Impact Compression Research Articles

Ballistic response of a high-strength steel

Quasi-static compression/tension, dynamic compression/shear mechanical property tests, fracture morphology characterization, dynamic response experiment, numerical simulation, and calculation of the ultimate penetration velocity of the high-strength steel under the impact of large mass low-velocity fragments and small mass high-velocity fragments were carried out to study the ballistic performance of high-strength steel used for armor vehicle protection and clarify its dynamic response under Ballistic impact. The fracture mode of the high-strength steel under dynamic impact compression and shear was shear failure. A large number of fine parabolic shear dimples were formed on the fracture surface. The high-strength steel had an obvious strain rate strengthening effect and adiabatic shear sensitivity. The plug formed under the low-velocity impact of a large mass fragment was a cone shape, and the impact area of the target plate underwent slight bending plastic deformation. The damage of the fragment to the target plate includes both adiabatic shear failure and ordinary shear failure. Under the high-velocity impact of small mass fragments, the fragments were seriously deformed and destroyed, and the damage model of the target plate is adiabatic shear failure.

Modelling low-velocity impact damage and compression after impact of 3D woven structures considering compaction

A novel finite element modelling approach is presented which incorporates representative binder yarn compaction, for simulating the low-velocity impact (LVI) and compression after impact (CAI) response of 3D woven layer-to-layer carbon/epoxy composite architectures. Simulations of out-of-plane drop-weight impact tests were performed at energies of 32 J and 42 J. Warp and weft layers were modelled as continuous plies and three different approaches were explored to model the binder reinforcement; (i) with a rectangular cross-section and non-compacted, (ii) with an elliptical cross-section and non-compacted, and (iii) an elliptical cross-section which accounts for compaction. Predictions were compared with experimental results from literature and it is shown that modelling the binder reinforcement as an elliptical cross-section with compaction leads to a predicted damage area, on the impacted side, which is within 2%, and the non-impacted side within 6% of experimental measurements. The predicted CAI strength is within 11% of the experimental values.

Soil particle size-dependent constitutive modeling of frozen soil under impact loading

In this study, the soil particle size dependence of the impact dynamic mechanical properties of frozen soil was investigated using a split Hopkinson pressure bar, and the meso-deformation mechanism of frozen soil was analyzed via electron microscopy. Under impact loading, the dynamic stress-strain curves of frozen soil showed strain hardening, strain softening, strain rate-temperature sensitivity, and soil particle size dependence, and the soil particle size dependence of frozen soil was considered to be significantly influenced by non-uniform meso-deformation, which primarily appeared in the form of microcracks surrounding the coarse particles. A constitutive model comprising a multiplicative hardening law was proposed, and soil particle size dependence was introduced through the equivalent strain gradient of the soil cell element. The impact compression process of frozen soil was simulated in ABAQUS/Explicit using the proposed model, and the mechanism of frozen soil deformation was summarized by the finite element analysis: the stress concentration around coarse particles induces the initiation of microcracks, the propagation of microcracks forms a crack network, eventually leading to the softening behavior of frozen soil.

Low-Velocity Impact and Residual Compression Performance of Carbon Fiber Reinforced Composite Stiffened Plates

Low-Velocity Impact and Residual Compression Performance of Carbon Fiber Reinforced Composite Stiffened Plates

The Effect of Different Fibers on Granite Residual Soil Reinforced with Alkaline Solution

