Strain Rate Impact Research Articles

Experimental and numerical validation of high strain rate impact response and progressive damage of 3D orthogonal woven composites

Advanced three-dimensional (3D) woven composites for aerospace and automotive applications are commonly subjected to complex dynamic environments involving vibrations and impacts, resulting in examining their impact properties is extremely important. This paper first experimentally discussed the influences of strain rates, weft yarn densities and loading directions on the impact performances and failure mechanisms of 3D orthogonal woven composites (3DOWCs). Secondly, full-scale finite element models were developed to predict the stress distribution and interfacial damage evolution process. The predictions were well in agreement with the experimental results. This research revealed that the impact characteristics exhibited strain rate sensitivity. With increasing weft yarn densities, the high strain rate impact behaviors also improved. Particularly, the warp impact strength of 3DOWCs with a weft yarn density of 2 yarn/cm (W5-2) at 812 s−1 was 17.4% and 24.0% higher than that of 3DOWCs with a weft yarn density of 1.5 yarn/cm (W5-1) at 822 s−1. Meanwhile, warp impact strength consistently exceeded to that of the weft impact strength. Additionally, strain rates, weft yarn densities, and loading directions dramatically affected the stress distribution and interfacial damage evolution process of 3DOWCs. Significant warp yarns fracture and matrix cracking were the principal failure patterns in the warp impact, whereas the damage in the weft impact was dominated by localized fracture of weft yarns and interfacial debonding.

Effects of high temperature and strain rate on the impact-induced inter-laminar shear behavior of plain woven CF/PEEK thermoplastic composites

This paper aims to investigate the interlaminar shear properties and failure mechanisms of plain woven carbon fabric/polyetheretherketone (CF/PEEK) thermoplastic composites under high strain rate impact loads at different temperatures (25°C, 120°C, 295°C). A reliable hot air flow heating method with SHPB is creatively employed for short beam shear experiments. A multi-scale model was developed to predict the impact behavior of plain CF/PEEK composites. Both results show that the thermoplastic composites have strong strain rate and temperature dependence, and which are more sensitive to temperature effect. As the temperature increases, the thermoplastic composites are mainly affected by the softening effect of the matrix due to the glass transition temperature. The shear modulus and peak stress appear to decline at high temperatures, while the failure strain tends to increase. The damage mode changes from interlayer delamination cracking at the glassy state to shear fracture and fiber pullout at a highly elastic state. As the strain rate increases, the failure strain decreases, while the shear modulus and peak stress show the opposite trend. Fiber bundle breakage, debonding, matrix cracking, and significant interlayer delamination occur at high strain rates.

Impact response and constitutive model of basalt-polypropylene fiber-reinforced coral aggregate concrete

Basalt-polypropylene fiber-reinforced coral concrete (BPFRCAC) is a popular choice for engineering materials in the reef environment, but the dynamic behavior of BPFRCAC under extreme dynamic loads remains unclear. This study explores the impact response of BPFRCAC at strain rates ranging from 31 to 141 s−1 using split Hopkinson pressure bar (SHPB). It examines the effects of strain rate on the dynamic mechanical properties of BPFRCAC, and establishes quantitative models of the relationship between the strain rate and key mechanical parameters, including dynamic compressive strength, critical strain, dynamic elastic modulus, and toughness index. The results showed that these properties of BPFRCAC are significantly influenced by the strain rate, showing increases that correlate with the strain rate. The addition of basalt fibers (BF) and polypropylene fibers (PF) not only mitigates the failure extent of BPFRCAC but also enhances the strain rate's impact on its dynamic compressive strength and dynamic modulus of elasticity, particularly when both fibers are mixed. The failure modes of BF and PF depend on the strain rate; at lower strain rates, the probability of fiber pull-out is higher than at higher strain rates, where BF and PF are more likely to snap. A viscoelastic dynamic damage constitutive model suitable for BPFRCAC is proposed, which accurately describes the dynamic mechanical behavior of BPFRCAC. These findings provide important design insights into the use of BPFRCAC under impact conditions, and promote its wide application in reef construction projects.

