Dynamic response and fracture of B₄C/6061 Al composites: experiments and simulations

In order to study the dynamic compression mechanical properties of engineering rock under high strain rate （100~102 S−1）loads, dynamic compression tests of three common engineering rocks (marble, sandstone and granite) taken from the Qinling Mountain are studied subjected to five different kinds of shock air pressure using Φ 100 mm split Hopkinson pressure bar test system improved with purple copper waveform shaper. The dynamic compression stress-strain curves, dynamic compressive strength, peak strain, energy absorption rate and elastic modulus of three rocks variation with strain rate are researched. The dynamic compression failure modes under different strain rates are analyzed. Then the three-dimensional numerical simulations of waveform shaper shaping effects and stress wave propagation in the SHPB tests are carried out to reproduce the test results. The research results show that the dynamic compression stress-strain curves show certain discreteness, and there is an obvious rebound phenomenon after the peak. With the increase in strain rate, the dynamic compressive strength, peak strain and energy absorption rate are all in a certain degree of increase, but the elastic modulus have no obvious change trend. Under the same strain rate, the dynamic compressive strength of granite is greatest while of sandstone is least. With the increase in strain rate, the margin of increase in peak strain and energy absorption rate of granite is greatest while of sandstone is least. The failure modes of the sample experience a developing process from outside to inside with the increase of strain rate.

Revisiting the Brazilian disc test with split Hopkinson pressure bar by high-speed digital image correlation analysis

Interface tensile and fracture behavior of the Ti/Al3Ti Metal-Intermetallic Laminate (MIL) composite under quasi-static and high strain rates

The punch shear behavior of 3-D biaxial spacer weft knitted E-glass/ vinyl ester composite was investigated at quasi-static (0.01/s) and high strain rates ranging from 1200 to 3200/s in wale and course directions respectively. The quasi-static shear behavior was tested on a MTS 810.23 material tester and was compared with high strain rate shear behavior from a modified split Hopkinson pressure bar (SHPB) technique. The experimental results indicate that the shear stiffness, failure stress, and failure strain are rate sensitive both in wale and course directions. The shear stiffness and failure stress increase with the the increase of strain rate. The failure strains along the wale and course directions decrease with increasing strain rate. Furthermore, the shear failure becomes more severe in the course direction than in the wale direction at high strain rates. The damage mode in the wale direction at various strain rates is punch shear failure, while that of the course direction is filament tow breakage and matrix cracks. The unique features of this article are to conduct the punch shear tests at high strain rates successfully using a modified SHPB apparatus for the novel 3-D knitted composite and find the strain rate sensitivity both in shear behavior and failure mode. The results will benefit the structural design of the 3-D knitted composite owing to the higher in-plane tension stiffness and strength of the composite than any other 3-D textile structural composites.

We study the generic mechanical behaviour of ceramic–ceramic nanocomposites inspired from biological materials. The nanocomposite models considered in our study are the regularly and stairwise staggered arrangements of stiff brittle platelets embedded in compliant brittle matrix. Molecular dynamics simulations are carried out to investigate the effect of strain rate on these nanocomposites. The variation in stress–strain behaviour and mechanical properties are analysed. The evolution of deformation processes is also investigated. Our results show the existence of different strain rate regimes separated by critical strain rate. Deformation mechanisms such as matrix cracking, crack bridging, interfacial debonding and hence platelet pullout are observed at lower strain rates. Amorphous deformation and direct debonding without matrix cracking are observed at higher strain rates.

Compressive response and microstructural evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite

In this paper, dynamic compression tests are developed to investigate the dynamic compression mechanical properties of the aluminum honeycomb structures at different strain rates, especially at the high strain rates. The difficulties at the high strain rates exist due to the large deformation, the low wave resistance and the size effect of the honeycomb structures. The Split Hopkinson Pressure Bar (SPHB) test method is carried out and special measures such as the adoption of waveform shaper, the size optimization of the impact bar and the specimen, and employment of the semiconductor strain gauge, etc. are taken to overcome the difficulties. It is discovered that the dynamic compression mechanical properties possess a stress hardening effect at a high strain rate from 1.3 × 103 s−1 to 2.0 × 103 s−1, but then a stress softening effect at a high strain rate of 4.6 × 103 s−1. It is also discovered that the yield strength and the average plateau stress at the strain rate of 2.0 × 103 s−1 is higher than that at the strain rate of 1.3 × 103 s−1. However, the yield strength and the average plateau stress at the strain rate of 4.6 × 103 s−1 is lower than that at the strain rate of 2.0 × 103 s−1 and 1.3 × 103 s−1, but higher than that at a quasi-static state. This indicates that the aluminum honeycomb structure is sensitive to the strain rate. Additionally, the damage mode of the aluminum honeycomb structure is plastic buckling, collapse and folding of the cell wall, which is carried out using dynamic compression tests. The folding length of the cell wall at a higher strain rate is found to be longer than that at a lower strain rate. The test results can also be used as the stress–strain curves of the honeycomb constitutive model at the high strain rates to carry out the numerical simulation of high-speed impact.