This study explores the reinforcement effect of different fibers in an alkaline solution on the mechanical properties of granite residual soil using the single variable method. The macroscopic mechanical properties of the reinforced samples were studied using the unconfined lateral compressive strength test and the drop-weight load test, while the microscopic properties were characterized using techniques such as SME and XRD. The results indicated that the greatest reinforcing effect was attained when the ratio of SiO2/Na2O in the alkaline solution was 0.5 mol with the compressive strength of 4402.85 kPa. At the time, the reinforcing effect of glass fiber in an alkaline solution on granite residual soil was superior to that of basalt fiber. The inclusion of glass fibers and an alkaline solution of 0.5 mol SiO2/Na2O into the granite residual soil exhibited the best capacity for reinforcing, with the maximum impact load and compression reaching 120 kN and 12.1 mm, respectively. The findings of SME analysis revealed that GRS included a significant amount of kaolinite, which, when decomposed in an alkaline solution, generated a gel substance that bound the fibers and soil together and filled the pores between them, thereby enhancing the sample’s compactness. XRD results demonstrated the formation of gel and a small amount of geopolymer in the soil under the alkaline solution of 0.5 mol SiO2/Na2O, which tighten the binding between soil particles and fibers and increase the overall strength.

Comparison of the Low-Velocity Impact Responses and Compressive Residual Strengths of GLARE and a 3DFML

The impact performance and compression after impact characteristics of 2D and 3D fiber metal laminates (FMLs) are investigated both experimentally and numerically. Commercial-grade GLARE3A-3/2-0.3, and a recently developed FML, which incorporates a unique 3D glass fabric, are used in the study. Both FMLs have similar areal densities. The specimens are subjected to impact loading at three energy levels-low, intermediate, and high. The test results indicate that GLARE is slightly more resilient under impact compared to the 3DFML. However, since GLARE is much thinner than the 3DFML, the two-material systems exhibit very different failure modes. GLARE and 3DFML lost up to 62.6% and 41.5% of their original compressive load-bearing capacity, respectively. Robust and accurate finite element models are developed that can predict the damage evolution and failure modes of both FMLs. Knowing the level of reduction in the residual load-bearing capacity of a material resulting from an impact is of practical importance when assessing the service life of materials. However, further exploration would be required to determine how the information obtained through testing relatively small-sized specimens in a laboratory environment can be extrapolated to larger real-life structural components.

Research on the Impact Mechanical Properties of Real-Time High-Temperature Granite and a Coupled Thermal–Mechanical Constitutive Model

Studying the mechanical behavior of rocks under real-time high-temperature conditions is of great significance for the development of energy caverns, nuclear waste disposal projects, and tunneling engineering. In this study, a real-time high-temperature impact compression test was conducted on Sejila Mountain granite to explore the effects of temperature and external load on its mechanical properties. Based on the concepts of damage mechanics and statistics, a coupled thermal-mechanical (T-M) damage constitutive model was established, which considers the temperature effect and uses the double-shear unified strength as the yield criterion. The parameter expressions were clarified, and the accuracy and applicability of the model were verified by experimental data. The research results indicated that high temperatures had an obvious damaging and deteriorating effect on the strength of the granite, while an increase in impact velocity had an enhancing effect on the strength of the granite. The established constitutive model theoretical curve and test curve showed a high degree of agreement, indicating that the coupled T-M model can objectively represent the evolution process of damage in rocks and the physical meaning of its parameters is clear.

Initial Response of Pentaerythritol Tetranitrate (PETN) under the Coupling Effect of Preheating, Shock and Defect via the Molecular Dynamics Simulations with the Multiscale Shock Technique Method.

The initial response of PETN under the coupling of preheating, impact and defects was simulated by Multiscale Shock Technique (MSST) method and molecular dynamics. The temperature change of PETN during impact compression can be divided into three stages: (1) the elastoplastic change of the system caused by initial compression; (2) part of PETN decomposes and releases energy to raise temperature; (3) a secondary chemical reaction occurs, resulting in rapid temperature rise. Under the given conditions, a higher initial preheating temperature will lead to faster decomposition of PETN; The existence of defects will accelerate the decomposition of PETN molecules; Coupling the highest preheating temperature with defects will lead to the fastest decomposition of PETN molecules, while in the defect-free PETN system with a preheating temperature of 300 K, the decomposition of PETN molecules is the slowest. For the case of Us = 8 km·s-1, the effect of defects on the initial PETN reaction is greater than the initial preheating temperature; When the impact velocity is greater than 9 km·s-1, the impact velocity is an important factor affecting the decomposition of PETN molecules. For Us = 10 km·s-1, NO2 is the main initial product in the defective PETN crystal, while in the perfect PETN crystal, it is the combination of NO2 and HONO. The chemical reaction kinetics analysis shows that the preheating temperature and defects will accelerate the decomposition of PETN. The higher the preheating temperature, the faster the decomposition of PETN. For the case of Us = 7 km·s-1, 8 km·s-1 and 9 km·s-1, the existence of defects will increase the decomposition rate by more than 50% regardless of the initial preheating temperature. In the case of Us = 10 km·s-1, the improvement of decomposition rate by defects is not as significant as the initial preheating temperature.

