MECHANICS OF QUASI-BRITTLE MATERIALS
MATTHEW TROEMNER, E.I., S.M.ASCE
PhD Student of Civil Engineering
Northwestern University
Personal Website Web of Science ResearcherID: AAA-9260-2019
Google Scholar ORCID: 0000-0002-3338-6013
ACI Convention 2019: Matthew Troemner, Madura Pathirage, Dr. Gianluca Cusatis, Dr. Roman Wan-Wendner, and Dr. Gianluca Ranzi
Overview
I am a PhD candidate of Civil Engineering within the Mechanics of Quasi-Brittle Materials Research Group at Northwestern University. I received a Master of Engineering in Structural Engineering and a Bachelor of Science in Architectural Engineering from the Illinois Institute of Technology.
My current research includes development of high fidelity meshes and models for concrete at the meso- and micro-scale, and additive construction of concrete and quasi-brittle materials. In my free time I enjoy photography, video editing, traveling, and downhill skiing.
Current Research
A Multiphase Lattice Discrete Particle Model for Miniscale Simulation of Mortars and Concretes
At the mortar scale, also called concrete miniscale, concrete can be regarded as a three-phase composite composed of (1) a porous matrix, the cement paste; (2) aggregate particles of all size (from several microns to few centimeters in standard concrete); and (3) a thin layer (size of several microns) of material at the interface between cement paste and aggregate pieces, the so called Interfacial Transition Zone (ITZ), which has distinctly different properties compared to the cement paste bulk.
An updated formulation of the Lattice-Discrete Particle Model is under development to capture the distinct behavior of these three phases. Additionally, it is desired to to use such a model to predict the global behavior of a concrete using only properties of the underlying constituents.
Marscrete, a Martian Concrete for Additive Construction Applications Utilizing In Situ Resources
For humans to thrive on Mars for any extended period, semi-permanent structures will have to be erected. Such a large and robust habitat would be impractical to transport prefabricated, thus utilization of local geo-environmental resources is desired. This study is on recent research performed towards the formulation and characterization of a Martian infrastructure material, called Marscrete.
Marscrete is composed, in its simplest version, by sulfur and Martian regolith with a 50-50 mass ratio. Sulfur is plentiful in compounds on and below the surface of Mars, and regolith is a ubiquitous material. While a generically suitable construction material, Marscrete, when modified with mission-recycled polyethylene fibers, also demonstrates high capabilities for 3D-printing applications – a likely automated construction technique of Martian structures.
Design and Analysis of 3D-Printable Thin-Shell Dome Structures for Extraterrestrial Habitation
Extreme environmental conditions, unusual loadings and, most importantly, the availability of novel construction techniques will likely dictate the form of any extraterrestrial habitat built on Mars. While a habitat could be constructed by astronauts, it is highly preferred for such a structure to already exist when the first humans land on the Martian surface. Thus, automated structure fabrication, equipped with 3D-printing technologies that use in situ resources is an intriguing approach to consider.
This research is on the design and analysis of a dome-shaped Martian habitat as part of NASA’s 3D-Printed Habitat Challenge. The structure has a novel composite hemispheric-parabolic dome that is optimized to sustain self-weight and environmental loads, and to be 3D-printed on an inflatable pressure vessel with Marscrete, a Martian concrete manufactured primarily with local Martian regolith and sulfur.
Large-Scale 3D-Printing of Infrastructure Materials and Sulfur Concretes
The Northwestern Multi-scale 3D Printing Infrastructure Laboratory was developed for cross-discipline research into large-scale 3D-printing, including systems controls, material development, and printing/extrusion equipment. Matthew currently leads the research in these areas within the Quasi-Brittle Materials Research Group.
The defining feature of this facility is an ABB industrial robot that has been adapted with a variable temperature melt extruder to produce sulfur-based concretes for both Earth and Mars constructions. Due to the open nature of the extruder, the robot is also capable of printing with various other temperature-dependent composites. Additionally (as shown in the video), printing using mortars and cementitous materials is also capable, and research in this area is underway.
Embedded Beam and Discrete Lattice Models for Simulation of Fiber-Reinforced Composite Laminates
Two distinct formulations of models for simulation of fiber-reinforced unidirectional composite laminates is underway. These formulations are being developed for comparison of limitations for simulating such materials, as well as comparison with their more traditional continuum- and FEM-based counterparts.
Examination Of Size Effect In Shear Walls Using Lattice-Discrete Particle Modeling
Size effect is a phenomena where the nominal strength of a system differs between two geometrically similar structures composed of the same material. This study includes the simulation of a variety of squat reinforced concrete shear walls subjected to assorted loads. Simulations will be performed on a selection of scaled walls to better understand size effect in such structures.
Data for comparison and calibration has been pulled from large-scale experiments of the exact walls under examination.
Lattice-Discrete Particle Model-Based Analysis Of Quasi-Brittle Materials
Additional research is always ongoing on more traditional concretes using the Lattice-Discrete Particle Model (LDPM). LDPM simulates concrete at the mesoscale - the length scale of aggregates.