A finite deformation formulation for amorphous glassy polymers under moderate and impact strain rates: Application to adhesive films

This work describes a novel finite strain hypo-elastic formulation for amorphous thermoset polymers working in the glassy regime. The constitutive formulation is able to describe time and pressure-dependent behaviour under loading rates ranging from quasi-static to impact-type loading conditions and to account for thermo-mechanical coupling effects. A non-linear pressure dependent potential function is introduced to capture the non-associative visco-plastic potential flow for volumetric plastic strain control. The formulation also incorporates an internal state or deformation resistance variable to enable the description of the polymer hardening — softening behaviour, as well as a novel relation for the dissipative fraction of the plastic work in terms of the equivalent accumulated plastic strain. The constitutive model is formulated within a finite strain kinematics framework, and full details of its numerical implementation into the finite element method using a fully implicit Euler Backward algorithm are given. Model calibration is carried out for three different thermosetting resins (PR520 and RTM6 Epoxies, and MMA adhesives).To illustrate the model capabilities, two case studies are investigated: (i) the de-formation behaviour of epoxy under moderate and impact-type loading conditions under isothermal and fully adiabatic conditions, and (ii) the fracture behaviour of adhesive layers used to bond stiff metallic substrates. Results on RTM6 epoxy show that at, e.g., 60% true strain, 48.5% of the rate of plastic work is dissipative, and that the corresponding predicted increase in temperature due to the locally dissipated heat is consistent with published calorimetry data on a similar thermoset polymer. It was also found that, by coupling the proposed constitutive model with a cohesive zone model, it was possible to predict accurately the effect of an MMA adhesive layer thickness and pressure-dependency on the growth of an interfacial crack between the MMA adhesive and the metallic substrates. The proposed model should constitute a generic phenomenological formulation for the mechanical behaviour prediction of a wide range of thermoset polymers under confined and quasi-adiabatic conditions such as in composites and adhesive joints.

Dynamic behaviors of nickel coated carbon nanotubes reinforced ultra-high performance cementitious composites under high strain rate impact loading

Understanding the dynamic mechanical behaviors of materials is a prerequisite for reliably analyzing and predicting the dynamic response of structures, which is of great significance for transportation infrastructure and military engineering subjected to extreme loads, particularly dynamic loads at high strain rates. Nickel coated multi-walled carbon nanotubes (Ni-MWCNTs) show promise as a reinforcement to modify the dynamic mechanical behaviors of ultra-high performance cementitious composites (UHPCC). Because Ni-MWCNTs combine the high tensile strength and large aspect ratio characteristics of fibers with the nano effect of nanomaterials, as well as have excellent dispersibility due to the nickel plating on the CNTs’ surface, they effectively improve the dynamic mechanical properties of UHPCC under impact loading at high strain rates of about 100 s−1/300 s−1/500 s−1 and reduce the brittle damage degree of composites. The maximal increase in dynamic compressive strength and energy absorption capacity of UHPCC reaches 47.9% and 68.2%, respectively. This enhancement effect arises from that Ni-MWCNTs improve the microstructure and form multiple fine cracks, resulting in an increased energy consumption required for crack formation, propagation and coalescence. Additionally, the dynamic mechanical properties of Ni-MWCNTs reinforced UHPCC exhibit noticeable strain rate effects. Consequently, a strain rate-dependent logarithmic functional dynamic increase factor model and dynamic constitutive model of UHPCC filled with Ni-MWCNTs are modified herein for predicting and modeling the dynamic mechanical behaviors of composites.

The High Strain Rate Response of A Bio-Mimetic Composite Plates

Biological materials are often viewed as composites, consisting of weaker components arranged hierarchically, leading to exceptional mechanical capabilities that are challenging to replicate in synthetic materials. Natural shape and structure develop through the process of striving for improved performance. This paper will provide a summary of observations from experiments conducted on a composite material designed to closely mimic a sophisticated multifunctional biological structure. The Split Hopkinson Pressure Bar (SHPB) was utilized to test strain rates ranging from 102 s-1 to 104 s-1, providing reliable and comprehensible data for analyzing the behavior of the composite material at high strain rates. The Split Hopkinson Pressure Bar (SHPB) device is frequently utilized for evaluating metals and other materials with high strength and mechanical resistance. This study will detail the changes made to a standard Split Hopkinson Pressure Bar (SHPB) apparatus for testing low impedance materials. An aluminum sample was seen to lose its specific stiffness as impact strain rate increased, but the produced material continued to improve.

