Preparation of glass microspheres/aluminum matrix syntactic foam and its quasi-static compressive characteristic and energy absorption

Aluminum matrix syntactic foams are a novel class of cellular materials synthesized by hollow particles and aluminum matrix, which exhibit lightweight and high energy-absorbing capacity. In this study, the glass microspheres/aluminum matrix syntactic foams were prepared by the spark plasma sintering (SPS) method. The effects of the content and size of microspheres on the quasi-static compressive deformation behavior and energy absorption properties of the syntactic foams were analyzed by optical microscope (OM), SEM, quasi-static compression in situ observation, and digital image correlation (DIC) characterization. The results show that the microspheres of aluminum matrix syntactic foams prepared by two-step heating SPS sintering are uniformly embedded in the aluminum matrix, while the aluminum matrix is completely fused with high densification. With the increase of the microsphere content, the compressive stress of the syntactic foam decreases as a whole, meanwhile, the yield plateau expands and changes from smooth to zigzag. In addition, the compressive deformation behavior gradually develops from a relatively uniform drum-shaped deformation to brittle shear. The energy absorption capacity of the syntactic foam with the volume fraction of 50vol% is 23.6 J·cm⁻³, which is higher than that with the volume fraction of 30vol% and 70vol%. There is an optimal correspondence between the energy absorption capacity and the microsphere content of the syntactic foam. Small-sized microspheres have better compressive resistance. With the increase of the small-sized microsphere proportion, the syntactic foams can withstand higher stress and strain concentration on the microscopic level, as a result, the compressive strain of shear deformation increases on the macro level. In this study, the peak stress and energy absorption capacity of the syntactic foam with small-sized microspheres are 89.4 MPa and 29.0 J·cm⁻³, which are 23.5% and 22.9% higher than those of the syntactic foam with large-sized microsphere, respectively.