Nose cone, energy absorption and design

[mortimer]

How is the nose cone constructed and designed, and how does it absorb energy during an impact?

What materials is used?

[marcush.]

I´d think this sums it up really:

http://www.formtech-composites.co.uk/f1 ... study.html

http://www.formtech-composites.co.uk/do ... d%20F1.pdf

[manchild]

[youtube]http://www.youtube.com/watch?v=a2H_leY_Q8k[/youtube]

[mortimer]

thank you for the links, although I'm still a bit confused. So nose cone is usually made of layered composite materials which absorbs the energy? I was told that there should be some kind of impact attenuator, often a honeycomb structure..

[marcush.]

thank you for the links, although I'm still a bit confused. So nose cone is usually made of layered composite materials which absorbs the energy? I was told that there should be some kind of impact attenuator, often a honeycomb structure..

the nosecone is made of aluminiumhoneycomb between prepreg carbonfibrelayups...
so if not good for anything ,the USF1 website gives good insight into this:

http://www.usgpe.com/news/in-detail-bui ... -nose.html

and expensive said all was rubbish they did ...it is quite educational ..right?

[manchild]

As the slow motion of video shows, it is made mainly of carbon fiber, and designed to shred to small pieces. It does not disintegrates fully on any impact. Depending on speed and angle, it can disintegrate only a bit, which is often seen in real racing as the tip of the nose missing or a hole.

Here is another video.

[youtube]http://www.youtube.com/watch?v=Mc0wFyCIDfE[/youtube]

http://www.f1technical.net/articles/11

[xpensive]

From Article 16.2 to in the FIA Tech regs;

For the purposes of this test, the total weight of the trolley and test structure shall be 780kg (+1%/-0) and
the velocity of impact not less than 15 metres/second.
The resistance of the test structure must be such that during the impact :
- the peak deceleration over the first 150mm of deformation does not exceed 10g ;
- the peak deceleration over the first 60kJ energy absorption does not exceed 20g ;
- the average deceleration of the trolley does not exceed 40g ;
- the peak deceleration in the chest of the dummy does not exceed 60g for more than a cumulative
3ms, this being the resultant of data from three axes.

And marcush, they broke their nose, didn't they?

[marcush.]

From Article 16.2 to in the FIA Tech regs;

For the purposes of this test, the total weight of the trolley and test structure shall be 780kg (+1%/-0) and
the velocity of impact not less than 15 metres/second.
The resistance of the test structure must be such that during the impact :
- the peak deceleration over the first 150mm of deformation does not exceed 10g ;
- the peak deceleration over the first 60kJ energy absorption does not exceed 20g ;
- the average deceleration of the trolley does not exceed 40g ;
- the peak deceleration in the chest of the dummy does not exceed 60g for more than a cumulative
3ms, this being the resultant of data from three axes.

And marcush, they broke their nose, didn't they?

I feel mine bleeding as well after waving their flag until the very end..it seems I
do have a soft spot for the hope and helpless...makes me think again...seriously.

[riff_raff]

mortimer,

impact structures like sidepods, nosecones, etc. mitigate impact effects by absorbing and dissipating kinetic energy thru accumulation of strains within the impact structure, and then rapid (and hopefully harmless) release of that strain energy at structural failure.

This transfer of energy during the rapid, "controlled" collapse of the impact structure serves to reduce the max deceleration rate of the impact event. It's the peak negative g's of the sudden impact that cause injury (F=MA), and not so much the outright impact velocity.

Composite structures have both pluses and minuses with regards to failure modes. They can dissipate large amounts of strain energy when they fail if designed to do so. But they tend to fail very abruptly when they finally do let go (ie. they tend to have a very small margin between their yield and ultimate limits) and they are also very stiff structures. I believe they typically fail through inter-laminar shearing, peeling and compressive buckling.

Aluminum or steel structures are less stiff and strong. But they have a much greater margin between their yield and ultimate limits (ie. their elongation rates are much higher). So these metal structures many times tend to bend and plastically deform without completely fracturing like carbon fiber composites do. So their failure mechanisms tend to be a little more graceful.

The best impact structures are usually a combination of carbon fiber laminates and an aluminum honeycomb core.

I'm not much of a structures expert, so maybe someone else with more composite structures knowledge can correct any errors in my post.

