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Abstract The coal mining process is affected by various water sources such as groundwater and coal seam water injection. Understanding the dynamic mechanical parameters of water-immersed coal is helpful for coalmine safe production. The impact compression tests were performed on coal with different moisture contents by using the ϕ50 mm Split Hopkinson Pressure Bar (SHPB) experimental system, and the dynamic characteristics and energy loss laws of water-immersed coal with different compositions and water contents were analyzed. Through analysis and discussion, it is found that: (1) When the moisture content of the coal sample is 0%, 30%, 60%, the stress, strain rate and energy first increase and then decrease with time. (2) When the moisture content of the coal sample increases from 30% to 60%, the stress “plateau” of the coal sample becomes more obvious, resulting in an increase in the compressive stress stage and a decrease in the expansion stress stage. (3) The increase of moisture content of the coal sample will affect its impact deformation and failure mode. When the moisture content is 60%, the incident rod end and the transmission rod end of the coal sample will have obvious compression failure, and the middle part of the coal sample will also experience expansion and deformation. (4) The coal composition ratio suitable for the coal immersion softening impact experiment is optimized.

The coal mining process is affected by various water sources such as groundwater and coal seam water injection. Understanding the dynamic mechanical parameters of water-immersed coal is helpful for coalmine safe production. The impact compression tests were performed on coal with different moisture contents by using the ϕ50 mm Split Hopkinson Pressure Bar (SHPB) experimental system, and the dynamic characteristics and energy loss laws of water-immersed coal with different compositions and water contents were analyzed. Through analysis and discussion, it is found that: (1) When the moisture content of the coal sample is 0%, 30%, 60%, the stress, strain rate and energy first increase and then decrease with time. (2) When the moisture content of the coal sample increases from 30% to 60%, the stress “plateau” of the coal sample becomes more obvious, resulting in an increase in the compressive stress stage and a decrease in the expansion stress stage. (3) The increase of moisture content of the coal sample will affect its impact deformation and failure mode. When the moisture content is 60%, the incident rod end and the transmission rod end of the coal sample will have obvious compression failure, and the middle part of the coal sample will also experience expansion and deformation. (4) The coal composition ratio suitable for the coal immersion softening impact experiment is optimized. [ABSTRACT FROM AUTHOR]

Whereas most previous studies have focused on improving the penetration resistance of Shear Thickening Fluids (STFs) treated composites, in this study, the dynamic compressive response of single and multi-ply 3 D E-Glass Fiber Reinforced Polymer (GFRP) composites with the STF matrix was investigated by using a drop-weight low-velocity impact test. The experimental results revealed the STF improved the compressive and cushioning performance of the composites such that with increasing its concentration, further improvement was observed. The five-ply composite containing the STF of 30 wt% silica nanoparticles and 1 wt% carbon nanotubes (CNTs) reduced the applied peak force by 56% and 26% compared to a steel plate and five-ply neat samples, respectively. A series of repeated impacts was performed, and it was found that the performance of high-concentration composites is further decreased under this type of loading. [ABSTRACT FROM AUTHOR]

Self-compacting rubberized concrete (SCRC), as the primary material of road construction, is produced by adding rubber particles instead of sand to self-compacting concrete (SCC). Four kinds of concrete with different rubber contents (0%, 5%, 10%, and 15%) are tested in this study. The materials testing systems (MTS) and split Hopkinson pressure bar (SHPB) are employed to obtain quasi-static mechanical properties (compressive, splitting tensile, and bending) and dynamic mechanical properties at high strain rates (100–250 s−1). The results reveal that quasi-static mechanical strength decreases with the increase in rubber content. Compared with SCC, SCRC is dramatically high in ductility. With the increase of the strain rate, the dynamic compressive strength, peak toughness, specific energy absorption (SEA), and dynamic increase factors (DIF) all rise. The dynamic compressive strength decreases with the ascending of rubber content, while the toughness index, peak toughness, and SEA increase with the increasing rubber content. Exponential and linear fittings are utilized to help further understand the influence of strain rates. The craze-shear band-cavitation theory can also help well explain the transition strain rate of peak toughness curves. The failure modes under high strain rates are observed. The results reveal that SCRC exhibits a stronger sensitivity to rubber content and has better impact toughness than SCC. [ABSTRACT FROM AUTHOR]

