Zero stiffness composite shells using thermal prestress

Zero stiffness composite shells using thermal prestress

Doornenbal, Barend (TU Delft Mechanical, Maritime and Materials Engineering)

Radaelli, G. (mentor)
Herder, J.L. (mentor)
Alijani, F. (graduation committee)

Delft University of Technology

Mechanical Engineering | Mechatronic System Design (MSD)

2018-09-14

Compliant shell mechanisms are thin walled structures that achieve their motion through deformation. Shell mechanisms are of recent interest for designing exoskeletons that are inconspicuous. One of the challenges in designing shell mechanisms is getting as much compliance as possible in certain directions while keeping the other directions sufficiently stiff.

Prestressing is a technique that is used to change the stiffness of compliant mechanisms and it makes it possible to generate compliant mechanisms that have zero or negative stiffness. Seffen et al. have generated a shell with zero stiffness by rolling a metal plate in two perpendicular directions showing that it is possible to generate shell mechanisms without stiffness.

The main disadvantage of this technique is how it limits the different shapes that are possible. The goal of this thesis is to create a compliant shell with more freedom in shape that used the same physical principle to generate a degree of freedom with a much lower stiffness. The method chosen was to use a shell made out a carbon fibre composite that was prestressed with the thermal stresses that are the result of the curing process.

The thesis presents the analytical model and the finite element model that has been used to describe the effects of prestress and the experiments that have been done to verify these models.
 

compliant mechanism
Shell
neutrally stable
zero stiffness
thermal prestress

http://resolver.tudelft.nl/uuid:8d32e3fc-ab46-43c3-a659-4913fad3c4c0

Student theses

master thesis

© 2018 Barend Doornenbal