Research on Particle Size and Energy Consumption Law of Hard Coal Crushing under Impact Load Based on SHPB Test

To study the particle size distribution and energy variation law of hard coal under a load, an impact compression test of hard coal specimens under different impact loading conditions was carried out using a Φ50 mm diameter Separate Hopkinson Press Bar (SHPB) test system. We implemented the theory of dynamic impact energy of rock to establish the calculation expression of hard coal impact crushing energy dissipation, and we established the Weibull distribution model of a crushing body to analyze the impact velocity in relation to the particle size distribution of hard coal crushing and crushing energy consumption. The results demonstrate that due to the different original states of the specimens, the damage to the specimens under static action is in the mode of conjugate plane shear damage, single bevel shear damage, and tensile damage. The damage process of the specimen under impact load loading is divided into three stages: elastic deformation, elastic–plastic deformation, and plastic softening, while the increase in the strain rate caused the peak stress of the specimen to increase. The Weibull distribution can characterize the impact crushing size distribution of hard coal specimens very well. The parameter of coal rock crushing degree is a power function that is influenced by the impact velocity; the greater the impact velocity, the higher the coal rock crushing degree, but the characteristic index of coal rock crushing fluctuates with the increase in impact velocity. As the impact velocity increases, the incident energy and reflected energy increase linearly, while the transmitted energy increases first and then decreases. The dissipation energy of coal rock crushing also increases linearly with the impact velocity. There is no obvious regular change between the energy dissipation rate of coal rock and impact velocity during impact damage, and the dissipated energy of macroscopic crushing only accounts for 10~20% of the incident energy; most of the energy is used for damping loss and damage loss.

Low-velocity impact behavior of injection over-molded short/continuous fiber reinforced polypropylene composites

Injection over-molded short/continuous fiber composites are getting attention in automotive industry due to their recyclability, light weight, good specific strength, short processing time and ability to make complex shaped structures. The low-velocity impact behavior and compression strength after impact of short glass fiber reinforced polypropylene (SGFPP) and quai-isotropic composites (QI) and injection over-molded short/continuous glass fiber polypropylene (OM) composites were investigated by drop-weight impact and compression after impact tests. The low-velocity impact tests revealed higher specific absorbed energy for OM specimens compared with SGFPP and QI specimens. The impact energy is dissipated in OM composites primarily through interface debonding, delamination and damage in the short fiber composite core. Whereas, SGFPP and QI specimens dissipated the energy by complete perforation and delamination, respectively. Although QI specimens can bear more compressive load after impact, the OM specimens exhibited higher specific compression strength after impact compared with SGFPP and QI samples.