Complete constitutive model of CFRP including continuous damage in low strain rate compression and temperature generation in high strain rate impact

AbstractThis paper reports a method to construct the complete constitutive model of carbon fiber‐reinforced plastic (CFRP) by distinguishing the strain rate state and modifying the material stiffness. In quasistatic (low strain rate) compression, the initial nonlinear effect caused by the material defects was described by introducing an nonlinear increasing factor. In dynamic (high strain rate) impact, the nonlinear strengthening effect was described by introducing the dynamic amplification factors of stress and strain based on the reference state. Considering the instantaneous temperature rise obtained from the impact work–temperature generation equation and the influence of temperature on modulus and strength, the coupled thermomechanical constitutive models combining the strain rate effect and the temperature effect were established. The user‐defined material subroutines (VUMAT) were developed, and then these constitutive models were verified by finite element analysis (FEA). Finally, the developed material subroutine was applied to predict the impact penetration of CFRP laminates, and the results show that the opening holes, damage and energy dissipation are in good agreement with the reference experiment. This work comprehensively analyzed the construction method of CFRP constitutive models, which would provide a guidance for the coupled thermomechanical behavior under dynamic impact.Highlights An anisotropic continuum mechanical constitutive behavior considering strain rate effect and damage evolution behavior was established. A macroscopic anisotropic constitutive model including the coupled impact temperature generation‐mechanical behavior was established. Combined with the incremental finite element method, the three‐dimensional user‐defined material subroutines (VUMAT) were developed and verified. The thermomechanical impact penetration behaviors of CFRP laminates was predicted, and the stress field, temperature field and failure characteristics were visualized.

Nanoscale phase transition in impact indented Mo/Cu thin films

The study reveals a size effect in deformation mechanisms via unique structural transitions in sputter deposited fcc/bcc nanolayers under high strain rate impact nanoindentation as layer thickness is reduced from around 100–200 nm to around 5 nm. The indented 5 nm Cu/5 nm Mo multilayer films characterized via cross-sectional scanning/transmission electron microscopy have revealed a phase transition in the 5 nm thick Mo layers from BCC to a coherent metastable FCC structure and fine deformation twins in the 5 nm Cu layers inside a shear band that is approximately 500 nm long and inclined to the layer interfaces. In contrast, thicker layers, 80 nm Cu/180 nm Mo, show different deformation behavior with uneven layer thickness reduction, shearing of Cu layers, and bending of the columnar Mo grains beneath the indentation without any sign of shear band and localized phase transformation.

Study on the impact resistance of steel fiber-reinforced self-compacting concrete after high temperature

The present study explored the dynamic mechanical properties of steel fiber-reinforced self-compacting concrete (SFRSCC) after a high temperature. The impact test was conducted using a φ80 mm split Hopkinson pressure bar (SHPB) device, with a focus on the factors of influence and the regularity of steel fiber content (0.5 %, 1.0 %, and 1.5 %), impact strain rate (55 s−1, 90 s−1, and 140 s−1), and temperature (20 °C, 300 °C, 600 °C, and 900 °C) on the failure form, dynamic strength, impact toughness, and dynamic increase factor (DIF-σ) of SFRSCC after high-temperature exposure, and the mechanism analysis based on the results of the SEM examination. The impact test results revealed the following: (1) With the increase in the steel fiber (SF) content, the dynamic strength (fp) of the SFRSCC exhibited a further evident growth trend after high temperature compared to that at normal temperature reaching 105 % and the toughness index also increased by more than 20 %. (2) While the effect of SF content on DIF-σ of SFRSCC was not significant under normal temperature conditions after high-temperature exposure, the DIF of SFRSCC can increase by over 40 % with the increase of SF content. In addition, the strain rate effect was also further significant, and the DIF-σ can increased by about 30 % after high-temperature treatment compared to normal temperature. (3) A prediction formula was proposed for DIF-σ of SFRSCC after high temperature, and the results were in good agreement with the results of the impact test. This prediction formula can better provide theoretical data support for disaster prevention and reduction in subsequent projects. The findings of the present study would serve as a valuable reference for subsequent research on the impact resistance of SFRSCC after high-temperature exposure.