Hope that helps anyway.
riff_raff

[mortimer]

I know that a metall is less brittle then a composite, and that the energy absorbed should be the area under the graph of the strain-stress behaviour during an impact. Therefor I guess that the yield strength of a composite is very high in order for it to take the requiered energy.. But the biggest pro's for using that kind of material in a formula car is the weight and the flexibility in design..

What I dont know is the purpose of a honeycomb structure in between the composite layers and in what direction its placed. My interest in these questions derives from a project called formula student, where a team build a formula car during a year and then compete against other schools.

We've looked into differents solutions of energy absorbing koncepts. Aluminium honeycomb structures, composites (which been discussed and it seems to me its timeconsuming and requiers a lot of knowledge), and also different foamkoncepts...

[cupidstunt]

I know that a metall is less brittle then a composite, and that the energy absorbed should be the area under the graph of the strain-stress behaviour during an impact. Therefor I guess that the yield strength of a composite is very high in order for it to take the requiered energy.. But the biggest pro's for using that kind of material in a formula car is the weight and the flexibility in design..

What I dont know is the purpose of a honeycomb structure in between the composite layers and in what direction its placed. My interest in these questions derives from a project called formula student, where a team build a formula car during a year and then compete against other schools.

We've looked into differents solutions of energy absorbing koncepts. Aluminium honeycomb structures, composites (which been discussed and it seems to me its timeconsuming and requiers a lot of knowledge), and also different foamkoncepts...

Honeycombs in composites are used in order to increase the effective thickness of the material. This increases the bending stiffness, with a relatively modest gain in weight. The honeycomb itself provides relatively little of this stiffness, and is really just there to tightly bind the two separated layers together.

If you delaminate such a sandwich, then the honeycomb is very strongly fixed to the composite layers, but is itself quite insubstantial, almost like foil. I would therefore think that it's use in an impact stucture would be to increase it's stiffness, but not to absorb a significant part of the energy.

[Just_a_fan]

What I dont know is the purpose of a honeycomb structure in between the composite layers and in what direction its placed.

Think of a steel I beam. The composite layers are the top and bottom flanges, the honeycombe is the web. The purpose of the web in a beam is, basically, to keep the two flanges apart and thus maintain suitable lever arms.

When subjected to a load applied normally to the face, the face nearest the load is in compression, the further face in tension. The further the faces are apart the higher the load that can be sustained for a given amount of material in each face (subject to the web's ability to keep the faces apart).

A quick google brought up http://www.sussex.ac.uk/engineering/doc ... ture_6.pdf. The first page and a half give a simple overview of the this.

If you think of a lever (say a spanner/wrench for undoing wheel nuts). A short lever needs a large applied force (from your hand) to undo a nut. Make the lever longer and you need less applied froce from your hand. You never exceed your hand's ability to apply the load if you use a long enough lever. Similarly, if you put the faces of the beam far enough apart the same amount of material can sustain much more loads than when the faces are close together.

As for direction of placement, see http://en.wikipedia.org/wiki/Composite_honeycomb

Edit: spelling

[conni]

a lot of side impact structures are just rolled at an angle around a tube so that on inpact it concertinas and absorbs the impacts

conni

[polarboy]

As stated a nosebox is a carbon/honeycomb layup but its a very specalised layup,at the front where the tip fits you probaly have a pure carbon layup
The core in USF1 vid looks very simple ,to get the best results you can have the core getting thicker as it goes from the front to rear of the box you can also have your core in diffrent stiffness,s so again you can start soft on the front getting stiffer to the rear.As with a chassis where it has its squeeze test the nosebox will have section of the stiffest core in the area of the push off test
You alter your layup to give you decelaration within set figures (you could build a box so strong it would stop so suddenly it could pulp your driver internally an kill him) layup varies each year as the nose shape changes but there are things that are done year after year,just slightly diffrent each year

[skwdenyer]

To those who state they believe the honeycomb absorbs very little of the energy, that is not entirely correct. If the "through" axis of the honeycomb is parallel to the applied load, the honeycomb will compress and then buckle, followed by a controlled "accordion" crush - in effect, the buckling and folding mechanism will be repeated many times through the crush event, each time dissipating some energy.

The last time I saw one, an F1 nosecone was laid-up like a series of "russian dolls"; a cone of CFRP wrapped in honeycomb and then additional CFRP, and so on.

Some of the honeycomb along the sides will serve to increase the resistance to buckling of the cone's sides during longitudinal compression; all of it will absorb energy through the crushing mechanism outlined above (and also remembering that aluminium work hardens very rapidly, which can have a profound effect); some of it will increase resistance to bending.