# Honeycomb structures vs shear stress

Honeycomb structures are made of top and bottom shells and honeycomb geometry at core. In terms of bending load, maximun normal strains take place on top and bottom hence, sheet parts can support them as expected.

However maximun shear strain take place at the center of the cross section which coincide honeycomb structure. As I know, stiffness of the honeycomb very low even negligible. So, what is the idea behind shear stiffness of a honeycomb structure?

Engineering Asked on November 15, 2021

When we talk about shear stress, the first equation comes to our mind will most likely be $$f_v = V/A$$, which, in fact, is the average shear stress, not the maximum. Then, we realize for shear on irregular shape, the best way to determine shear stress is using the shear formula, $$tau = dfrac{V cdot Q}{I cdot b}$$. For this case, you need to workout $$Q$$ and $$I$$, before you can say the honeycomb section is weak, or not, compared to the normal stresses it can resist. Good luck in finding those parameters :)

Answered by r13 on November 15, 2021

A honeycomb member has usually hexagonal pattern shear members. Because it is closest to an isotropic solid member within the constrains of manufacturing.

Lets imagine we put a honeycomb Formica door flat and use it as a beam supporting 100lbs at the center, which will have 50lbs shear at support.

If the support end cuts the hexagons exposing the diagonal blades at abutment, they are under out of plane shear and torque, which they can poorly take and will rotate into a mechanism, starting thee chain of collapse in the entire door.

However as has been said by alephzero these 60 degree lose blades are contained in a solid frame such as a 2in solid wood and they won't develop the rotation mechanism and the door will act very stiff, supporting the load.

Why do we use the honeycomb slabs like concrete ceilings, parking slabs, shopping mall floors, is because it is the most efficient use of material for large span slabs. For a slab to have a large 'I', it needs most of material on top and bottom and the shear can be taken care of hollow, lightweight honeycomb.

Answered by kamran on November 15, 2021

As I know, stiffness of the honeycomb very low even negligible.

That is only correct if all the edges of the honeycomb are free.

If the top and bottom of the honeycomb are constrained by bonding to the face plates, the honeycomb can not "squash flat" with negligible stiffness, and it uses the material very efficiently to resist shear, because applying a "global" shear strain means that the walls of the honeycomb are in either tension or compression.

Honeycomb structures can be much stiffer than solid metal with the same weight. I have used 2m x 1m sheets of aluminium honeycomb (with top and bottom sheets) which are light enough for one person to pick up and carry around easily, but stiff enough and strong enough to stand on without damaging then, if they are supported at each end and used as a 2m long beam.

Answered by alephzero on November 15, 2021

## Related Questions

### How can I make an uncalibrated flow meter for water flows of a few liters per hour

4  Asked on July 26, 2021

### Why is plastic deformation a non-linearity if I am using Bilinear hardening to model it in FEA?

1  Asked on July 25, 2021 by rameez-ul-haq

### How to reduce surface friction when pushing a gear sideways in shaft direction

1  Asked on July 25, 2021 by lascooter

### Looking for locking “lanyard” reel mechanism

2  Asked on July 25, 2021 by maxmclau

### Derivation of expression for strain in a beam that experiences transverse vibrations

1  Asked on July 25, 2021

### Why are railroad tank cars bent in the middle?

3  Asked on July 24, 2021 by lukas_skywalker

### Electronic component datasheet handling

2  Asked on July 24, 2021 by isuru-thiwanka

### How can we model viscoplastic softening using slider, dashpot & springs?

0  Asked on July 24, 2021 by tushar-chaturvedi

### Networked Control

0  Asked on July 23, 2021 by shoaib-muhammad

### Increasing the style spline resolution

1  Asked on July 23, 2021

### Single Split Air Conditioner & Supply/Exhaust Fan

1  Asked on July 23, 2021 by ha-e

### Temperature Question

0  Asked on July 23, 2021 by kevin-zefi

### Force necessary to resist motion due to torque on a drum brake

0  Asked on July 23, 2021

### Delivering RPM from a fixed wheel to a moving wheel

1  Asked on July 23, 2021

### Durability & air-tightness of PUR tube on barbed air port

0  Asked on July 22, 2021 by user199309

### Why were engineers negligent in the 1981 Hyatt Regency walkway collapse?

4  Asked on July 22, 2021

### Big Beam LVL or Glu Lam load capacity to support a gymnast

1  Asked on July 21, 2021

### incompressible fluid approximation and fluid vs sound velocity

2  Asked on July 21, 2021

### Program name of this buckling modeling

0  Asked on July 21, 2021 by razi-awad

### Reduce high pitched noise from idle stepper motor

1  Asked on July 20, 2021 by jack-campbell

### Ask a Question

Get help from others!