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In order to correctly understand the mechanical behavior, damage mode and damage mechanism of AlSi10Mg optimized structure under compressive load, a series of experimental and simulation studies were carried out. The stress-strain response, bearing capacity, energy absorption characteristics, damage mode and mechanism of the structure are analyzed and discussed. The results show that AlSi10Mg porous structure has obvious strain hardening effect, but no obvious strain rate effect. The volume fraction of AlSi10Mg porous structure increased from 9.43% to 22.15%, and its bearing strength increased from 22.34 MPa to 50.98 MPa. The optimized design structure is complex in this paper, which eliminates undesirable failure modes, and the benefit of high specific energy absorption is retained. The experimental and simulation results show that shear failure is the main cause of structural damage, and the normal of the failure section and the load action direction are roughly inclined at an angle of 45° ∼ 55°. The research results can provide an important reference for the optimal design of porous metal structure.

Rate-dependent mechanical response of fly ash cenospheres polyurethane syntactic foams (CPSFs) with hierarchical cell structure was examined through dynamic compression tests. Quasi-static compression strength and specific energy absorption varied in the range of 9.5–29.5 MPa and 4.8–13.0 MJ/m3 within the density of 0.5–0.7 g/cm3. The thermal conductivity coefficient of CPSFs increased from 0.08 W/m/K to 0.13 W/m/K with density, while the specific heat capacity varied in a narrow range of 0.9–1.07 J/g/K. At high strain rates the strength and plateau stress of CPSFs with density of 0.6 g/cm3 increased 25%–39% and 13%–43%. The proposed foam is comparative potential in civil engineering according to its thermal insulation performance and excellent shock dissipation properties. Due to complicated microstructure, CPSFs exhibited different strain rate sensitive behaviors in the initial collapse stage and the stable collapse stage. A constitutive relation was developed to describe dynamic stress-strain response which includes the elastic stage, the initial collapse stage characterized by nonlinear stress increasing and decreasing process, the platform stage and the densification stage. The predictions shown good accordance with the experimental results in wide strain rate range.

The Al2O3/SiC composite has an improved mechanical property compared with alumina matrix, and it can be used in the lightweight armour system. In this study, the dynamic tensile and compressive strength, strain rate sensitivity, fracture mechanism and fragments scale of the composite were carried out by experimental and theoretical analysis. Results showed that the dynamic strength of the Al2O3/SiC composite was sensitive to the strain rate, and it was controlled by its microstructure. The microfracture mechanism of the composite varied with the locations and stress states of specimen, which consisted of second phase particles effects, the intergranular and transcrystalline fracture mode, fractured core area, grain-boundary crack, grain distortion and splitting, cleavage fracture zones, slip bands et al. In the dynamic compression experiments, the statistic analysis results of recycled fragments were more agreed with the prediction of the modified DID model.

Low-velocity impact responses of typical hollow brittle particles (HBPs) were tested with a strain-limited loading technique to investigate the particle breakage characteristics at both macro and particle levels. The quasi-static compressions were also conducted for comparison. Effects of strain rate and particle size distribution on the stress-strain response, particle breakage and macro deformation behaviors were discussed. Results show that the strength, plateau stress and energy dissipation of hollow brittle particles all exhibited significant strain rate sensitivity. The particle size gradations after single-impact compression were obtained through the laser diffraction technique. Quantitative analysis on the fragmentations and the Hardin relative breakage shown that the dynamic breakage ratio and the breakage extent of the hollow particles at the same strain were larger than that under quasi-static compressions. Moreover, it was found that the Hardin relative breakage generated by specific energy dissipation decreased with the strain rate. The reduction of fracture energy dissipation efficiency and the rate-dependent breakage response of particle breakage are the intrinsic reasons for bulk-scale strain rate effects of HBPs. Finally, the macro deformation behaviors of hollow brittle particles were analyzed through digital image correlation (DIC) technique. It was observed that there exists a competition mechanism between the boundary effect and the inertial effect in dominating the compression patterns. The deformation mechanism was sensitive to the loading velocity.

Multi-scale high energy insensitive particle reinforced composites (MSHEIPRC) are the most important part of the anti-missile sandwich wall structure. Its dynamic mechanical behavior and damage mode will directly affect the success of anti-missile capability. In this paper, based on a modified Split Hopkinson Pressure Bar (SHPB) experimental technique and the design of triaxial impact loading test device, combining with theoretical study and meso analysis, the dynamic mechanical response under high strain rates and damage characteristics of MSHEIPRC under high overload were carried out. The results show that the dynamic stress-strain curves of MSHEIPRC are highly non-linear and have obvious strain rate effect and density effect. Compared with the experimental results, the modified constitutive model can accurately describe its dynamic mechanical behavior at high strain rates. Based on the energy model and related parameters, the bond strength between the surface of crystal particles and the binder is calculated to be about 0.6 MPa. Therefore, the shear debonding damage mode between the surface of crystal particles and the binder is first found at the stage of small impact loading. The critical fracture strength of cracks with different sizes is calculated by Griffith method. With the increase of impact loading pressure, the fracture phenomenon gradually appeared on the surface of crystal particles, which was basically consistent with the theory model. Continuing to increase the impact loading pressure, sufficient shock wave energy forces crystal particles to produce transgranular fracture, which leads to crystal particles breaking.