Saturday, January 3, 2015

Ultra lightweight sandwich panel core

Big Problem


The rising demand for new materials with higher strength to weight ratios has created a dramatic growth in sandwich composite technology. 
Sandwich construction employs a lightweight core that has a flexural strength and flexural modulus far exceeding that of the skin laminates alone. 
The most common type of core material is honeycomb which is used primarily for structural applications in the aerospace industry.

Honeycomb is a series of cells, nested together to form panels similar in appearance to the cross-sectional slice of a beehive. 

In its expanded form, honeycomb is 90-99 percent open space. Honeycomb is lightweight and has good impact resistance. It offers the best strength to weight ratio of all the core materials.

However the main disadvantage of honeycomb type cores used in the Aircraft and Aerospace industries is that of delamination which can cause a catastrophic failure of the vehicle. 
This is caused primarily by the failure of the epoxy adhesives to maintain a bond between the facing skins and the core because of the very small bonding area that honeycomb cores edges offer.

Standard Honeycomb

This is further exacerbated by the fact that honeycomb type cores create pockets of trapped air within the closed cells of the core when the skins are attached. 
The air pressure experienced at high altitudes is much lower than the trapped air within the cells with the result that the skin is pushed away from the inner core by the air pressure. 
Ingress of water into already partially delaminated cells at high altitude freeze into ice particles which expand and force the skin to separate from the core. 
Eventually after many cyclic operations the skin will delaminate. 

Lightning strikes can cause entrapped moisture within the core to immediately turn to steam with catastrophic results to the integral strength of the panels.

The Aerospace Industry remains the greatest consumer of honeycomb materials, whether for civil aircraft, military jets, helicopters, aero-engines or the newer space satellite and launchers.

We have now stretched the limits of honeycomb. 

We have held onto it because there was nothing better and we are now seeing the inability of aircraft and rocketry to operate successfully.

Hexaflex is a new concept in core design which radically overcomes all of the disadvantages that are inherent in honeycomb cores. 

Instead of being made of  single ribbons glued together, Hexaflex is formed from a single sheet or web of core material that has a repeating geometrical design cut out of its surface. 
This leaves a flat template design comprising of inter connected hexagons and rectangles. Fig 1.
By employing a series of alternating folds, the flat design can be folded, concertina style, in upon itself to make a double-layered core wherein the rectangles form a 45 degree angle to the hexagons.
A comparison of the available bonding areas of standard honeycomb and Hexaflex shows that Hexaflex has a bonding area equal to the complete area of a hexagon whilst standard honeycomb has a bonding area equal only to the surfaces of the edges of the hexagon cell it defines.

The architecture of this core material, as a product of its design, has open interstitial galley ways spaced at 120 degrees throughout its thickness.

The Hexaflex core is lacking in compression strength when compared to standard honeycomb. 
This shortcoming is solved by the ability of this design to be injected/infused with syntactic foam into its galley ways, completely filling all voids between the face sheets.

Compression forces can be tailored to optimize the structure by strategically infusing syntactic foam of varying crush strengths.

The high crush strength and low density of syntactic foam makes it an ideal core material for sandwich composites. 

However shear experiments have showed that the bond between a syntactic foam core and composite face sheets could be a weak link in a sandwich design. 

By combining the attributes of Hexaflex and syntactic foam it is possible to create an ultra lightweight core wherein Hexaflex provides the tensile properties and the syntactic foam provides the compression properties.

It may now be possible to eradicate delamination.

Sunday, October 27, 2013

More applications

    Aerospace, automotive, defense, test facilities, industrial machines, marine, nuclear, rail.
  • AEROSPACE Satellites, launch vehicles, space shuttle, morph technology.
  • AUTOMOTIVE Crash test barriers, door and roof panels, double-skinned exhaust manifolds, fairings, heat exchange panels, flexible fuel tank, motorcycle fairings.
  • AVIATION Ailerons, cowlings, doors, flooring, flaps, radomes, rudders.
    arterial stent technology, artificial extra-cellular matrix, capsid engineering. Hernia mesh prosthetics.
  • CONSTRUCTION architectural panels, concrete reinforcement in earthquake prone areas, false ceilings, flexible tubular structures, insulation curtains for hazardous material removal, roof panels, wall panel. 
    MARINE bulkheads, bunks, covers, decks, double skinned hulls, hatches, wave energy framework. 
    MISCELLANEOUS dirigibles, double-skinned oil tanks, flexible body armor, oil pipelines, piping / ductwork with interstitial space, radio frequency shielding, soil stabilization mat, solar energy panels, sound attenuation panels. 
    RAIL Ceilings, doors, energy absorbers/bumpers, floors, partitions. 
    RECREATION INDUSTRY athletic shoes, motorcycles, surfboards, snowboards, tent walls, toy, wake board.
    RESEARCH morphing wing concept, nanotechnology, robotics. 

Tuesday, July 30, 2013

New Concept in the Design & Manufacture of a Prosthetic Latticework.


