Simulated and Experimental Investigation of Mechanical Properties for Improving Isotropic Fracture Strength of 3D-Printed Capsules.

Taeuk Lim,Hao Cheng,Jasung Lee,Wonsuk Jung,Sunghoon Kim,Wonil Song

doi:10.3390/ma14164677

Taeuk Lim, Hao Cheng + Show 4 more

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https://doi.org/10.3390/ma14164677

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Abstract

Three-dimensional (3D) printer-based self-healing capsules, embedded in cement composites, were proposed to heal cracks, as they allow for various structural designs of capsules, repeatable fabrication, and strength analysis. Out of many 3D printing methods, such as fusion deposition modeling (FDM), powder layer fusion, and PolyJet printing, FDM was used to design, analyze, and produce new self-healing capsules, which are widely used due to their high-speed, low-cost, and precise manufacturing. However, the PLA extruded in the FDM had low adhesion energy between stacked layers, which caused a degradation of the performance of the self-healing capsule, because it had different strengths depending on the angle between the stacked layers and the applied load within the concrete structure. Therefore, in this paper, specimens were produced, in accordance with ASTM specifications, using the FDM PLA method, and mechanical properties were obtained through tensile, shear, and compression tests. Additionally, the isotropic fracture characteristics of the four types of capsules were analyzed through finite element method analysis. Subsequently, the 3D-printed capsules were produced, and the fracture strength was analyzed in the x, y and z directions of the applied load through a compression test. As a result, the newly proposed capsule design was verified to have an isotropic fracture strength value of 1400% in all directions compared to conventional spherical thin film capsules

Highlights

There has been increased research interest in the use of self-healing capsules to enhance the safety of concrete structures in terms issues related to cracks [1,2,3,4]
Most capsules rely on chemical manufacturing methods or flow control processes [25]
The vulnerable areas of each specimen were investigated by analyzing the fracture The vulnerable areas of each specimen were investigated by analyzing the fracture location and strength of the fusion deposition modeling (FDM)-based PolyLactic Acid (PLA) specimens

Summary

Introduction

There has been increased research interest in the use of self-healing capsules to enhance the safety of concrete structures in terms issues related to cracks [1,2,3,4]. Glass capsules [5,6] and glass cylinders [7,8,9,10] were widely used to encapsulate healing agents [11,12,13], but the disadvantage is that additional structures are needed for protection because glass capsules cannot withstand the concrete mixing process in the form of a cement paste or a metallic wire [14]. In the case of capsules manufactured using the flow control process, when the size is greater than the order of micrometers, the buoyancy makes it difficult to precisely manufacture the capsules [26]

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