Inelastic deformation micromechanism and modified fragmentation model for silicon carbide under dynamic compression

Abstract

The underlying micromechanism remains to be clarified for the bulk inelastic behaviour of specific ceramics under impact loads. In this study, the silicon carbide materials were subjected to the split-Hopkinson pressure bar compression in which the strain rate was not constant but increased to the dynamic level at high stresses. The inelastic deformation occurs in the high strain rate stage in compression, followed by the final transgranular fracture. The post-test fragments were examined in both the SEM and high resolution TEM. It was found that macroscopic inelastic behaviour is dominated by the dislocation motion and the localised amorphisation that arise at high strain rates. The damage and thus the degraded modulus in the dynamic inelastic deformation were incorporated to modify a dynamic fragmentation model to evaluate the fragment size as a function of strain rates. The modified model more accurately predicts the size of fragments produced at high strain rates.

Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

“…The uniaxial dynamic compression tests of the SPS-ed samples from Table 1 were conducted at the high strain rates of approximately 1000 s −1 in the SHPB system, which has been successfully used to characterize various other ceramics including silicon carbide 15 , alumina 16,17 , boron carbide 18,19 and MgB 2 20 . The end surfaces of the SPS-ed samples were polished, then examined by an optical microscope prior to mechanical testing; only the samples without surface defects were tested.…”

A model incorporating damage evolution to predict the penetration behavior of a ceramic target subjected to the long projectile impact

“…The previous experiments demonstrated that dynamic fragmentation of ceramic materials is sensitive to strain rates [6]. Higher strain rates lead to smaller fragment sizes.…”

“…As the key component in lightweight layered armour composites, ceramic materials provide the high resistance and energy dissipation capacity against penetrating impact. The ballistic performance of such armour ceramics has been studied experimentally and numerically under a range of small calibre ammunition impact [1][2][3][4][5][6]. The design and optimisation of the armour composite system require the accurate prediction of the penetration behaviour of ceramic materials subjected to high speed impact loading.…”

“…The constitutive model of the ceramic material was formulated by a linear elastic response [13] or a simplified yield surface [37]. However, the elastic modulus of brittle ceramic materials usually degrades with damage evolution at high strain rates [5,6]. It is thus necessary to incorporate such material degradation due to damage evolution into the material model to simulate the penetration process.…”