Effects of Print Geometry Alterations and Layer Staggering on the Mechanical Properties of Plain and Fiber-Reinforced 3D Printed Concrete
Presented By: Avinaya Tripathi
Affiliation: Arizona State University
Description: Conventional approaches to concrete 3D printing relies on printing concrete in a straight (linear) print path, with layers overlaid on top of each other. This results in inter-layer and inter-filament joints being potential weak spots that compromise the mechanical performance. This paper evaluates simple alterations to the print geometry to mitigate some of these effects. A printable mixture with 30% of limestone powder replacing cement (by mass), with a 28-day compressive strength of about 70 MPa in the strongest direction, is used. S- and 3-shaped print paths are evaluated as alternatives to the linear print path. Staggering of the layers ensures that the inter-filament joints do not lie on the same plane along the depth. Flexural strength enhancement is observed when print geometries are changed and/or layers are staggered. The study shows that print geometry modifications mitigate mechanical property reductions attributed to inter-filament defects in concrete 3D printing.
Parametric Study on Investigating Fracture Characteristics of 3D-Printed Concrete
Presented By: Reza Sedghi
Affiliation: University of New Mexico
Description: The popularity of 3D-printed concrete technology is increasing because of its fast, cost-effective construction, as well as its flexible geometric and automated capabilities. This technology reveals unique performance characteristics, especially in terms of anisotropy, which are not commonly found in traditional cast-in-place concrete elements. This study employs a three-point bending test to explore the fracture behavior of 3D-printed concrete. So, the flexural strength and the fracture energy are systematically investigated, considering variations in notch length to beam depth ratio, printing direction (parallel and perpendicular), and filament angle. The study also employs Digital Image Correlation (DIC) to analyze crack patterns and movement until complete specimen failure.
Mechanical Behavior of 3D-Printed High-Ductility High-Strength Cementitious Materials
Presented By: Mo Li
Affiliation: University Of California, Irvine
Description: This study focuses on the mechanical behavior of new 3D-printed strain-hardening cementitious materials that integrates ultra-high tensile ductility with high compressive strength. The characterized mechanical properties include compressive, tensile and flexural properties. The effects of printing path and loading directions on these properties as well as damage pattern are also studied. The new 3D-printed cementitious materials can potentially reduce the need for steel reinforcements in 3D-printed concrete structures.
Tough Cementitious Mortar-Silicone Multi-Material Composite Enabled by Automated Multi-Material Additive Manufacturing Process
Presented By: Aimane Najmeddine
Affiliation: Princeton University
Description: Cementitious materials remain susceptible to damage and cracking and suffer from low fracture toughness. This presentation provides a thorough experimental, analytical, and numerical examination of the mechanical properties of cementitious mortar-silicone multi-material composites, a development made possible by advancements in automated additive manufacturing processes. The research is enabled by the development of a new multi-material additive manufacturing (MMAM) platform that facilitates the sequential and/or simultaneous deposition of multi-material assemblies with diverse architectures. Inspired by the toughening mechanism found in natural systems such as Nacre, the enhancements in fracture toughness and strength of these composites were examined compared to traditional, monolithic cement structures. It is hypothesized that the presence of soft interlayers can promote the spread of damage. Notched and un-notched experiments (SENB and 3PB tests) were conducted on 3D-printed beams comprised of alternating layers of mortar and silicone to characterize the composite behavior under bending and Mode-I. Our recently developed phase-field cohesive zone crack propagation model for hard-soft architected materials was used to simulate the role of materials and geometric variables on mechanical response. LEFM was used to compare the simulation with theoretical benchmarks. The significantly enhanced fracture toughness is attributed to several new toughening mechanisms that were corroborated experimentally and numerically, owing to their hard-soft material interaction, and crack dissipation events such as crack deflection, crack propagation, and crack bridging. By numerically varying sample architecture (e.g., soft layer thickness) and material constitutive properties (e.g., different soft materials), a more thorough understanding of the various toughening mechanisms can be achieved for such multi-materials. New design principles can be extended to other hard-soft and har
Developing Engineered Polymeric Reinforced Cementitious Composite (EPRC) Using Mechanics of Materials Principles and Nature-Inspired Hollow Architectures
Presented By: Yaghoob Amir Farnam
Affiliation: Drexel University
Description: This research investigates the incorporation of nature-inspired architectural elements into Mechanics of Materials (MoM)-based reinforcement layouts for reinforced cementitious composites (RCs). In contrast to conventional MoM layouts that prioritize longitudinal rebars for tensile strength, this study focuses on enhancing the flexural properties of RCs by integrating nature-inspired features such as hollow tubes observed in plant stems. The investigation employs both experimental and numerical approaches to assess the flexural performance of engineered polymeric reinforced cementitious composites (EPRCs) featuring integrated nature-inspired hollow motifs. The findings reveal that the collaborative integration of nature-inspired hollow architecture into the MoM-based design significantly enhances modulus of rupture, toughness, and ductility compared to traditional MoM-based layouts. This improvement is attributed to an increased area moment of inertia and enhanced bond between reinforcement and matrix. The study offers valuable insights for optimizing the mechanical characteristics of RCs in civil engineering applications through the inclusion of nature-inspired architectural designs.
Sinusoidal Helicoidal Architecture with Nonplanar Layering of Filaments in Additively Manufactured Cementitious Materials
Presented By: Yu Wang
Affiliation: Purdue University - West Lafayette
Description: The adoption of additive manufacturing of cementitious materials empowered the flexible shaping of external forms and the internal architecture of structural elements. The application of internal filament architectures enables the production of structural elements with unique and tailorable mechanical properties. An effective strategy for designing architectured cement-based materials involves drawing inspiration from nature, particularly biological composites celebrated for their exceptional attributes of high impact resistance and damage tolerance. The sinusoidal helicoidal architecture found in the dactyl club of the mantis shrimp stands out as a notable example of bio-inspired design. During predatory interactions, the impact region of the mantis shrimp's dactyl club, equipped with a unique sinusoidal helicoidal architecture, demonstrated exceptional resistance to extremely high compressive stresses, effectively withstanding the intense forces generated during shell-breaking actions. This presentation will cover the development of 3D-printed concrete (3DCP) specimens featuring nonplanar layering of filaments and sinusoidal helicoidal architectures aimed at improving the mechanical performance of 3DP concrete under compressive loading. The approach to developing the nonplanar layering of filaments in 3D printed concrete will be highlighted, and the influence of this novel architecture on selected mechanical properties of 3D-printed concrete specimens will be discussed.