for three velocity regimes (≤250 m/s, 300–550 m/s, ≥600 m/s). Macrostructural cone geometry was characterized using 3D optical microscopy and high speed imaging, mesostructural topology was evaluated through incremental mean arithmetic roughness measurements along the crack propagation, and microscopic fracture modes were quantified via SEM-based areal occurrence analysis.
Primary cone angles exhibit discrete regime-dependent plateaus achieved at transition velocities rather than continuous velocity dependence. Statistically significant inverse linear relationships are identified between primary cone angle and tile thickness, and between secondary cone angle and secondary cone height. Cone nucleation depth and minor cone radius scale proportionally with projectile radius, independent of ceramic material and velocity regime, indicating projectile-controlled nucleation geometry. Surface roughness increases progressively along the crack path for all materials and projectiles, suggesting propagation induced development of topological features. In contrast, material dependent distinct fracture modes are identified with minimal effects from projectile geometry and velocity.
Comparison between sphere and ballistic impacts reveals overlapping primary cone angle regimes, similar surface roughness amplifications, and comparable fracture modes, indicating similar crack nucleation and propagation mechanics at similar projectile velocities. Differences are primarily expressed in magnitudes of cone fragmentation and specimen recoverability for postmortem characterization of bare ceramic tiles.
In general, geometry is dominant for determining cone crack morphology, and intrinsic material properties govern microstructural fracture modes. Sphere impact testing can serve as a representative predictive screening method for understanding ballistic cone crack behaviour within defined regimes.