Preparation and characterization of UHMWPE reinforced with polyester fibers for artificial cervical disc replacement (ACDR)

The purpose of this paper is to report on the preparation and improvement of a biocomposite material made from ultra-high molecular weight polyethylene for the replacement of natural discs. Such replacements are necessary due to intervertebral disc degradation as humans age, which can cause persistent pain due to nerve compression and high friction between vertebrae that can lead to vertebral corrosion. The material was shown to have excellent mechanical properties such as low coefficient of friction, and biocompatibility; however, it degraded with time due to wear failure. Moreover, The wear resistance was related to many factors, such as toughness. In the methodology of the current study, UHMWPE is reinforced with different percent of polyester (2, 4, 6, 8, 10%) to improve the mechanical properties of the polymer disc, thus enhancing its toughness and providing its high bearing ability for the load. The findings revealed that the tensile strength and modulus of elasticity improved by 43.415% and 34.286%, respectively, with the 6% polyester fibers due to the excellent entanglement between the matrix and reinforcing phase. The other mechanical properties, such as flexural strength and modulus, impact strength, fracture toughness, and compression strength, were also enhanced in this study. The highest value at 6% polyester fiber was found to be due to good bonding and adhesion between the polymer and polyester fibers. The Fourier Transformation Spectroscopy (FTIR) showed a shift on some peaks. The originality of this work is that the improvements due to the new bio-composite polymers for artificial implant cervical discs can open many applications in future for these materials.

Compression-After-Impact analysis of carbon/epoxy and glass/epoxy hybrid composite laminate with different ply orientation sequences

This article is a continuation study of the LVI and CAI response of the plain carbon fiber composite laminates and explores the experimental & numerical study of the post-impact damage propagation in carbon/epoxy and glass/epoxy hybrid laminate under compression. LVI (Low-Velocity Impact) tests are first carried out at three different energy levels, and the same specimens are put under a displacement-controlled compression test. The damage initiation and propagation in both impact tests and compression tests are studied using X-ray computed tomography. The results matched well with the results obtained from the finite element model, simulated using ABAQUS/explicit. The effect of the changing impact energy and the influence of the stacking orientation on post-impact damage propagation is studied. The strain maps during the compression tests are studied through Digital Image Correlation (DIC) technique based on which the stress–strain histories are plotted by using well-calibrated strain values. Upon completing the study, it is observed that the CAI (Compression-After-Impact) strength depends on the factors like properties of the constituent material, ply orientations and stacking sequence of the laminate. It is observed that even when the damage is barely visible on the surface of the specimen, compressive strength has been reduced drastically. The observed mode of damage propagation in CAI testing is buckling of the sub-laminates in the vicinity of the damage zone formed by the impact event. The size of the impact damage zone depends on the impact energy, which actually governs the CAI strength.

Freeze–Thaw Cycle Effects on the Energy Dissipation and Strength Characteristics of Alkali Metakaolin-Modified Cement Soil under Impact Loading

To investigate freeze–thaw cycle effects on the energy dissipation and strength characteristics of cement soils under impact loading, impact compression tests were carried out using a split Hopkinson pressure bar on cement soils under various freeze–thaw cycles (0, 1, 3, 6 and 10 times). The Zhu–Wang–Tang (ZWT) model was modified to predict the relationship between deformation and strength in cement soils under various test conditions. The obtained test results revealed that the freeze–thaw cycle number and impact pressure had significant effects on the fractal dimension, strength and absorbed energy of cement soils and there existed a critical freeze–thaw cycle number. It was found that the increase of the freeze–thaw cycle number gradually decreased strength and absorbed energy and increased the fractal dimension. When freeze–thaw cycle number was between 0–6, strength, fractal dimension and absorbed energy were significantly changed. For freeze–thaw cycle numbers greater than 6, the effects of the above factors were gradually alleviated. A modified constitutive model was able to accurately describe cement soil mechanical responses under high strain rate conditions, and the relative error between the predicted and experimental results was in the range of ±7%.

