Bilayer Glass Foams with Tunable Energy Absorption via Localized Void Clusters

Abstract

The research in this article entails the design of materials systems and tunable energy absorbing properties respond to a range of energy absorption needs in different impact conditions. Tunable energy absorption of bilayer cellular foams is investigated using hollow glass spheres with different wall thickness and densities. Co‐cured bilayer foams are prepared through sintering of the spheres, and their microstructures and mechanical responses to quasistatic uniaxial compression are investigated. Co‐cured system exploits localized voids density (>50 μm) locally at the interface which is induced via different shrinkage rate of spheres, leveraging tunable energy absorptions. Mechanical testing shows that the voids at the interface lead in the sequential collapse of the layers, resulting in a distinctive two‐step stress–strain profile. For comparison, bilayer samples are fabricated using epoxy. These samples show a different mechanical response from the co‐cured sample by not showing the two‐step stress–strain. The co‐cured samples exhibit 14.8% more specific energy absorption than epoxy bonded samples. The results suggest that co‐cured samples can limit impact stress and achieve a higher energy absorption capacity than epoxy bonded samples. The manufacturing concept and system design expand the capabilities of cellular foams, yielding desired energy absorbing properties in a diverse range of applications.

Tunable Energy Absorbing Property of Bilayer Amorphous Glass Foam via Dry Powder Printing

“…Recently, sintered glass foam with density gradients has exhibited progressive structural collapse during crush to demonstrate tunable energy absorption [5,[19][20][21][22][23][24]. We previously showed the potential tunability of the glass foam via forming a bilayer structure that eventually controls the shape of the stress-strain curves in a certain level [24]. In this paper, we further demonstrate such tunability by employing layered foam structures utilizing different layer-wise foam densities.…”

“…The void cluster in the interfacial region leads to initial compression in GF3 layer first, followed by compression of GF4 layer. A more in-depth study on the interfacial void cluster of bilayers was published previously [24]. In the GF1/GF4 system, the foams have a large difference in their densities, so the effect of the interfacial void cluster is less significant.…”

“…Graded porous structures and syntactic foams are fabricated via gluing multi-layers or blowing agents. Recently, sintered glass foam with density gradients has exhibited progressive structural collapse during crush to demonstrate tunable energy absorption [5,[19][20][21][22][23][24]. We previously showed the potential tunability of the glass foam via forming a bilayer structure that eventually controls the shape of the stress-strain curves in a certain level [24].…”

“…They are popularly used in syntactic foam which is a cellular polymeric matrix filled with hollow microspheres [30][31][32]. Recently, a cellular structure was successfully fabricated by sintering hollow glass microspheres [12,24,[33][34][35][36]. A key advantage of HGM-based foams is that the cellular solid exhibits thermal stability up to 600 °C, which usually cannot be achieved with syntactic foam due to polymeric binders or matrices.…”