MEng Project

Design and manufacturing of a bioinspired adaptive structure with enhanced damage tolerance

Project Overview:

Nature frequently offers the most elegant and effective solutions in the field of engineering.  My final year project took inspiration from one of nature's wonders, the intricate and resilient structure of insect wings. I explored the fascinating mechanics behind dragonfly wings, which despite their delicate appearance, exhibit remarkable damage tolerance. The project aimed to decode the secrets of these wings, how they manage to control crack propagation without any healing mechanisms, and translate those insights into the design of an innovative, bioinspired structure. By leveraging advanced 3D printing technologies and material selection, I aimed to replicate the adaptive resilience of these natural structures, potentially paving the way for breakthroughs in fields like aerospace and robotics.

Project Objectives:

The primary objective of this project was to bridge the gap between natural and engineered structures by understanding the mechanisms behind the damage tolerance of insect wings. I aimed to design and create a structure that not only mimics the fracture resistance of dragonfly wings but also offers practical applications in modern engineering.

Research and Concept Development:

To achieve this, I began with an in-depth study of dragonfly wings, focusing on how their micro joints at vein intersections influence crack behavior. These joints play a crucial role in redirecting and arresting cracks, preventing catastrophic failure despite the wings' fragile appearance.

Design and Prototyping:

Leveraging the insights gained from my research, I moved on to the design phase. Using CAD software, I developed models that replicated the key structural elements of the wings, particularly the veins and joints. These models were then brought to life through advanced 3D printing techniques, utilising materials with varying properties to closely mimic the flexibility and rigidity found in nature.

The initial specimen design.
The updated version of the initial specimen design.
The final specimen design.
To achieve multiple material specimens, the Stratasys Objet260 Connex for PolyJet 3D printing marked a significant improvement in replicating the complex structure of dragonfly wings.
PolyJet 3D printed specimens on printers bed.
WaterJet cleaning station used to wash off the support material 
Inside the WaterJet cleaning station with a sample.

Testing and Analysis:

The prototypes were subjected to rigorous tensile testing to observe how cracks propagated through the structure under stress. This testing was crucial in evaluating the effectiveness of the bioinspired design and refining the models based on the observed outcomes.

The tensile testing was carried out by a Tinius Olsen testing machine recording live data on the computer.

Key Outcomes:

The final prototypes demonstrated enhanced damage tolerance, with the ability to redirect or arrest cracks, much like their natural counterparts. These results not only validate the effectiveness of biomimicry in engineering but also open the door to new applications in fields that require resilient and adaptive structures.

Initial results were failures due to poor adhesion and materials.  Updated methods were used including silicone pouring and PolyJet printing to simulate the structures better.

Oomoo 25 silicone pouring.
Silicone Design 1: Flexible.
Silicone Design 2: Rigid.

The silicone method after improvements proved ok but due to high times required to break and uncontrollable membrane thickness, the method was rejected.

PolyJet Printed Design 1: Flexible.
PolyJet Printed Design 2: Rigid.

Moving on with PolyJet printed specimen, some successful tests were performed. The two samples shown above are just some of the many samples tested overall.

Red circles indicate Flexible joints placed on Rigid Structure and Red squares indicate Rigid Joints placed on Flexible Structure

Learning and Future Applications:

This project has been an invaluable learning experience, deepening my understanding of material science, structural analysis, and the potential of biomimicry in modern engineering. The knowledge gained here could have significant implications for designing future technologies, from more resilient aerospace components to adaptive robotic systems.