UNIVERSITY OF LJUBLJANA Faculty of Mechanical Engineering Sandwich panel design suitable for selective laser sintering additive manufacturing A Master’s thesis of the second-cycle master’s study programme in MECHANICAL ENGINEERING – a research and development programme. Pau Vidal Bravo Ljubljana, February 2021 UNIVERSITY OF LJUBLJANA Faculty of Mechanical Engineering Sandwich panel design suitable for selective laser sintering additive manufacturing A Master’s thesis of the second-cycle master’s study programme in MECHANICAL ENGINEERING – a research and development programme. Pau Vidal Bravo Advisor: prof. dr. Jernej Klemenc, univ. dipl. inž. Ljubljana, February 2021 Candidate Pau VIDAL BRAVO MAGISTRSKI STUDIJSKI PROGRAM Il. STOPNJE: MAG ID914 E NASLOV TEME: Konstruiranje sendvic panelov primernih za izdelavo z dodajno tehnologijo selektivnega laserskega sintranja Uporaba dodajnih tehnologij predstavlja revolucijo v izdelavi prototipov in koncnih izdelkov, ker omogoca izdelavo oblik in struktur, ki jih ni mogoce izdelati s tradicionalnimi izdelovalnimi postopki. Dodajne tehnologije so se pojavile na trgu s ciljem zadovoljitve potreb po izdelavi personaliziranih izdelkov ter maloserijskih kompleksnih izdelkov z visoko dodano vrednostjo. Fokus tega magistrskega dela bo usmerjen v dodajno tehnologijo selektivnega laserskega sintranja. Cilj magistrskega dela je razviti konstrukcijo sendvic panela, ki bo lahko uporabljen v nosilnih strukturah, obremenjenih z upogibnirni obremenitvami. Kandidat naj se naprej seznani s tehnologijo selektivnega laserskega sintranja (SLS) na osnovi relevantne literature. Nato naj pregleda zadnje stanje razvoja na podrocju konstruiranja sendvic panelov. Na osnovi pridobljenih znanj naj skonstruira taksne oblike panelov z notranjirni podpomimi strukturami, ki bodo primerni za uporabo v upogibno obremenjenih planamih nosilnih strukturah. Za vsak tip panela naj izvede tri staticne preskuse: nateznega, striznega in tritockovno upogibnega. Eksperimentalne rezultate naj primerja s simulacijami. Za najboljsi(e) panel(e) naj izvede se utripne dinamicne preskuse s ciljem ocene dinamicne zdrzljivosti. Magistrsko delo je treba oddati v jezikovno in terrninoloskopravilnem angleskem jeziku. Rok za oddajo tega dela je sest mesecev od dneva prevzema. MASTER THESIS- MASTER'S DEGREE STUDY No. MAG 11/914 E TITLE Sandwich panel design suitable forselective laser sintering additive manufacturing The use of the additive manufacturing revolutionizes the way to develop prototypes and final parts, because it allows shapes and structures not possible in traditional manufacturing processes. These technologies have been introduced to the market to satisfy the demand of personalized parts with high geometry complexity and small series, high valued products. In this thesis the focused will be put on the Selective Laser Sintering (SLS) additive manufacturingtechnology. The objective of this M.Sc. thesis is to develop a core of a sandwich panel that is useful for application in different structures, which are exposed to bending loads. The candidate should first acquire knowledge on the Selective Laser Sintering (SLS) by studying the relevant literature. Then the state-of­ the-art theoretical and practical topics related to the design of sandwich panels should be reviewed. This should be followed by a design of the most suitable panels that can be used for supporting the bending loads of planar structures. For each case of the panel three kind of static tests should be made, i.e. a compression, a shear and a three-point bending test. The experimental results should be compared to the numerical simulations. For the most promising design(s) the pulsating fatigue tests should finally be carried out to assess the fatigue resistance of such structures. The submitted master thesis must be written in standard English. The master thesis must be submitted six months after it was accepted. Mentor Digitally signed by J ER N EJ JERNEJ KLEMENC 1a�= 2021-01-14 Prof. PhD. Jemei� Klemenc KLEMENC l ' 08:30:48 +01 '00' I hereby confirmthe receipt of the master thesis Date .................................. ..... .. Student Signature .................... I, the undersigned Pau Vidal Bravo, student of the Faculty Of Mechanical Engineering at the University of Ljubljana, with registration number 70085228, author of the written final work of studies, entitled: Sandwich panel design suitable for selective laser sintering additive manufacturing , DECLARE that 1.a) The written final work of studies is a result of my independent work; 2. The printed form of the written final work of studies is identical to the electronic form of the written final work of studies; 3. I acquired all the necessary permissions for the use of data and copyrighted works in the written final work of studies and clearly marked them in the written final work of studies; 4. During the preparation of the written final work of studies I acted in accordance with ethical principles and obtained, where necessary, agreement of the ethics commission; 5. I give my consent to the use of the electronic form of the