Faculty of Engineering

Permanent URI for this community

https://scholar.sun.ac.za/handle/10019.1/10

The Faculty of Engineering at Stellenbosch University is one of South Africa's major producers of top quality engineers. Established in 1944, it currently has five Engineering Departments.

News

For the latest news click here.

Browse

Browsing Faculty of Engineering by Subject "3D Printing -- Concrete"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Experimental and computational mechanics for the constitutive modelling of extrusion-based 3D concrete printing
    (Stellenbosch : Stellenbosch University, 2021-12) Van den Heever, Marchant; Van Zijl, Gideon P. A. G.; Kruger, Jacques; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: The structural use of 3D concrete printing (3DCP) has globally gained traction owing to the host of benefits permitted by an industrialised manufacturing style approach to construction. However, due to the novelty of this technology, no standardised hardened-state mechanical characterisation or design specifications have been established. Moreover, limited research has been conducted on the non-linear hardened-state finite element (FE) analysis of 3DCP components. Therefore, this research proposes mechanical testing protocols, computational modelling strategies and advanced microstructural characterisation procedures to evaluate the fundamental failure mechanisms in 3D printed concrete (3DPC) to provide critical insights into the design and analysis of 3DCP components or structures. Novel hardened-state material characterisation procedures are proposed, which elucidate the anisotropic strength and deformation attributes of 3DCP components and provide the necessary material and model parameters for FE simulation. An analogy between the well-established computational modelling strategies for masonry structures and 3DCP is drawn. Two anisotropic non-linear simulation strategies are adapted and introduced for application in the 3DCP design space. Both techniques are novel within the context of 3DCP and provide accurate results of the experimentally attained capacity and cracking patterns of the members. The constitutive models of the proposed simulation strategies are studied and found to overestimate the shear capacity of interfacial regions due to the assumption of a Mohr-Coulomb failure criterion. To further advance the current knowledge basis, the microstructural morphology is comprehensively characterised via X-ray computed tomography and deemed a potential contributor to the reduced strength and stiffness portrayed by 3DCP specimens. Subsequently, it is demonstrated how the microstructure and orientation of the axes of the composite material influence the direction of crack propagation, validating that porosity content and pore geometric attributes have distinct but complementary effects on the mechanical capacity of 3DPC. It is then revealed why anisotropy is so prevalent in 3DCP and why the shear strength of interfacial regions is overestimated. Thereafter, it is divulged how to improve predictions of the non-linear shear constitutive behaviour computationally through a novel modified Mohr-Griffith yield criterion. Solid theoretical descriptions relate the microstructural morphology to damage mechanisms and the resulting anisotropic shear strength in mould-cast and 3DCP elements. Employing the enriched understanding of the mechanical performance of 3DPC's, potential remedies to alleviate the anisotropic response in 3DCP components are proposed. In essence, this research demonstrates how synergies between the experimental and computational mechanics and advanced microstructural characterisation techniques permit improved constitutive modelling for 3DCP. Finally, it is recommended how the knowledge gained from this dissertation can be utilised to take an incremental step towards the detailed design and analysis of 3DCP structures.