A hyper-viscoelastic constitutive model for polyurea by separating hyperelastic and viscoelastic behaviors has been put forward. Hyperelasticity represents the rate-independent responses at low strain rates, described by a three-parameter Mooney-Rivlin model and a third Ogden model. By fitting the quasi-static experimental data, the Ogden model is more appropriate to describe the hyperelastic behaviors for its better agreement at strain over 0.3. Meanwhile, viscoelasticity represents the rate-dependent responses at high strain rates, described by the Standard Linear Solids (SLS) model and the K-BKZ model. By fitting the experimental data of split Hopkinson pressure bar (SHPB), the SLS model is more appropriate to describe the viscoelastic behaviors at strain rates below 1600 s⁻¹, but the K-BKZ model performs better at strain rates over 2100 s⁻¹ because of the substantial increase of Young’s modulus and the state of polyurea transforming from rubbery to glassy. The K-BKZ model is chosen to describe the viscoelastic behavior, for its low Root Mean Square Error (RMSE) at strain rates below 1600 s⁻¹. From the discussion above, the hyper-viscoelastic constitutive model is chosen to be the combination of the Ogden model and the K-BKZ model.

In this paper, a novel linear shaped charge (LSC), called a bi-apex-angle linear shaped charge (BLSC), has been designed to investigate the improvement of penetration performance. Compared with a traditional single-apex-angle LSC, a BLSC, which consists of a small-apex-angle liner and a large-apex-angle liner, has been investigated by depth-of-penetration (DOP) test. The results show that the penetration depth of BLSC is 29.72% better than that of an ordinary LSC. An Eulerian method is applied to simulate the entire process of jet formation, as well as penetration on a #45 steel target. The effectiveness of the Eulerian model is demonstrated by the good agreement of the computational results with experimental observations. Furthermore, the numerical simulation is developed to investigate the influence of liner thickness, explosive type, combination of small and large apex angle, ratio of small to all apex angle liner, and standoff distance on the penetration performance of BLSCs. The suggested work and results can provide a guide and reference for the structural design of BLSC.

This paper presents the results of an experimental and numerical study conducted to investigate the mechanism of penetration of linear shaped charges (LSCs) into double layered targets. A type of LSC causing less collateral damage in terms of jet residues was studied. The LSC consisted of a linear liner and case with the depth to diameter aspect ratio of 2.0. Anti-theft doors and spaced steel plates were used to represent double layered targets. The anti-theft door and the equivalent targets were penetrated with little jet residues behind the exit crater. The experiments were simulated using the commercially available software AutoDYN as a 2-D planer symmetry FEM model of the LSC penetrating a double layered target. An Eulerian mesh was used to model the LSCs whilst the double layered target was modelled using a Lagrangian mesh. A fully coupled algorithm was used for two different meshes. The data from the experiments (the shape of the breach and jet residues) were used to validate the numerical model. The validated numerical model was used to gain insights into the penetrating mechanisms of the LSC. The numerical results indicated that the penetration mechanisms of the two layers target were different. The first layer was penetrated by a continuous jet typical of a high-speed jet whereas the second layer was perforated by both a jet tip and slug characterized by a low-impact velocity projectile (slug).