The use of mesh has become essential in the repair of all hernias. To move forward into a new era of hernia mesh prosthesis  a panel of nine experts in hernia repair and experimental mesh evaluation agreed that new technologies and novel approaches must be investigated and designed.

The aim of this paper is to propose, a new concept in the design & manufacturing of a prosthetic latticework for inguinal, ventral or incisional hernia repair.

The 'smooth' side, having a small pore size, is placed adjacent to the bowel and resists tissue attachment.

The unique geometry of the lattice allows it to stretch in more than one direction and then return to its original shape. Existing hernia meshes are made of relatively stiff and inelastic material. The author strongly believes that these characteristics may be a contributing factor for recurrences and patient discomfort.
The proposed lattice easily assumes the conformity of the abdominal wall musculature anatomy and thus improves the long term comfort and well-being of the patient.

 The 'rough' side, with a more open pore size, is next to the tissues that surround the bowel where tissue incorporation is an advantage. Lattice cell size of 4mm (5/32nds) and thickness of 2mm (5/64ths). Lattice width of 150mm (6”).

The method of manufacture of this surgical lattice is using 3D printing technology. First, a three-dimensional structure is designed using CAD software. The porosity can be tailored using algorithms within the software. The lattice is then realized by using ink-jet printing of polymer powders or through Fused Deposition Modeling of a polymer melt.
The basic materials could be:
• ePTFE. (Expanded polytetrafluoroethylene) The use of ePTFE surfaces in hernia repair reduces adhesions and would reduce the recurrence rate.  This would be the first layer that is printed (smooth side down)
• Polypropylene. This material has been used for the past 20 years because of its stability, strength, inertness and handling qualities. Polypropylene is overprinted on the PTFE layer and provides the basic structure of the lattice.
• Collagen. A final layer of collagen is printed to encourage speedy host tissue incorporation into the latticework.

Potential attributes of lattice.
1. May result in the permanent repair of the abdominal wall, to reinforce and replace tissue for long-term stabilization of the abdominal wall.

2. Ingrowth characteristics that mimic normal tissue healing. May stimulate adequate fibroblastic activity for optimum incorporation into the tissues. May prevent adhesions. The ePTFE protects the edge of the lattice minimizing tissue attachment to the material.

3. Strong. May provide sufficient biomechanical strength to meet physiological requirements in order to permanently protect the fascial defect.

4. Pliable. It has elasticity in more than one dimension, allowing it to stretch in more than one direction and then return to its original shape. Easily assumes the conformity of the abdominal wall musculature anatomy.

5. Handling characteristics should be amenable to laparoscopic instruments.

6. The lattice may have an adequate adhesive quality that requires minimal or no additional fixation, even for large defects.

7. Non-allergenic.

8. Inert.

9. Non-biodegradable.

10. Non-carcinogenic.

11. Cuts easily without fraying.

12. The dimensions and mechanical properties of the proposed lattice can be tailored to provide an effective portfolio of hernia prostheses.

13. No shrinkage

CAD/CAM Technologies.
A number of different methods have been described in literature for preparing porous structures to be employed as tissue engineering scaffolds. Each of these methods presents its own advantages, but none are free of drawbacks.
Because most of the above techniques are limited when it comes to the control of porosity and pore size, computer assisted design and manufacturing techniques have been introduced to tissue engineering.

Monday, January 7, 2013


Yishu Dai 
I still don't' get the concept of hexaflex though, why are we trying to find them, and what's special about them that we're trying to find them?
January 1 at 11:26pm · Like

Bob Burdon 
Welcome to all of my newly acquainted friends and visitors. 
Thank you all so much for joining this group of "Think Tankers" . De Bono would be proud!

Our Quest is to find this honeycomb lattice which I call HEXAFLEX.

This design is elegant and simple in its construction.
Yet for all of its geometrical simplicity it had never been discovered until I serendipitously found it 5 years ago. 

That fact alone is staggering

In that time, with the help of my good friends David, Janice, Kelvin and Seth, a patent was granted in June 2009.

We have identified many possible applications for Hexaflex but there is one thing which continues to elude us.


For all our skill and technological prowess, human engineers still can't match Mother Nature's best designs. Her designs are always simple and elegant

In order to help us focus on this quest I am gathering a collection of images of all natural things which have a degree or two of hexagonality about them. By carefully analysing these images we may gain a clue.

I believe that this geometrical discovery has great significance in science. It could be the precept to precipitate a concept to finally precipitate a paradigm. 

This quest will open a door into another world of possibilities.
We may find its existence in the human body. 
Perhaps it exists in the nanoworld .
Perhaps its the Herpes virus capsid.

Perhaps in your own field of interest/profession you may know where Mother Nature's uses Hexaflex.
Perhaps we could grow stem cells on it.
Perhaps a true mechanical skin.
Perhaps..............Fill in the blank.
Time to flex brain muscles!