Particle size distribution of aggregate effects on the dynamic compressive behavior of cement waste rock backfill

Cement waste rock backfill (CWRB) is an essential component of green mining. Recent studies have demonstrated that the CWRB can slow surface settlement and provide economic advantages. However, there has been only limited research into the susceptibility of CWRB to dynamic impacts such as rock bursts, especially as mining depth increases. This study aims to investigate the dynamic peak stress, elastic modulus, and dissipated energy of CWRB specimens using a split Hopkinson pressure bar system. The results demonstrated that the responses of aggregate with different particle size distributions to the system’s impact strain rate (ISR) were inconsistent. Specifically, the highest dynamic peak stress of 23.71 MPa was achieved for the CWRB (Talbot index = 0.6) at a low ISR (30 s−1–35 s−1) and 62.33 MPa for the CWRB (Talbot index = 0.4) at a high ISR (40 s−1–50 s−1). A strain nephogram and fractal dimension analysis further suggested that the CWRB (Talbot index = 0.4, 0.6) could continue to provide partial compressive resistance after impact. Moreover, a compressive model was developed to determine the “change point” between the low and high ISR. The model indicated that different particle size distributions influenced the porosity, and at a high ISR, the pore structures further worsened the dynamic compressive behavior of CWRB. This study not only enhances our understanding of the compressive performance of CWRB under dynamic impact, but also contributes to the safety and efficiency of filling mining operations. In addition, it offers a theoretical explanation of the effects on the dynamic compressive behavior of CWRB.

Dynamic mechanical behavior of additively manufactured bio-inspired metallic lattice structure subjected to high strain rate impact loading

The bio-inspired sponge lattice structure (SLS) and frame lattice structure (FLS) are fabricated by laser powder bed fusion using 316 L stainless steel. The static and dynamic mechanical behavior of the two structures is investigated experimentally by universal testing machine and direct impact Hopkinson bar (DIHB) devices respectively. The deformation evolution of the structures is also captured by the digital camera. Meanwhile, numerical simulations are performed by ABAQUS to further explore the mechanical properties of the lattices. Subsequently, the influence of impact velocity on the deformation modes and specific plateau stress of the lattice structures is investigated. The results show that the SLS presents a stable mechanical response under both quasi-static and dynamic loadings compared with the FLS, while auxeticity is observed in the SLS under static and low-speed impact. Within the considered impact velocity, the dynamic sensitivity of the SLS is derived from the strain rate effect of the base material. The plateau stress of SLS under dynamic loading is higher than that of the FLS, which indicates that the SLS may not be conducive to saving from harm to the protected targets under dynamic loading.

Effect of MWCNT on CFRP impregnated with shear thickening fluids under high strain rate impact

