Structural integrity during remanufacture of a topologically interlocked material

Abstract

PurposeTopologically interlocked materials are a class of materials in which individual unit elements interact with each other through contact only. Cracks and other defects occurring due to external loading are contained in the individual unit elements. Thus, topologically interlocked materials are damage tolerant and provide high structural integrity. The purpose of this paper is to investigate the concepts of remanufacturing in the context of a material for which the intended use is structural such that the material's structural integrity is of concern. In particular, the study is concerned with the mechanical behavior of a topologically interlocked material.Design/methodology/approachA topologically interlocked material based on tetrahedron unit elements is investigated experimentally. Manufacturing with aid of a robotically controlled end‐effector is demonstrated, and mechanical properties are determined for a plate configuration. A conceptual mechanical model for failure of topologically interlocked materials is developed and used to interpret the experimental results.FindingsIt is demonstrated that remanufacturing of the topologically interlocked material is possible with only a limited loss of material performance. The proposed model predicts trends in agreement with the experimental findings.Research limitations/implicationsWhile the model predictions are qualitatively in agreement with experiments, more detailed finite element models are needed to predict the material performance accurately. Experiments were conducted on a model material obtained from a 3D printer and should be verified on other solids.Practical implicationsThe authors demonstrate that damage containment together with the absence of binders or adhesives enables reuse through remanufacturing without loss of structural integrity.Social implicationsTopologically interlocked materials emerge as attractive materials for sustainable engineering once their material performance are weighted with an environmental impact factor.Originality/valueRemanufacturing experiments on a novel class of materials were conducted and a new model for the characterization of the structural integrity of topologically interlocked materials is proposed and successfully evaluated against experiments in at least qualitative form.

Transverse loading of cellular topologically interlocked materials

“…The present model only considers elastic deformation in the unit elements. As shown in Mather et al (2012), and based on the estimates of strain, this assumption can indeed be violated. Assuming an ultimate stress for ABS of 50.00 MPa and consequently an ultimate strain of 0.03, the model presented would at least predict the peak loads well, but would overestimate the amount of deflection to failure.…”

“…Dyskin et al (2003a) expanded and generalized this concept, and introduced the term topologically interlocked materials (TIM) for this class of low-dimensional materials created from individual unit elements interacting with each other by contact and embedded within a constraining framework. It has been demonstrated that TIMs can possess attractive mechanical properties including: (i) high damage tolerance (Dyskin et al, 2003b;Khor, 2008;Schaare et al, 2008), (ii) negative stiffness characteristics under certain loading conditions (Estrin et al, 2011;Schaare et al, 2008), (iii) variable stiffness as adjusted by control of constraint (Brugger et al, 2009;Dyskin et al, 2003b), (iv) quasi-ductile response obtained from brittle constituent materials (Dyskin et al, 2001(Dyskin et al, , 2003a and (v) remanufacturability (Mather et al, 2012).…”

“…However, by employing a plate bending theory appropriate for a continuous solid, one does not account for the fact that no tensile stresses can be transmitted across the contact surfaces between the individual unit elements in a TIM. Also, a model for the characterization of the damage evolution in TIMs was developed in (Mather et al, 2012) by expanding previously developed models for prestressed mortar walls. This model explains the local conditions in the element-to-element contact, but fails to predict the overall characteristics of the TIMs.…”

Adaptive mechanical properties of topologically interlocking material systems

“…As adhesionless granular system, TIMs require an external constraint to provide resistance under the action of external load. TIM systems have already been shown to possess attractive mechanical properties including: (i) high damage tolerance ( [29]- [31]), (ii) negative stiffness characteristics under certain loading conditions ( [32], [33]), (iii) a quasi-ductile mechanical response response even if constituent materials are brittle ( [29], [34]- [36]), (iv) remanufacturability [37], and (v) advantageous dependence of stiffness, strength and toughness with variation in relative density if cellular unit elements are considered [38]. Past work has demonstrated the effect of change of the initial constraint conditions on the TIM system stiffness and load carrying capacity.…”

Mechanics of Multiscale Energy Dissipation in Topologically Interlocked Materials-11.1 STIR

“…Khandelwal et al [15] experimentally examined the quasi-static responses of TIMs asembled with regular tetrahedra, and proposed an analytic model to predicted the quasi-static beaviors of TIM with thrust line theory. Mather et al [16] studied the remanufacturability of TIMs, illustrated that only small portion of units could not be reused after failure of the TIMs. And for applications of TIMs, Estrin et al [17] proposed the potential application of TIM as protective tiles for the space shuttle.…”