Given all the potential of Hexaflex, it is exciting to imagine how this structure will be utilized in the future.

Feel free to explore all aspects of this site. Scroll down to 'Photos' and click on 'See All'. If you are enthused by any particular photo in the album and have a comment that you would like to leave then please feel welcome.
Positive or negative, leave a link, leave a video, upload photos. 
Our think tank will surely reach a critical mass of thoughtful input. 
Feel free to invite your friends to our group. 
January 1 at 11:30pm · Like

Yishu Dai 
thank you i did read this, but i'm so confused about how exactly this design is helpful
January 1 at 11:44pm · Like

Bob Burdon 
To find this exact latticework in natural engineering has been the aim of this quest. 
It has unique properties. 
This latticework is governed by a simple geometrical pattern of rectangles with hexagons. The pattern of the layout evolves from the three dimensional geometric tessalation of rhombic dodecahedrons. This pattern allows this two-dimensional pattern to be folded, concertina style, into the third dimension. 
It is based on pure geometry. 
With that in mind, it became my belief that this latticework had to exist somewhere in Mother Nature's toolbox. 
To date, with a limited number of 3D printed prototypes it can model all the allotropes of carbon. As a molecular modelling kit it has the potential for furthering both research and discovery in nanotechnology where I believe it was hiding all along. 
It mimics the surface of a scale on a butterfly wing.....that could be a line of good enquiry and research.
This design makes an amazing toy for both kids and adults. Our consciousness expands to fill whatever you live in. This toy design is helpful in weaning us away from cubic mentality which can turn us into blockheads. This toy intergrates with LEGO ….call it serendipity.
We live in a carbon world.

Wednesday, July 25, 2012

The Hexaflex Toy

The Hexaflex Toy.
Allow me to introduce to you a new conceptual toy that will open up your imagination to build and shape three dimensional space.
All thanks to the guidance of Serendipity I have reverted back to using the Hexaflex matrix as an educational toy. This toy has all the potential to allow scientists, engineers and children to explore the world of natural engineering and to discover new relationships within Mother Nature's geometry.We are carbon life forms.Carbon forms the basic chain structure that allows biological molecules to achieve their complexity and versatility.
This new conceptual flexible toy emulates the geometry of how carbon atoms join together allowing us to make all the complex natural forms that can be found in the natural macro and nano-world.

Layers of Learning

The Hexaflex toy is a building kit. It is an educational toy that incorporates multiple layers of learning. These layers promote both critical thinking and discovery. 
These layers include:

1. Exploring the world of polyhedra.

2. Discovering the intricacies of Nanotechnology.

3. Creating robotic structures.

4. Integral construction possibilities with Lego.

The kit consists of a collection of flat hexagonal and rectangular tiles made from Nylon that can hinge together with one another. The tiles easily snap together and apart with an audible click. They can be assembled to construct such objects as multiple variable surface curvatures such as spheres, domes, buckyballs,
 nanotubes, torus /doughnuts, terraced planes, rhombic dodecahedrons and parabolic dish structures.

It is also possible to construct a specially designed latticework. This lattice has very novel properties. It is an assembly of an expandable/contractible truss mechanism (Nodlet)which creates a surface whose curvature can be manipulated remotely.The hinges are common throughout which allow an amazing freedom to build anything in nature.

Individual cells of the lattice can be independently opened or closed. Because of the increase in tension forces experienced in robotic applications, individual metal hinge pins can be inserted into the hinge barrel to prevent the hinge joints coming apart.
The tiles also feature bearing holes that accept Lego axle pins. This feature allows the Hexaflex Building Kit based on hexagonal geometry to integrate with Lego orthogonal structures.

Saturday, February 18, 2012

Toroidal Armature

Sunday, February 28, 2010

Toroidal Armature

The matrix shown in tubular form showing zig-zag, armchair and chiral.

I believe that Hexaflex can be used as a toroidal armature in order to hold the windings of a toroidal coil in a pre-ordained geometrically governed set of three spiral paths moving around the toroid.
One of these spirals is that of the Rodin coil.

Once the angle is chosen and set into the armature, two other winding paths are formed set at 120 degrees from the original spiral angle. I wonder what results three windings would create.


  1. Scott OnstottJul 18, 2010 04:31 PM
    I am amazed by the potentials of hexaflex. Have you ever made a torus with hexaflex? What would the 2D pattern look like? It's fascinating that channels would be available in a hexaflex torus. Perhaps the wires could be wrapped into these "venting channels"?
  2. Aloha Scott,
    Here you will see hexaflex rolled up into a tube.Now imagine joining the two ends of the tube to create a torus. So the 2d pattern is hexaflex as seen in my blog.
    Hope this helps.
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  20. The problem with this trellis/lattice shown here is that a "tube torus" is the wrong model. The inner 'hole' should converge infinitely in the manner of a cone infinitely approaching/compressing to a point with smaller and smaller circles spaced smaller and smaller apart.
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