written final work of studies for the detection of content similarity with other works, using similarity detection software that is connected with the study information system of the university member; 6. I transfer to the UL – free of charge, non•exclusively, geographically and time•wise unlimited – the right of saving the work in the electronic form, the right of reproduction, as well as the right of making the written final work of studies available to the public on the World Wide Web via the Repository of the UL; 7. I give my consent to the publication of my personal data included in the written final work of studies and in this declaration, together with the publication of the written final work of studies; 8. I give my consent to the use of my birth date in COBISS record. In Ljubljana, 12 February 2021 Student's signature: __________________ Acknowledgements I would like to thank my tutor Jernej Klemenc, who has been always very helpful and has always find time for me, even though the great amount of work that he had. From the very begging, he has been very attentive to me. Also, I would like to thank the Ph.D. student Jure Kajbič who has help me a lot during all the master thesis, from the printing to the simulations with Abaqus. Last but not least, I would like to thank my family for all the support that they have given me during all the years of my studies, from the bachelor's degree to now the master thesis. Without their moral and economical support, I could not reach this goal. v vi Declaration 1. I, the undersigned Pau Vidal Bravo, born 26 December 1996 in Girona, a student at the Faculty of Mechanical Engineering at the University of Ljubljana, hereby declare that this master’s thesis titled Sandwich panel design suitable for Selective Laser Sintering additive manufacturing is my own original work created under the supervision of my advisor prof. Dr. Jernej Klemenc. 2. I hereby declare that the submitted electronic copy of this master’s thesis is identical to the printed copy. 3. Pursuant to the provisions of the Copyright and Related Rights Act (Official Gazette of the Republic of Slovenia, No. 21/1995 as amended), I hereby expressly give my permission for this master’s thesis to be published on the websites of the Faculty of Mechanical Engineering and the University of Ljubljana. 4. By signing this Declaration, I grant my permission for this master’s thesis to be made publicly accessible online via the Repository of the University of Ljubljana. By signing this document, I certify that: ‐ the presented text is the product of my own original research in its entirety. ‐ the presented text adheres to linguistic and stylistic conventions and the technical requirements of the Guidelines for Composing Final Theses, meaning that: ‐ the works and opinions of other authors used in this master’s thesis are appropriately cited or acknowledged pursuant to the Guidelines for Composing Final Theses, and ‐ I have obtained the permission for the use of any data and original work reproduced in the text in full (either as text or as a graphic) from their respective authors and duly noted that in the text itself. ‐ I am aware that plagiarism, i.e., the misrepresentation of someone else’s work (be it text or graphics) as my own, is a crime under the Criminal Code of the Republic of Slovenia (Official Gazette of the Republic of Slovenia, No. 55/2008 as amended); ‐ I am aware of the potential repercussions concerning my status at the Faculty of Mechanical Engineering at the University of Ljubljana as per the applicable Rules should plagiarism be proven in connection to the submitted master’s thesis. Ljubljana, 12 February 2021 Signature of the author: __________________ vii viii Abstract (in English) UDC 621.9.048.7:621.762.5:678.6(043.2) Serial No.: MAG II/914 E Sandwich panel design suitable for selective laser sintering additive manufacturing Pau Vidal Bravo Keywords: Selective laser sintering Polyamide 12 Sandwich panel Design Honeycomb structure Lattice structure The use of additive manufacturing revolutionizes the way to develop prototypes and final parts because it allows shapes and structures not possible in traditional manufacturing processes. These technologies have been introduced to the market to satisfy the demand for personalized parts with high geometry complexity and small series, high valued products. In this thesis, the focus has been on the Selective Laser Sintering (SLS) additive manufacturing technology. The objective of this M.Sc. thesis has been to develop a core of a sandwich panel that is useful for application in different structures, which were exposed to compression, shear, bending and fatigue loads. It has been mandatory to first acquire knowledge on the Selective Laser Sintering (SLS) by studying the relevant literature. Then the state-of-the- art theoretical and practical topics related to the design of sandwich panels had been reviewed. This was followed by a design of the most suitable panels that can be used for supporting the bending loads of planar structures, these designs have been made with Solidworks software.