Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core

Abstract

In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined and 3D confined) were employed in this paper. Up to seven impact–healing cycles were conducted. Macroscopic and microscopic damage–healing observation and analysis were implemented. Residual strength was evaluated using an anti-buckling compression test fixture. It was found that the healing efficiency was over 100% for almost all the impact–healing cycles; programming using 20% prestrain led to higher residual strength than that with 3% prestrain; 3D confined recovery resulted in higher residual strength than 2D confined recovery; and as the impact energy increased, the healing efficiency slightly decreased.

A viscoplastic theory of shape memory polymer fibres with application to self-healing materials

“…We have also demonstrated that this type of grid-stiffened SMP-based syntacticfoam-cored sandwich can inherently provide the required external confinement and facilitate the confined shape recovery for self-healing (John & Li 2010). Because of this, it is believed that grid-stiffened sandwich structures can be used in large structures such as plates or shells.…”

Thermomechanical behavior of thermoset shape memory polymer programmed by cold-compression: Testing and constitutive modeling

“…These advantages enable them to be active in various applications such as micro-biomedical components, aerospace deployable equipment and actuation devices (Tobushi et al, 1996;Liu et al, 2004;Yakacki et al, 2007). Lately, confined shape recovery of shape memory polymers has been used for repeatedly sealing/closing structural-length scale impact damages (Li and John, 2008;Nji and Li, 2010a;John and Li, 2010). Most recently, a biomimetic two-step self-healing scheme, close-then-heal (CTH), has been proposed by Li and Nettles (2010) and Xu and Li (2010), and further detailed by Li and Uppu (2010), for healing structural-length scale damage autonomously, repeatedly, and molecularly.…”

A Kirigami shape memory polymer honeycomb concept for deployment

“…The polymer can then be 'taught' a temporary shape by thermoforming above its T g , and it can be returned to its permanent shape again by heating above its transition temperature. SMPs are currently developed for a wide variety of applications, from general morphing structures [32], selfhealing [33], smart mandrels [34], 3D printing [35] to damping [36] and viscoelastic/reversible adhesion [16].…”