This study investigates the effect of multi-walled carbon nanotubes (MWCNT) on the high strain rate properties of carbon fiber reinforced polymer (CFRP) fabric impregnated with shear thickening fluids (STF). Three GFRP-STF and twelve GFRP-MWCNT/STF composite specimens were conducted using a split Hopkinson pressure bar (SHPB). Spherical silica nanoparticles (20.0 wt%) and polyethylene glycol were used to prepare silicon-based-STF (SiO2/STF). On this basis, MWCNT with 0.4, 0.8, and 1.2 wt% were further used to synthesize the MWCNT/STF, respectively. The SHPB test showed that MWCNT/STF has a more significant strain rate effect, with stress increases of 71.1%, 57.5%, and 26.0% under 3800 s−1, 5100 s−1, and 6100 s−1, respectively. The results also showed that MWCNT significantly improved the yield stress and strain energy absorption of SiO2/STF under a high strain rate. The maximum yield stress increase was 71.1%, and the maximum increase in strain energy absorption was 229.1%. The results of CFRP-MWCNT/STF revealed that MWCNT/STF treatment enhanced the high strain rate impact properties of CFRP-SiO2/STF. The improved effect is up to 27.9%, 133.6%, and 165.7% in yield stress, impact toughness, and energy absorption efficiency, respectively. The mass fraction of MWCNT significantly affects the impact properties of CFRP-MWCNT/STF under high strain rate loading, but this effect decreases with the increase of strain rate. Thus, CFRP-MWCNT/STF is more suitable for application in a high strain rate impact environment than CFRP-SiO2/STF.

Susceptibility of adiabatic shear band formation in AZ31B magnesium alloy during high strain rate impact

Susceptibility of adiabatic shear band formation in AZ31B magnesium alloy during high strain rate impact

Effects of fiber and rubber materials on the dynamic mechanical behaviors and damage evolution of shotcrete under cyclic impact load

Dynamic loads in underground construction environments can significantly damage supporting structures. The mechanical behavior of shotcrete under high strain rate impact has received significant attention. However, few researchers have investigated the performance degradation law, damage evolution process, and failure mode of shotcrete under cyclic impact load. This study utilized the split Hopkinson pressure bar (SHPB) to conduct cyclic impact loading experiments on shotcrete reinforced with copper-plated steel fiber (CSF), basalt fiber (BF), polypropylene fiber (PF), and rubber particles (RP). The addition of reinforcing materials significantly improved the dynamic mechanical properties of shotcrete. Under cyclic impact, the stress-strain curves of reinforced shotcrete basically coincided in the elastic deformation stage. As the content of the reinforcing materials increased, the dynamic mechanical properties of the shotcrete improved. The performance of fiber-reinforced shotcrete improved under the compaction effect caused by the first impact. Only rubber shotcrete sustained 6 impacts under cyclic constant impact pressure. Based on the ultrasonic velocity obtained by non-destructive testing, a cumulative damage evolution model during cyclic impact was established. The incorporation of RP effectively slowed down the damage evolution rate and increased the shotcrete's bearing capacity for cumulative damage. This paper conducted a comprehensive comparative analysis and concluded that the addition of rubber particles at a content level of 5% was the most cost-effective option to enhance the dynamic mechanical properties of shotcrete. The findings provide a theoretical reference for underground engineering supporting structures subject to long-term cyclic dynamic loading.

The effect of high strain rate impact in Yttria stabilized zirconia

Yttria stabilized zirconia (6-8YSZ) is widely used as a top coat in Thermal Barrier Coatings (TBCs) to protect metallic substrates. These coatings are exposed to severe high strain rate fields along their life, for example during the impact of debris happening in service or during coating removal in repair processes. In this work a water jet and a high strain rate nanoindenter are used to understand the effect of the strain rate (from 10-3 to 108 s−1) on the behaviour of 8YSZ at a small scale. It is observed how, at extremely high strain rates (106–108 s−1), the material suffers from a brittle-dominated failure which induces localized phase transformation. At lower strain rates (10-3−1 s−1), plasticity dominates, and phase transformation is not observed.

Experimental and numerical investigation on interface microstructure and phase constitution of radiation resistant Pb/316L stainless steel explosive welded composite plate

As one of the shielding materials, lead (Pb) and its alloy exhibit excellent ray absorption and radiation shielding ability due to its high density and atomic mass. In this work, the explosive welding technique was successfully performed to join Pb/316L dissimilar metals. To revel the microstructure characteristics and phase constitution of the joining interface, the electron backscattered diffraction test and numerical simulation were carried out. It was concluded that the slight waveform structure without obvious defects or cracks was obtained at the explosive welded interface. The fine grains zone, sub-grains and twin structures were formed due to the severe plastic deformation. Meanwhile, the recrystallized structures, substructures and deformed structures were also confirmed at the joining interface during the high strain rate impact. In addition, five different deformation textures and recrystallization textures were confirmed due to severe plastic deformation and dynamic recrystallization. Furthermore, the numerical simulation results also showed a slight waveform structure at the Pb/316L explosive welded interface, which was consistent with the experimental results.

