The Woodruff School

SUMMARY

Additive Manufacturing, also known as 3D printing, is an emerging technology that has revolutionized product realization. Like any other manufacturing process, the properties of manufactured parts or materials are affected by the additive manufacturing process. One class of polymers widely used in additive manufacturing is Ultraviolet (UV)-curable photopolymers. Photopolymers are light sensitive thermoset polymeric materials and transform their phase from liquid to solid state when exposed to UV light or Laser. Photopolymers provide lower viscosity for easier printing process and fast curing reactions, which are suitable for 3D printing of energetic materials. To pave the way for 3D printing of energetic materials, it is necessary to understand the mesoscale mechanisms responsible for the behavior of additive manufactured (AM) materials subjected to dynamic loading. Dynamic loading events can cause severe damage and energy dissipation leading to formation of temperature spikes (hotspots), resulting in thermal softening, thermal runaway, or even the onset of chemical reactions in energetic materials. Hotspots occur due to several dissipation mechanisms, including viscoplasticity, viscoelasticity, void collapse and internal friction along crack surfaces.

To understand the mechanisms responsible for the behavior of additive manufactured materials subjected to dynamic loading and to validate models, it is important to experimentally measure the deformation and temperature fields at the microstructure level. This work proposes the development of an experimental capability that captures simultaneous time- and space-resolved recording of deformation and temperature with an unprecedented level. Since experiments do not allow full understanding and detailed quantification of the underlying mechanisms primarily due to the lack of abilities to directly measure, Lagrangian cohesive finite element (CFEM) simulations will also be performed. The CFEM simulations will provide a unique opportunity to analyze the effects of printing patterns and initial defects. By better understanding of the thermo-mechanical response of additive manufactured materials, these materials can be custom designed and tailored for specific purposes using the geometric ﬂexibility offered by additive manufacturing.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Amirreza Keyhani

TIME:	Friday, May 3, 2019, 11:15 a.m.

PLACE:	MRDC Building, 4211

TITLE:	Dynamic Thermo-Mechanical Response of Additive Manufactured Materials

COMMITTEE:	Dr. Min Zhou, Chair (ME) Dr. Richard Neu (ME) Dr. Antonia Antoniou (ME) Dr. Shuman Xia (ME) Dr. Julian J. Rimoli (AE)

SUMMARY Additive Manufacturing, also known as 3D printing, is an emerging technology that has revolutionized product realization. Like any other manufacturing process, the properties of manufactured parts or materials are affected by the additive manufacturing process. One class of polymers widely used in additive manufacturing is Ultraviolet (UV)-curable photopolymers. Photopolymers are light sensitive thermoset polymeric materials and transform their phase from liquid to solid state when exposed to UV light or Laser. Photopolymers provide lower viscosity for easier printing process and fast curing reactions, which are suitable for 3D printing of energetic materials. To pave the way for 3D printing of energetic materials, it is necessary to understand the mesoscale mechanisms responsible for the behavior of additive manufactured (AM) materials subjected to dynamic loading. Dynamic loading events can cause severe damage and energy dissipation leading to formation of temperature spikes (hotspots), resulting in thermal softening, thermal runaway, or even the onset of chemical reactions in energetic materials. Hotspots occur due to several dissipation mechanisms, including viscoplasticity, viscoelasticity, void collapse and internal friction along crack surfaces. To understand the mechanisms responsible for the behavior of additive manufactured materials subjected to dynamic loading and to validate models, it is important to experimentally measure the deformation and temperature fields at the microstructure level. This work proposes the development of an experimental capability that captures simultaneous time- and space-resolved recording of deformation and temperature with an unprecedented level. Since experiments do not allow full understanding and detailed quantification of the underlying mechanisms primarily due to the lack of abilities to directly measure, Lagrangian cohesive finite element (CFEM) simulations will also be performed. The CFEM simulations will provide a unique opportunity to analyze the effects of printing patterns and initial defects. By better understanding of the thermo-mechanical response of additive manufactured materials, these materials can be custom designed and tailored for specific purposes using the geometric ﬂexibility offered by additive manufacturing.