To study the dynamic compression and tensile mechanical behaviors of a bicomponent epoxy resin matrix composites, which were filled with a semi-crystalline thermoplastic Polyether-ether ketone (PAEK-C) resin, at high strain rate, the dynamic compression and tensile experiments were carried out on a modified split Hopkinson pressure bar (SHPB) and high speed material apparatus, respectively. Stress-strain curves of the epoxy resin matrix composites were obtained and analyzed. Damage mechanism under high strain rate was characterized through the scanning electron microscope (SEM) observation. Results of the dynamic compression tests indicated that, although the effects of strain rate remarkably influenced the variations in stress, the behaviors of the epoxy resin matrix played a more significant role than strain rate in the determination of the high strain rate. It was reflected through increased ductility of the samples and reduced slope of the stress-strain curves. The dynamic impact tensile tests results show that, PAEK-C fillers exhibited dramatic toughening effect. The increase of the volume fraction of PAEK-C rich phase inevitably forces the crack to overcome more tearing deformation of PAEK-C rich phase. At the same time, the enhancement of plastic capacity may also induce a larger range of cooperative deformation at the crack tip.

Hot tensile deformation and fracture behaviors of a typical ultrahigh strength steel

The aluminium-matrix composites (AMCs) consisted of (5, 10 and 15) x/% SiC particles (SiCp) in an aluminium alloy 7055 matrix. Specimens were taken from hot-press sintering. High-strain-rate tests were performed using the split-Hopkinson pressure bar (SHPB) method. The microstructures were observed with a scanning electron microscope (SEM) to understand the damage mechanisms of the SiCp/7055 Al composites at high strain rate. The SHPB test results show that the SiCp-reinforced composites are more sensitive to strain rate than the unreinforced material. The strain-rate sensitivity of the flow stress of these composites increases substantially with the increase of the strain rate. The flow stress of SiCp/7055Al composites with 10 x/% and 15 x/% SiCp at 3000 s–1 first increases and then decreases with the increase of the plastic strains, which was caused by the heat generated during adiabatic compression. Microstructure-characterization results show that SiCp cracking and SiCp/7055Al interface debonding are the main damage mechanisms of the composites. The SiCp volume fraction and strain rate affect the damage of composites during the dynamic compressive deformation of the SiCp /7055Al composites.

Tensile impact behaviors and damage mechanism of woven carbon fiber-reinforced-polymer laminates considering adiabatic shear band

High strain rate impact effect and failure behavior of 3D six-directional braided composites

Aluminum 6061 matrix composite reinforced by 35 wt% B4C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static (0.001 s−1) and dynamic (760–1150 s−1) compression experiments. The Johnson–Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson–Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.

In this study, pure titanium equivalent to Grade 1 was subjected to tensile tests at strain rates ranging from 10−6 to 100 s−1 to investigate the relationship between its mechanical properties and its twinning and slip. Deformation properties and microstructures of samples having average grain sizes of 210 μm (Ti-210), 30 μm (Ti-30), and 5 μm (Ti-5) were evaluated. With increasing strain rates, the 0.2% proof stress and ultimate tensile strength increased for all samples; the fracture strain increased for Ti-210, decreased for Ti-5, and changed negligibly for Ti-30. Comparing high (100 s−1) and low (10−6 s−1) strain rates, twinning occurred more frequently in Ti-30 and Ti-210 at high strain rates, but the frequency did not change in Ti-5. The frequency of 1st order pyramidal slip tended to be higher in Ti-30 and Ti-5 at low strain rates. The higher ductility exhibited by Ti-210 at high strain rates was attributed to the high frequency of twinning. In contrast, the higher ductility of Ti-5 at low strain rates was attributed to the activity of the 1st order pyramidal slip.

Effect of temperature and strain rate on quasi-static and dynamic compressive behavior of forged CrMnFeCoNi high entropy alloy