Thin-walled structures for energy absorption

Thesis

This thesis considered three types of new and improved high-performance energy absorbing devices for either compression or bending applications. These improvements were achieved by only altering their initial geometries for desired failure modes. Three types of proposed energy absorbing structures are as follows.

First, origami initiators were added to tubes with concave cross-sections. This new type of geometries, named as origami concave tubes, successfully triggered a reliable progressive buckling failure, which is uncommon for tubes with concave cross-sections. Origami concave tubes achieved ultra-high energy absorption and relatively low peak force. A comprehensive numerical, experimental, and theoretical analysis was conducted on the square, traditional concave, and origami concave tubes, which showed origami concave tubes achieved 3.3 times of specific energy absorption of square tubes. Additional to the huge improvement, it was illustrated that origami concave tubes can approach the theoretical limit of energy absorption through progressive buckling failure.

Second, thin-walled tubes with corrugated cross-section instead of traditional circular tubes were proposed for inversion. Comparing to circular tubes, the introduction of corrugation not only increased specific buckling force and reduced imperfection-sensitivity of tubes, but also decreased load needed for inversion process. In consequence, thin corrugated tubes could be inverted significantly more reliably, and even allowed practical frictional contact and geometric imperfection, which was not achieved or claimed before for tube inversion. A comprehensive numerical, experimental, and theoretical analysis was carried out on thin circular and corrugated tubes inversion, and validated the effectiveness of the new design. Thin corrugated tube inversion also reaches the theoretical limit of energy absorption.

Third, a series of novel bending devices of beams, panels, arches, and shells using origami technique were developed. These bending devices can provide more constant bending resistance and overall higher energy absorption than conventional open-section beams. Numerical simulations and experiments were used to validate these designs, which showed that properly designed origami bending devices can achieve 23.0%-40.0% increase of energy absorption and 12.7%-20.7% lower load uniformity than those of a conventional beam.

Authors: Li, Y

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Keywords: energy absorption; structures; origami