The effects of strain rate and strain on the deformation-induced grain refinement process and hardness evolution of a polycrystalline cobalt

In this study, the effects of strain rate and strain on the evolution of microstructure and hardness of a polycrystalline cobalt subjected to high-speed impact and quasi-static compression, with the strain rate of ∼ 103 s−1 and 3 × 10−3 s−1, respectively, were investigated. During high-speed impact, the high strain rate promoted the activation of various types of twinning: 101̅2, 101̅1, 112̅1 and 112̅2 twinning, as well as the 101̅1−101̅2 double twinning. Meanwhile, the temperature rise during high-speed impact activated the incomplete dynamic recrystallization. Deformation twinning, deformation-induced martensitic phase transformation and dynamic recrystallization contributed to the grain refinement. During quasi-static compression, dislocation slip and twinning dominated the deformation. Only 101̅2 twins with different orientations were triggered. The number of twins increased with the increase of strain, but was less than that in the high speed compressed sample. The high speed compressed samples exhibited higher hardness values compared with the quasi-statically compressed samples. The more pronounced hardening effect mainly accounted for the higher density of twins produced during high-speed compression. Although the recrystallization during high-speed compression may lead to strain softening, such softening effect was overwhelmed by the strengthening effect of grain refinement.

Improving the Mechanical Properties of Epoxy by Adding Sub-micron Cantaloupe Peel Fibers

The use of bio-fruit waste has more attention in recent years because of the low cost of bio-fibers and the protection of the environment. In this study, the epoxy was reinforced with fruit residues (cantaloupe peel powder) in proportions (1%, 2%, 3%, 4%, 5%, 7.5%, and 10% by weight) as results of mechanical tests such as impact, hardness, flexural and compression. Adding sub microns particle size cantaloupe peels particles with a weight ratio of 7.5% improves the epoxy mechanical properties, like impact strength, hardness, flexural strength, and compression strength by 59.43%, 5.8%, 45.7%, and 118.2%, respectively. Using X-ray diffraction, the crystallite size ( D) of cantaloupe peel the powder was about (3 nm). In this research, Scanning electron microscopy was used to examine the morphology of the (epoxy/7.5 % cantaloupe peel powder) composite and to interpret the improvement in epoxy mechanical properties.

Strategies to improve the impact resistance of self-compacting concrete (SCC) after freeze-thaw cycles

Three strategies including rubber particles, steel fibers and asphalt-coated coarse aggregate (ACCA) were introduced to improve the impact resistance of self-compacting concrete (SCC) after freeze-thaw cycles. The impact compression properties of SCC after 200 freeze-thaw cycles were investigated using a 75-mm split Hopkinson pressure bar (SHPB). The fineness modulus of residue (Mr) and impact toughness index (ITi) were defined to evaluate the impact-resistance performances of SCC. Results show that dynamic properties of SCC including peak stress, peak strain, Mr and ITi show remarkable strain rate effect. The decrease scale of Mr for SCC with modifying materials is considerably lower than that of the control group, indicating a less damage degree caused by freeze-thaw cycles. The ITi of SCC is greatly improved by three types of modifying materials, and the efficiency of improvement is ordered as: SCC-SF > SCC-ACCA > SCC-R. The average ITi decrease rate of SCC-R, SCC-SF and SCC-ACCA in all strain-rate range is 3.3%, 2.0% and 1.3%, respectively, which is much lower than that of SCC0 (7.8%), indicating a reduced impact toughness loss caused by freeze-thaw cycles. The enhancement of impact resistance for SCC with three types of modifying materials is highly related to their crack propagation effect during the impact compression process.

The Influence of Fly Ash Contents on Mechanical Properties and Energy Response of Concrete at a High Strain Rate

The dynamic uniaxial impact compression test was carried out by the Hopkinson pressure bar test system to test the dynamic mechanical properties of concrete with different fly ash contents ( P = 0 , 10%, 20%, 30%, 40%, and 50%) under 0.3 MPa air pressure. The influences of fly ash content variation on the mechanical characteristics, ductility characteristics (which were calculated according to the concrete ductility formula), energy dissipation characteristics, and surface specific energy variation characteristics (which were calculated by converting the fragments into spheres) of concrete were analyzed, respectively, and the influences of fly ash content variation on the fragment distribution and fractal features of concrete were obtained by statistical analysis. In addition, the application of concrete with the change of fly ash contents in rock burst mine was studied. The results showed that the dynamic peak stress, residual stress, ductility characteristics, fragments distribution, fractal dimension, transmitted energy, dissipated energy, and surface specific energy change significantly with the increase of fly ash contents under dynamic uniaxial impact compression. By analyzing the relationship between surface specific energy and concrete fragment distribution, it could be found that the energy dissipated by stress waves in concrete can be estimated by using the particle size distribution of the field fragments.

