Study of layer orientation on the fracture behavior of two additively manufactured thermoset resins, A

This work examines the fracture behavior of additively manufactured (AM) thermosetting resins to enable rapid production of lightweight and functional polymeric and composite materials that can meet a wide range of applications. Specifically, the role of print orientation on the quasi-static and dynamic fracture response of two distinct AM polymer materials, DA-3 and PM-EM828, is presented. While predictive simulations often leverage quasi-static fracture criterion, impulsively loaded cracks can have substantially different resistance to growth. To study dynamic fracture, a unique long-bar apparatus is used to fire a striker at the opposite end of notched and pre-cracked specimens to create a dominantly dynamic Mode-I (opening) load. Digital Image Correlation (DIC) is used in conjunction with ultra-high-speed imaging to capture the evolving displacement fields ahead of the crack tip. The elastodynamic solution for a stationary crack is optimized using a least square fit to extract the evolving critical stress intensity factor (SIF) leading to fracture initiation. These results are compared to quasi-static experiments of the same material and similar geometries on a standard load frame. Findings suggest that the print orientation does slightly affect the quasi-static and dynamic fracture response of DA-3, however the PM-EM828 does not show statistically significant orientation dependencies on fracture behavior. The DA-3 exhibited between 46% to 60% higher quasi-static fracture toughness values than dynamic, on average, but the trends mirrored the printed orientation dependency of dynamic loading. Conversely, PM-EM828 exhibited approximately 20% lower quasi-static fracture values than dynamic values and had little to no orientation dependency. The overall toughness of the PM-EM828 layers are on a similar level to their interlayer adhesion zones, suggesting why there may be little print orientation dependence. Conversely, the DA-3 layers are less brittle than their interlayer adhesion zones, and so the orientation of the adhesion zones with respect to the print orientation seems to allow for a greater resistance to fracture.

Name thesis:degree_name

Master of Science (M.S.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

Colorado School of Mines. Arthur Lakes Library

Year dc:date.issued

2021

Author dc:creator

• Brunstad, Nicholas John

Advisor dc:contributor.advisor

• Lamberson, Leslie

Committee members dc:contributor.committeemember

• Berger, John R.
• Eliasson, Veronica
• Koumlis, Stylianos

• digital light processing
• fracture mechanics
• quasi-static fracture
• dynamic fracture
• additive manufacturing
• print orientation

Statement dc:rights

• Copyright of the original work is retained by the author.

Language dc:language.iso

eng, English

Identifier

T 9090

OAI identifier oai:identifier

oai:repository.mines.edu:11124/176403