Aircraft Structures

Lecture

Lecturer: Prof. Dr.-Ing. Sebastian Heimbs

When: Summer semester, Thursdays 08:00 - 09:30

Where: HB 35.1 (IFL)

Excercise

Responsible: Prof. Dr.-Ing. Sebastian Heimbs

When: Summer semester, Thursdays 09:45 - 10:30

Where: HB 35.1 (IFL)

What do all aeroplanes have in common, regardless of their size, propulsion technology, aerodynamic properties or area of application? They must be designed, engineered and built. The lecture ‘Konstruktion von Flugzeugstrukturen’ (Aircraft Structures) (3 SWS / 5 ECTS) is therefore the central lecture in the Master's programme in Aerospace Engineering, in which students learn how an aircraft is actually built, what it consists of, how it is designed – and also why (keyword: dimensioning load cases and certification requirements).

Die Konstruktionsprinzipien von Flugzeugrumpf, Flügel und anderen Strukturen — The design principles of aircraft fuselages, wings and other structures are explained in detail (Credit: Sebastian Heimbs)

This lecture was completely redesigned and modernised by Prof. Heimbs, who comes from Airbus Airframe Engineering. In keeping with standards of aircraft engineering business, the lecture materials are entirely in English (although the lecture itself is held in German). It addresses all topics related to aircraft structural design: from regulatory constraints, the properties and selection of typical aviation materials, joining techniques and stiffening concepts to the design of all relevant aircraft components and the final assembly of the aircraft. In other words, it is the complete comprehensive programme that provides not only the knowledge to participate in discussions within the aircraft industry, but also an understanding of why aircraft designs, construction methods and material selections are made in the way they are. The associated exercises allow students to apply what they have learned.

Rumpfkonstruktion des Airbus A350 als Beispiel für eine Mischbauweise mit Metall- und Faserverbundwerkstoffen und unterschiedlichen Verbindungstechniken — Airbus A350 fuselage construction as an example of a hybrid construction using metal and fibre composites and different joining techniques (Credit: Sebastian Heimbs)

Why, despite the widespread use of fibre composites, are wing leading edges still almost always made of aluminium? Why are aircraft noses almost always made of the exotic material quartz fibre? Why are riveted joints still found everywhere in aircraft construction today, and how are these rivet spacing distances chosen? Why are the two most widely used aircraft construction materials – aluminium and carbon fibre reinforced composites – never found in direct combination? Why are there so many stiffeners in the longitudinal and circumferential directions, and how is their spacing determined? Where do the loads that form the basis of design calculations come from? How is the fact that damage can occur during operation or due to fatigue dealt with, while still ensuring the highest possible level of safety?

We look forward to discussing this and much more with students in the lecture. You can look forward to a very practical lecture that thrives on passing around samples and components to touch and analyse. The IFL has a very large inventory of aircraft structures, so it's worth heading out to the airport campus on Thursday mornings to see real fuselage shells, wings, doors and even entire fuselage barrels from various aircraft – touching is explicitly allowed! And what we can't demonstrate ourselves will be visualised in a practical way with videos.

Schadenstoleranz — Exemplary images from the lecture chapter of damage tolerance: crack propagation in metal (left) and fibre composites (right) (Credit: Sebastian Heimbs)

That's not all. We are delighted to be able to offer students attending this lecture at TU Braunschweig the following:

The lecture is given by lecturers with decades of industry experience in the field of aircraft structures, who provide exciting insights: Prof. Heimbs (formerly Airbus) traditionally invites two additional guest lecturers from Airbus to give lectures on adhesive technology in aircraft construction as well as loads and aeroelasticity.
Practical relevance is emphasised through countless samples and components that can be touched in the lecture room and in the large component and testing hall of the IFL, as well as through exercises accompanying the lectures.
As another exciting highlight, we offer a two-day excursion every year to experience the lecture content in real life at the Airbus plants in Bremen and Hamburg, where the production, equipment and final assembly of aircraft structures can be observed up close. Meetings with Airbus Engineering and the Human Resources department regarding working in the aircraft industry, as well as a joint dinner, round off this excursion as an unforgettable experience

Rumpftonne mit Centre Wing Box — One of the exhibits in the IFL test hall that will be analysed during the lecture: fuselage barrel with centre wing box (Credit: Sebastian Heimbs)