Abstract Compressive mechanical response of a developed polymer composite material over a wide strain rate range of 0.0001/s-8000/s is investigated. The developed polymer composite material shows the following stress-strain relation under high rate compressive loading: linear elasticity to a high yield stress, softening behavior with a slight stress decrease, plateau stress accompanied by a large plasticity and densification with a stress increase. Rate dependency of mechanical properties is revealed quantificationally, which follows a power law function. By designing the impact energy (or initial loading rate) in experimental tests conducted by split Hopkinson pressure bar (SHPB), the deformation-to-fracture process related with the inputted strain energy density or with deformation strain during a dynamic loading is observed through the post-test analyses. The ductile damage and brittle fracture characteristics as well as the tolerant cracking mechanisms are illustrated. This work is full of interest to develop a light-weight transparent protective polymer composite material against a high-speed impact loading. [ABSTRACT FROM AUTHOR]

Two types of Ottawa sand (ASTM C778 #20-30 graded sand, denoted OS1, and C109 ASTM #C778 graded sand, denoted OS2) with different particle size distributions were tested in a series of dynamic uniaxial strain experiments using a modified split Hopkinson pressure bar (SHPB) system. The pulse shaper technique was employed to achieve the dynamic force balance and constant strain rate in the sand specimen. The effects of the strain rate, initial void ratio and moisture on the dynamic compression response of sand were examined. Two types of dynamic behavior occurred in the dry sand: solid-like and fluid-like behavior. The OS1 samples exhibited a fluid-like response at all initial void ratios, whereas the OS2 samples exhibited a solid-like response for all void ratios. This difference between the two sands may be due to the difference in the particular size distributions of OS1 and OS2. The initial elastic response of the dry sand samples seemed to be independent of the strain rate. The strain rate effects became more apparent after particle crushing and particle rearrangement began. Under a high degree of saturation, the strain rate effects were immediately apparent, even at lower strains. The dynamic response of sand was remarkably linear until the peak strain was reached. [ABSTRACT FROM AUTHOR]

In this research, the dynamic response and energy absorption characteristics of four different types of commercially available glass have been investigated experimentally. Soda lime, starphire, borosilicate, and fused silica were characterized using a Dynatup 8250 drop weight impact test system, and a Split Hopkinson Pressure Bar (SHPB). In the low-velocity punch-shear experiments, similar trend has been observed for all glass types, while starphire and borosilicate exhibited the highest total energy absorption. High strain-rate SHPB compression tests were carried out on cylindrical glass samples at two different strain-rates. Borosilicate showed higher failure strain, compressive strength, and energy absorption compared to the other glass types. The SHPB compression results indicated high dependency of mechanical behavior of glass materials to strain-rate. The effects of surface flaws on dynamic mechanical behavior of borosilicate glass under SHPB compression loading were also investigated. [ABSTRACT FROM AUTHOR]

Abstract: Glass fiber polymer composites embedded with tetra-needle-like zinc oxide (ZnO) nanowhiskers were prepared. The prepared composites exhibited excellent mechanical properties after the effective dispersion of ZnO nanowhiskers in the resin. The static and dynamic compressive properties of the composites were tested in the thickness and in-plane directions. The macro- and microfracture morphologies of the damaged specimens were obtained by using a scanning electron microscope. The results show that the compressive properties of the composites could be significantly affected by strain rates. As the strain rate increases, the composites have a higher strength. The compressive properties of the composites are affected by the content of ZnO nanowhiskers in the resin. The high strength of the composites can be attributed to the three-dimensional structures of ZnO nanowhiskers and the corresponding stress transfer. [Copyright &y& Elsevier]

• Replacing sand in mortars by waste iron powder enhances the dynamic performance. • Elongated iron particulates act as micro-reinforcements improving energy absorption. • SHPB mortar experiments corroborate enhanced dynamic strength and energy absorption. • Microstructure guided multiscale FEA predicts rate dependent constitutive response. • Correlation of simulated and SHPB dynamic response parameters validates framework. An experimental and numerical evaluation on the dynamic compressive response of mortars containing up to 20% waste iron powder as sand replacement is presented in this paper. The dynamic response is evaluated using split Hopkinson pressure bar (SHPB) apparatus under high strain rates (up to 250/s). The elongated iron particulates present in the iron powder-incorporated mortars warrant significantly improved compressive strength and energy absorption capacity at high strain rates. Multiscale numerical simulations are performed with a view to develop a tool that facilitates microstructure-guided design of these particulate-reinforced mortars for efficient dynamic performance. The dynamic compressive response of particulate-reinforced mortars is simulated adopting a numerical approach that incorporates strain rate-dependent damage in a continuum micromechanics framework. The simulated dynamic compressive strengths and energy absorption capacities for mortars with various iron powder content exhibit good correlation with the experimental observations thereby validating the efficacy of the simulation approach. [ABSTRACT FROM AUTHOR]