Design and mechanical analysis of shear thickening fluid/polyurethane composite sandwich

In this paper, high density rigid polyurethane foam is used as sandwich skeleton and shear thickening fluid as material core. A shear thickening fluid/polyurethane sandwich structure with light impact resistance was designed and fabricated. High strain rate impact test was carried out. It was found that STF-2/PU reached the peak load of 4978N in 13 ms after receiving 20 J impact energy, and the energy absorption ratio was as high as 43%. The shear thickening fluid/polyurethane honeycomb sandwich foam prepared by secondary foaming process has stable structure and can effectively absorb impact energy to achieve good protection effect.

Influence of pre-twinning on adiabatic shear sensitivity of AM30 magnesium alloy

The effects of volume fraction of pre-introduced {10−12} extension twins on adiabatic shear sensitivity of AM30 magnesium (Mg) alloys were studied via dynamic compression experiments using a split Hopkinson pressure bar (SHPB). The relationship between adiabatic shear sensitivity and volume fraction of twins was analyzed by combining mechanical responses and microscopic analysis. The recrystallization mechanism in the adiabatic shear bands (ASBs) was investigated as well. According to the results, the adiabatic shear sensitivity of AM30 Mg alloys increased with the increase in the volume fraction of twins, while the degree of recrystallization in the shear band decreased. The recrystallization mechanism in the shear band was found to obey rotational dynamic recrystallization (RDRX). • The effect of volume fractions of {10–12} extension twins on the adiabatic shear sensitivity of AM30 magnesium alloys under high strain rate impact was investigated in the first time. • The adiabatic shear sensitivity of the AM30 alloy increased with the increasing volume fraction of extension twins. • The recrystallization in shear bands occurred by rotational dynamic recrystallization based on the calculation of dynamic equation.

The Effect of Dynamic Fracture Strain on the Structural Response of Ships in Collisions

As ship collisions and grounding accidents lead to human injury and damage to the environment and property, more accurate predictions of structural damage to ships under impact loads are needed. Currently, to determine structural behaviors, finite element analysis (FEA) is frequently adopted. However, it is recommended to pay attention to material properties in FEA because structural damage is sensitive to material properties such as yield strength, fracture strain, etc. While the strain rate (impact speed) is automatically considered for dynamic yield stress using the Cowper–Symonds equation or other methods, the pre-defined fracture strain is generally used as the dynamic fracture strain (DFS), which is not dependent on strain rate during the simulation. This assigned value of fracture strain may affect the extent of damage and structural response. In this study, the effect of the DFS on the structural damage from collisions was investigated to determine the relationship between the DFS and damage. Empirical formulas based on predictions of damage by various events were developed as a function of the DFS and initial impact speed. The results of this study explained the effect of the DFS on the structural damage and determined the upper and lower bounds of damage by collisions.

The microstructure evolution and deformation mechanism in a casting AM80 magnesium alloy under ultra-high strain rate loading

Ultra-high strain rate impact tests were conducted by Split-Hopkinson pressure bar to investigate the microstructure evolution and impact deformation mechanism of a solution treated casting AM80 Mg alloy at 25, 150 and 250 °C with a strain rate of 5000 s −1 . The microcrack and dynamic recrystallization (DRX) preferentially nucleate at grain boundary (GB) and twin boundary (TB), especially at the intersections between GBs and TBs, and then propagate along twin direction. In contrast, the adiabatic shear bands preferentially occur at high-density twined regions. At 25 °C, the dominated deformation mechanisms are basal slip and twinning. As deformation temperature increases to 150 and 250 °C, the deformation gradually shifts to be dominated by a coordinated mechanism among non-basal slip, twinning and DRX. The flow stress behavior and deformation mechanism indicate that the degree of decrease in flow stress with temperature is associated with the change of deformation mode.