Strain rate effect on the mechanical behaviour of a textile reinforced cement composite

The static tensile behaviour of Textile Reinforced Cement Composites is known and can be modeled adequately. However, using these static material properties under dynamic loadings such as impact and seismic loadings, can cause over- or underestimation of the material due to effects of strain rate. This work focuses on the strain rate dependency of a specific textile reinforced cement composite under tensile loadings at strain rates equivalent to quasi static applications towards low velocity impacts. It was found that the main damage mechanisms of this material stay the same. However cracking of the cement matrix is delayed to higher stress levels

Large-scale blast loading of a composite tube array for protection of civil engineering structures

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Experimental measurement of specific impulse distribution and transient deformation of plates subjected to near-field explosive blasts

The shock wave generated from a high explosive detonation can cause significant damage to any objects that it encounters, particularly those objects located close to the source of the explosion. Understanding blast wave development and accurately quantifying its effect on structural systems remains a considerable challenge to the scientific community. This paper presents a comprehensive experimental study into the loading acting on, and subsequent deformation of, targets subjected to near-field explosive detonations. Two experimental test series were conducted at the University of Sheffield (UoS), UK, and the University of Cape Town (UCT), South Africa, where blast load distributions using Hopkinson pressure bars and dynamic target deflections using digital image correlation were measured respectively. It is shown through conservation of momentum and Hopkinson-Cranz scaling that initial plate velocity profiles are directly proportional to the imparted impulse distribution, and that spatial variations in loading as a result of surface instabilities in the expanding detonation product cloud are significant enough to influence the transient displacement profile of a blast loaded plate

Multiscale modelling of the response of Ti-6AI-4V sheets under explosive loading

The objectives of the current study are to develop a multiscale numerical modelling method to predict the plastic deformation of Ti-6Al-4V sheets under blast loading, validate the method with experiments and characterise, at room temperature, the impulsive mechanical behaviour of the alloy. The numerical modelling technique relates the microstructure of the alloy with its macroscopic behaviour taking into account anisotropic effects by combining the viscoplastic self-consistent polycrystal model (VPSC7c) with the Cazacu-Barlat orthotropic yield criterion (CPB06) as implemented in the finite element (FE) solver of LS-DYNA. Sheet specimens of two thicknesses are tested using an experimental setup which applies a planar blast load. High speed cameras and the digital image correlation (DIC) technique are used to measure the evolving strains in the specimens. In addition, an analytical model is used to calculate the maximum displacements. The obtained values are compared with the outcome of the tests and FE simulations

Deformation measurements of blast loaded plates using digital image correlation and high-speed photography

This paper presents a study on the behaviour of aluminium plates subject to close range blast loads. Measurement of the full out-of-plane displacement field is performed combining two high-speed cameras in a stereoscopic set up and the digital image correlation technique. The measured displacement fields are compared to the calculated data using two different FEM codes. A good agreement has been found between both experimental and numerical data

Development of a numerical model for the ballistic penetration of Fackler gelatine by small calibre projectiles

Among the different material surrogates used to study the effect of small calibre projectiles on the human body, ballistic gelatine is one of the most commonly used because of its specific material properties. For many applications, numerical simulations of this material could give an important added value to understand the different phenomena observed during ballistic testing. However, the material response of gelatine is highly non-linear and complex. Recent developments in this field are available in the literature. Experimental and numerical data on the impact of rigid steel spheres in gelatine available in the literature were considered as a basis for the selection of the best model for further work. For this a comparison of two models for Fackler gelatine has been made. The selected model is afterwards exploited for a real threat consisting of two types of ammunitions: 9 mm and .44 Magnum calibre projectiles. A high-speed camera and a pressure sensor were used in order to measure the velocity decay of the projectiles and the pressure at a given location in the gelatine during penetration of the projectile. The observed instability of the 9 mm bullets was also studied. Four numerical models were developed and solved with LS-DYNA and compared with the experimental data. Good agreement was obtained between the models and the experiments validating the selected gelatine model for future use