EXPERIMENTAL STUDY OF IMPACT COMPRESSION MECHANICAL PROPERTIES OF THE CELLULAR CONCRETE WITH CORAL SAND FINE AGGREGATE

The compressive behavior of the cellular concrete with coral sand fine aggregate was experimentally investigated under quasi-static and high-strain-rate loadings. Quasi-static tests at strain rate of 10-5/s were conducted using a servo-hydraulic material test system. Impacting tests at strain rates ranging from 70/s to 140/s were performed using Φ74 mm conic variable cross-sectional split Hopkinson pressure bar (SHPB) equipment. The strain rate effects on the compressive strength, elastic modulus, and peak toughness were studied. The results indicated that the compressive strength, elastic modulus, and peak toughness all increased with increasing strain rate and displayed clear strain-rate dependence. At high strain rates the compressive strength decreased with increasing the porosity, while the dynamic increase factor of compressive strength (DIF-f<sub>c</sub>) due to the pure rate effect showed a reverse tendency, which may contribute to more significant path altering effect in specimens with higher porosity.

A novel braiding method and impact behaviors of 3-D braided composite three-way integrated circular tubes

3-D braided composite three-way circular tubes are integrated seamless connected tubes used for high strength connecting joints. We developed a novel braiding method of ‘yarn-added, yarn realigned’ to prepare three-way tubular preforms. Low-velocity impact compressions (LVIC) along axial direction were conducted to find effects of branch length and braiding layers on impact damage with drop-weight tester, high-speed camera, Micro-CT and digital image correlation (DIC). It was found that the three-way braided tubes have uniform structure both at the branches and joint regions. There is shear band induced by the weakened interface appeared after the peak load and formed within 60 μs under impact. The ultimate strength was positively correlated with the impact energy and braiding layers, while negatively correlated with the branch tube length. The test results showed that the branch length affected the position of stress concentration, and the influence of braiding layers on the LVIC behaviors is more significant than that of the branch length.

Study on dynamic mechanical properties and constitutive model of granite under constant strain rate loading

A systemic understanding of the dynamic mechanical properties and dynamic constitutive model of granite is of great significance to the study of natural disaster prevention and protection of granite buildings. In the present study, constant strain rate loading tests of granite specimens under different impact velocities were carried out by using a shop-fabricated cylindrical conical striker and split Hopkinson pressure bar (SHPB) test system. The compressive strength of granite material increases with the strain rate, and therefore, a continuously smooth uniaxial dynamic strength criterion suitable for describing the changes in the dynamic increase factor (DIF) with strain rate was proposed and tested. The granite specimen under impact loading was intact when the strain rate was lower than 80 s−1, cracked when it was 80 to 90 s−1, fractured when it was 90 to 135 s−1, and crushed when it was over 135 s−1. Ultrasonic wave tests were performed to evaluate the damage caused by impact, and the quantitative relationship between the damage value and peak stress was established based on regression analysis. The results showed that the stress threshold causing damage was 50.15 MPa with a corresponding strain rate of 31.7 s−1 and a peak strain of 3670 microstrain. A new constitutive model describing the dynamic mechanical properties of granite was developed based on a nonlinear viscoelastic model (the ZWT model), and the constitutive parameters were then determined. A user-defined material subroutine named VUMAT of ABAQUS finite element software was applied to describe the established constitutive model and simulate the impact process of granite. The results confirmed that the developed constitutive model can well describe the prepeak dynamic mechanical properties of granite under impact compression.