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Study on Flexural Properties of Polyamide 12 according to Temperature produced by Selective Laser Sintering

선택적 레이저 소결 제작 폴리아미드 12 시편의 온도별 굴곡 특성 연구

  • Kim, Moosun (Urban Transit Research Team, Korea Railroad Research Institute)
  • 김무선 (한국철도기술연구원 도시철도연구팀)
  • Received : 2018.07.30
  • Accepted : 2018.11.02
  • Published : 2018.11.30

Abstract

The use of 3D printing (Additive Manufacturing) technology has expanded from initial model production to the mass production of parts in the industrial field based on the continuous research and development of materials and process technology. As a representative polymer material for 3D printing, the polyamide-based material, which is one of the high-strength engineering plastics, is used mainly for manufacturing parts for automobiles because of its light weight and durability. In this study, the specimens were fabricated using Selective Laser Sintering, which has excellent mechanical properties, and the flexural characteristics were analyzed according to the temperature of the two types of polyamide 12 and glass bead reinforced PA12 materials. The test specimens were prepared in the directions of $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ based on the work platform, and then subjected to a flexural test in three test temperature environments of $-25^{\circ}C$, $25^{\circ}C$, and $60^{\circ}C$. As a result, PA12 had the maximum flexural strength in the direction of $90^{\circ}$ at $-25^{\circ}C$ and $0^{\circ}$ at $25^{\circ}C$ and $60^{\circ}C$. The glass bead-reinforced PA12 exhibited maximum flexural strength values at all test temperatures in the $0^{\circ}$ fabrication direction. The tendency of the flexural strength changes of the two materials was different due to the influence of the plane direction of the lamination layer depending on the type of stress generated in the bending test.

3D 프린팅 (적층 공정) 기술은 소재와 공정기술의 지속적인 연구개발을 토대로 초기 모형 제작 활용으로부터 현재는 산업현장의 양산형 부품 제작까지 그 쓰임새가 확대되고 있다. 3D 프린팅의 대표적인 고분자 소재로서 고강도 엔지니어링 플라스틱의 하나인 polyamide (폴리아미드) 계열의 소재는 제품의 경량화 및 내구성의 장점으로 자동차용 부품 제작에 주로 활용된다. 이번 연구에서는 적층기법 중 제작품의 물성이 우수한 선택적 레이저 소결 기법 (Selective Laser Sintering)을 적용하여 polyamide 12 (PA12) 및 글라스 비드 (glass bead) 보강 PA12 소재 2가지를 대상으로 시편을 제작하고 온도에 따른 굴곡특성을 분석하였다. 작업 플랫폼 기준으로 $0^{\circ}$, $45^{\circ}$, $90^{\circ}$ 방향으로 각 시편을 제작 후, $-25^{\circ}C$, $25^{\circ}C$, $60^{\circ}C$ 등 3개 시험온도 환경에서 굴곡 테스트를 진행하였다. 그 결과로, PA12 는 $-25^{\circ}C$ 에서 $90^{\circ}$ 제작 방향이, $25^{\circ}C$$60^{\circ}C$에서는 $0^{\circ}$ 제작방향이 최대 굴곡강도를 가졌다. 글라스비드 보강 PA12는 제작방향이 $0^{\circ}$인 겨우 모든 시험온도에서 최대 굴곡강도 값을 보였다. 두 소재의 서로 다른 굴곡강도 변화 경향은 굴곡시험시 발생하는 응력 종류에 따라 적층 레이어 평면 방향에 의한 영향이 서로 다르기 때문으로 판단된다.

Keywords

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Fig. 1. Schematic diagram of SLS [10]

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Fig. 2. Orientation of layers

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Fig. 3. Flexural property test diagram and test specimen definition

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Fig. 4. Mean value and standard deviation of flexural modulus and flexural strength of PA2200 at test temperature of (a) -25 ℃ (b) 25 ℃ and (c) 60 ℃

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Fig. 5. Mean value and standard deviation of flexural modulus and flexural strength of PA2200 with building orientation of (a) 0° (b) 45° and (c) 90°

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Fig. 6. Mean value and standard deviation of flexural modulus and flexural strength of PA3200 GF at test temperature of (a) -25 ℃ (b) 25 ℃ and (c) 60 ℃

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Fig. 7. Mean value and standard deviation of flexural modulus and flexural strength of PA3200 GF with building orientation of (a) 0° (b) 45° and (c) 90°

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Fig. 8. Stress distribution of (a) tensile load case and (b) flexural load case

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Fig. 9. Orientation of (a) tensile stress, (b) shear stress in PA2200 test specimen and (c) shear stress in PA3200GF test specimen of 0° build orientation

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