Doctoral Thesis

Optimisation of motorcycle frame from composite materials considering manufacturing technology

Final Thesis 13.12 MB Summary of Thesis 2.93 MB

Author of thesis: Ing. Lukáš Gregor, Ph.D.

Acad. year: 2025/2026

Supervisor: doc. Ing. Jan Zouhar, Ph.D.

Reviewers: doc. Ing. Bc. Zdeněk Padovec, Ph.D., doc. Ing. Soňa Rusnáková, Ph.D.

Abstract:

This dissertation focuses on the optimisation of a motorcycle frame made of carbon-fibre
reinforced polymers (CFRP). The objective is to validate a design methodology for
lightweight and structurally efficient composite structures using topology optimisation, while
simultaneously accounting for laminate manufacturability. Structural requirements were
defined in terms of torsional, longitudinal, and lateral stiffness, as well as safety under critical
operating conditions such as braking, jump landing, and cornering. The baseline frame,
manufactured using prepreg–autoclave technology, was analysed, and a design space for
topology optimisation was established. The optimisation results were subsequently
incorporated into the structural design with the dual aim of preserving manufacturability and
reducing the number of assembly parts. The optimised frame achieved a 128 % increase in
torsional stiffness, a 140 % increase in lateral stiffness, and a 67 % increase in longitudinal
stiffness, while simultaneously reducing critical stress concentrations and achieving a 2 %
weight reduction with an unchanged laminate lay-up. The results demonstrate that the use of
topology optimisation as a supporting tool in the design of composite structures represents
an effective pathway for the development of lightweight yet structurally safe CFRP
components.

Keywords:

CFRP, topological optimisation, motorcycle, simulation, FEM, composite, frame

Date of defence

15.12.2025

Result of the defence

Defended (thesis was successfully defended)

znamkaPznamka

Process of defence

The dissertatiton was of a very good scientific and professional level and brings new knowledge in the field of production technology, testing and modeling of properties of composite materials. Particularly higly valued are the parts describing and solving the area of modeling and solvintg the stiffness of a motocycle frame. A partial deficiency in the work is the absence of some parameters and description of the technology of production of a composite frame due to the effort to keep the production technology secret.

Language of thesis

English

Faculty

Fakulta strojního inženýrství

Department

Institute of Manufacturing Technology

Study programme

Manufacturing Technology (D-STG-P)

Composition of Committee

doc. Ing. Antonín Záděra, Ph.D. (předseda)
doc. Ing. Soňa Rusnáková, Ph.D. (člen)
doc. Ing. Bc. Zdeněk Padovec, Ph.D. (člen)
doc. Ing. Karel Kouřil, Ph.D. (člen)
doc. Ing. Petr Porteš, Ph.D. (člen)
pplk. doc. Ing. Zbyněk Studený, Ph.D. (člen)
doc. Ing. Dalibor Rozehnal, Ph.D. (člen)
Assoc. Prof. Dipl.-Ing. Dr. Ewald Fauster (člen)

Supervisor’s report
doc. Ing. Jan Zouhar, Ph.D.

The dissertation by Ing. Lukáš Gregor presents a comprehensive and technically high-quality research focused on the design and optimisation of a motorcycle frame made of composite materials. The work was carried out within the framework of a research project in which Brno University of Technology was a co-investigator, and which was successfully defended. This fact confirms the relevance and contribution of the research not only to academia but also to industrial practice.

Regarding the content and structure of the thesis:

The thesis is clearly structured into ten chapters, which logically follow from the introduction through the literature review, experimental part, numerical analyses, to the conclusions. The author has demonstrated a deep understanding of composite materials, their mechanical properties, manufacturing technologies, and structural optimisation methods. The literature review is extensive, up-to-date, and includes both theoretical knowledge and practical applications.

Regarding methodology and experimental part:

The doctoral candidate chose a methodology that combines numerical simulations, topology optimisation, experimental measurements, and practical prototype manufacturing. A significant contribution is the validation of the material model using the ARAMIS DIC system, which demonstrates the author's multidisciplinary approach. Work with CAD systems, 3D scanning, fixture design, and part manufacturing including CNC programming, tool selection, and cutting conditions far exceeds standard engineering activities.

Regarding results and contribution:

The results are supported by both numerical simulations and experimental measurements. The optimised frame shows significant improvements in torsional, lateral), and longitudinal stiffness while simultaneously reducing weight. The work contributes to science particularly in the area of linking optimisation methods with real manufacturing technologies, which remains an underexplored topic in composite structure design.

Regarding independence and professional level:

The author has demonstrated a high degree of independence, technical proficiency, and the ability to connect theoretical knowledge with practical implementation. He designed, manufactured, and tested most of the components himself, which proves his ability to lead a complex technical project. The thesis is written in professional language, stylistically refined, and in English, which increases its international applicability.

Regarding publication activity:

The author has published the results of his work in several peer-reviewed journals indexed in WoS and Scopus and actively participated in international conferences. This publication activity confirms the scientific relevance of the work.

Conclusion:

The dissertation by Ing. Lukáš Gregor meets the requirements for a doctoral thesis both in terms of professional and formal aspects. The author has demonstrated the ability to conduct independent scientific research, a multidisciplinary approach, and high technical expertise. The work has significant contributions to both science and practice.

Recommendation:

Based on the above, I recommend the dissertation by Ing. Lukáš Gregor for defense and propose the awarding of the academic degree “Doctor” (Ph.D.).

Grade proposed by supervisor: A

Reviewer’s report
doc. Ing. Bc. Zdeněk Padovec, Ph.D.

viz. posudek v PDF
File inserted by the reviewer Size
Posudek oponenta [.pdf] 560,97 kB

Reviewer’s report
doc. Ing. Soňa Rusnáková, Ph.D.

viz. posudek v PDF
File inserted by the reviewer Size
Posudek oponenta [.pdf] 221,70 kB

Responsibility: Mgr. et Mgr. Hana Odstrčilová