Werksbesichtigung in den Airbus-Werken Hamburg und Bremen sowie im ZAL

The lectures (2 SWS) are divided into the following chapters:

Introduction
General overview & fundamentals: Regulations and certification specifications, ATA-chapters, A/C sections, coordinate systems, test pyramid, TRL levels
Aircraft materials: metals, composites, fibre-metal laminates, sandwich structures, corrosion & surface protection
Structural joints: bolted, welded, bonded joints
Stiffened structures, structural stability & buckling
Loads and aeroelasticity for aircraft structural design: ground loads and flight loads analysis
Structural damage & damage tolerance: metals and composites, crack propagation, stress intensity factors, no-growth policy
Aircraft components: Design and sizing of fuselage, doors, windows, cabin, wing-fuselage joint, wings, wing movables, empennage,
Aircraft structure final assembly
Practical example

In the exercises (1 SWS), we apply the methods learned to specific examples in the design of aircraft structures, such as:

Calculation of sandwich structures
Sizing of riveted joints
Sizing of adhesive joints
Buckling analysis of stiffened aircraft structures
Load analysis
Industrial example

Laboratory module

Are lectures and calculation exercises too theoretical for you, and would you prefer to conduct structural tests in the laboratory yourself? We understand. That is why we offer the laboratory module (2 SWS) for the lecture ‘Konstruktion von Flugzeugstrukturen’, where exactly that happens in the IFL test hall.

Two different types of tests are typically carried out in this laboratory module, using state-of-the-art modern testing and measurement technology. One of these typically relates to the damage tolerance of aircraft structures. In the past, cyclic tests were carried out on metal samples to measure and evaluate crack propagation, and impact tests were carried out on fibre composite samples to determine the residual strength after impact damage. After impact loading on the drop tower and non-destructive ultrasonic testing, the damaged fibre composite samples are subjected to compressive loading (CAI, compression after impact) in order to evaluate the influence of increasing damage on residual strength. Alternatively, a test in the field of dynamic structural behaviour (static vibration test) is offered: quasi-static bending tests and dynamic vibration tests are carried out on a scaled wing profile in order to experimentally determine natural frequencies and eigenmodes for the structural design.

‘Konstruktion von Flugzeugstrukturen mit Labor’ (total with lecture/exercise/laboratory 5 SWS / 7 ECTS):

The laboratory course involves the independent preparation, execution and evaluation of two experiments in the test hall and in the IFL's materials diagnostics laboratory. A graded report and colloquium on the completed laboratory experiments are included in the final grade along with the exam result.

Laborversuch zur Rissausbreitung in Metall — Laboratory test on crack propagation in metal (Credit: Sebastian Heimbs)

Laborversuch zur Impact-Schädigung und Restfestigkeit von Faserverbundwerkstoffen, mit Fallturmversuchen, Ultraschallanalyse und Druckversuchen — Laboratory test on impact damage and residual strength of fibre composites, with drop tower tests, ultrasonic scans and compression-after-impact tests (Credit: Sebastian Heimbs)

The highest possible quality of teaching and continuous improvement are very important to us, which is regularly recognised by students in their teaching evaluations and makes this course ‘Konstruktion von Flugzeugstrukturen’ a very popular lecture. Here are the results of the teaching evaluations for the lecture from the last few semesters:

SoSe 2023: Total score 4,8 / 5 points

SoSe 2024: Total score 4,8 / 5 points

SoSe 2025: Total score 4,9 / 5 points

Prerequisites, relation to other lectures

There are no specific prerequisites for successful participation.
The chapters on materials and corrosion draw on knowledge acquired in the materials science lecture, but apply it in the specific, practical context of aircraft construction.
Due to the limited time available in one semester, the focus is on the various design principles mentioned above at the component level. An entire aircraft is not calculated; for this, reference is made to the lectures ‘Entwerfen von Verkehrsflugzeugen’ and ‘Entwerfen von Verkehrsflugzeugen 2’.
Finite element analyses as a typical tool for aircraft structure calculation are not covered within the limited scope of this lecture; for this, please refer to the lectures ‘Finite-Elemente-Methoden’ and ‘Finite-Elemente-Methoden 2’.

Language

Lecture: German
Lecture notes and slides: English

Exam

Written exam: 90 minutes (short questions + calculation tasks)
If the laboratory module is also attended: graded reports and colloquium on the laboratory experiments (this grade accounts for 6/11 of the overall module grade, the written examination accounts for 5/11)