Abstract
Hollow sphere structures with perforations (PHSSs) in three different arrangements (simple cubic (SC), body-centred cubic (BCC), and face-centred cubic (FCC)) were fabricated through three-dimensional (3D) printing, and the mechanical behaviours of these PHSSs under quasi-static compression were investigated experimentally and numerically. The results indicated that under uniaxial compression, the PHSSs mainly undergo three stages, i.e., a linear elastic stage, a large deformation or plateau stage, and a densification stage. During the stage of large deformation, the SC and BCC PHSSs experience a preliminary compaction sub-stage after layer-by-layer buckling, while for the FCC PHSS, layer-by-layer collapse and compaction are the dominant deformation behaviours. A numerical simulation was employed to study the mechanical properties of PHSSs with different geometric parameters under quasi-static compression and to explore the effect of the wall thickness, hole diameter, and sphere arrangement on the first peak stress, plateau stress, and specific energy absorption (SEA) of the PHSSs. The results reveal that the geometric parameters have a significant impact on the large deformation behaviour and energy absorption capacity of PHSSs. The presented PHSS is also proven to be much lighter than traditional metallic hollow sphere structure (MHSS) and has higher specific strength and SEA.
Highlights
Published: 2 July 2021With abundant pores in the matrix material and an internal microstructure, cellular metal or metal foam has unique functional and structural properties
A metallic hollow sphere structure (MHSS) is a high-quality cellular material that is usually manufactured by filling thin-walled hollow spheres into a polymer matrix, sintering the spheres by applying heat and pressure and bonding spheres using a liquid phase [2]
With ping-pong balls as the experimental object, Yu et al carried out a series of static and dynamic compression experiments on single-ball and multi-ball arrays, theoretically derived the compressive deformation pattern of a stacking of spheres, and verified the theories through various two-dimensional (2D) ping-pong ball stackings; some findings were beneficial to understanding the deformation mechanism of a real MHSS [17,18,19]
Summary
With abundant pores in the matrix material and an internal microstructure, cellular metal or metal foam has unique functional and structural properties. With ping-pong balls as the experimental object, Yu et al carried out a series of static and dynamic compression experiments on single-ball and multi-ball arrays, theoretically derived the compressive deformation pattern of a stacking of spheres, and verified the theories through various two-dimensional (2D) ping-pong ball stackings; some findings were beneficial to understanding the deformation mechanism of a real MHSS [17,18,19] They conducted experimental studies through quasi-static tests and dynamic tests to investigate the large deformation behaviour of sintered MHSSs, and a long plateau length (up to 67% of the nominal strain) and localisation of deformation were observed [20]. Some understanding of the static and dynamic mechanical properties of hollow sphere structures/materials has been gained through these studies, which were mostly conducted under ideal stacking and connection conditions by using the finite element method, the obtained theoretical formulas are not consistent with the experimental results in some cases. The effect of geometric parameters, such as wall thickness, hole diameter and packing pattern, on the structural deformation mode, first peak stress, plateau stress and specific energy absorption (SEA) was analysed by using the finite element method, which offers a reference for further lightweight engineering applications of 3D printed hollow sphere structures
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