Composites Research

The Korean Society for Composite Materials (한국복합재료학회)
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GF/PC Composite Filament Design & Optimization of 3D Printing Process and Structure for Manufacturing 3D Printed Electric Vehicle Battery Module Cover

전기자동차 배터리 모듈 커버의 3D 프린팅 제작을 위한 GF/PC 복합소재 필라멘트 설계와 3D 프린팅 공정 및 구조 최적화

  • Yoo, Jeong-Wook (Department of Polymer Science and Engineering, Sungkyunkwan University) ;
  • Lee, Jin-Woo (Department of Polymer Science and Engineering, Sungkyunkwan University) ;
  • Kim, Seung-Hyun (School of Mechanical Engineering, Sungkyunkwan University) ;
  • Kim, Youn-Chul (School of Chemical Engineering, Sungkyunkwan University) ;
  • Suhr, Jong-Hwan (Department of Polymer Science and Engineering, Sungkyunkwan University)
  • Received : 2021.07.23
  • Accepted : 2021.08.30
  • Published : 2021.09.03
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Abstract

As the electric vehicle market grows, there is an issue of light weight vehicles to increase battery efficiency. Therefore, it is going to replace the battery module cover that protects the battery module of electric vehicles with high strength/high heat-resistant polymer composite material which has lighter weight from existing aluminum materials. It also aims to respond to the early electric vehicle market where technology changes quickly by combining 3D printing technology that is advantageous for small production of multiple varieties without restrictions on complex shapes. Based on the composite material mechanics, the critical length of glass fibers in short glass fiber (GF)/polycarbonate (PC) composite materials manufactured through extruder was derived as 453.87 ㎛, and the side feeding method was adopted to improve the residual fiber length from 365.87 ㎛ and to increase a dispersibility. Thus, the optimal properties of tensile strength 135 MPa and Young's modulus 7.8 MPa were implemented as GF/PC composite materials containing 30 wt% of GF. In addition, the filament extrusion conditions (temperature, extrusion speed) were optimized to meet the commercial filament specification of 1.75 mm thickness and 0.05 mm standard deviation. Through manufactured filaments, 3D printing process conditions (temperature, printing speed) were optimized by multi-optimization that minimize porosity, maximize tensile strength, and printing speed to increase the productivity. Through this procedure, tensile strength and elastic modulus were improved 11%, 56% respectively. Also, by post-processing, tensile strength and Young's modulus were improved 5%, 18% respectively. Lastly, using the FEA (finite element analysis) technique, the structure of the battery module cover was optimized to meet the mechanical shock test criteria of the electric vehicle battery module cover (ISO-12405), and it is satisfied the battery cover mechanical shock test while achieving 37% lighter weight compared to aluminum battery module cover. Based on this research, it is expected that 3D printing technology of polymer composite materials can be used in various fields in the future.

전기자동차 시장이 성장함에 따라 배터리 효율을 증가시키기 위해 차량 경량화 이슈가 대두되고 있다. 이에 전기자동차 배터리 모듈을 보호하는 배터리 모듈 커버를 기존 알루미늄 소재에서 알루미늄 대비 절반 수준의 무게를 가지는 고강도/고내열성 고분자 복합소재로 대체하고자 한다. 또한 복잡한 형상에 대한 제약이 없고, 다품종 소량생산에 유리한 3D 프린팅 기술을 접목하여 기술 변화가 빠른 초기 전기자동차 시장에 대응하고자 한다. 복합소재 역학에 기반하여 압출기를 통해 가공한 단섬유 GF(glass fiber)/PC(polycarbonate) 복합소재 내 유리섬유의 임계길이(critical length)가 453.87 ㎛임을 도출하였고, 사이드 피딩(side feeding) 방식의 가공법을 택함으로써 기존 365.87 ㎛이었던 잔류섬유길이를 향상시킴과 동시에 분산성을 향상시켰다. 이에 30 wt%의 GF가 함유된 GF/PC 복합소재로 인장강도(tensile strength) 135 MPa, 탄성계수(Young's modulus) 7.8 MPa의 최적의 물성을 구현하였다. 또한 3D 프린팅 필라멘트가 상용 필라멘트 규격인 두께 1.75 mm, 표준편차 0.05 mm를 만족하기 위해서 필라멘트 압출 조건(온도, 압출속도)을 최적화하였다. 제작된 필라멘트를 통해 기공률을 최소화하며 강도를 최대화하고, 동시에 생산성 향상을 위해 프린팅 속도를 최대화하는 다중 최적화 문제를 통해 3D 프린팅 공정조건(온도, 프린팅 속도)을 최적화하였고, 이로써 기존 상용화 되어있는 동일 소재 필라멘트 대비 인장강도 11%, 탄성계수 56%가 향상된 결과를 얻었으며, 출력물의 후처리(post-process)를 통해 후처리 전 대비 인장강도 5%, 탄성계수 18%를 추가로 향상시켰다. 끝으로 유한요소해석(finite element analysis, FEA) 기법을 활용하여 전기자동차 배터리 모듈 커버의 시험 규격(ISO-12405)의 Mechanical Shock test의 기준을 만족하도록 배터리 모듈 커버의 구조를 최적화하였고, 이로써 배터리 커버 시험규격을 만족하면서 동시에 알루미늄을 사용했을 때 대비 37%의 경량화를 달성하였다. 해당 연구 결과 및 연구 방법을 활용하여 향후 다양한 분야에 고분자 복합소재 3D 프린팅 기술이 활용될 수 있을 것으로 기대된다.

Keywords

Acknowledgement

본 연구는 국토교통부/국토교통과학기술진흥원의 지원으로 수행되었음(과제번호 21CTAP-C157949-02). 본 연구는 과학기술정보통신부 및 과학기술 일자리진흥원 2019년 연구성과사업화지원사업의 지원을 받아 수행하였음(2019K000359).

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