Carbon Fiber roof actually just a PLASTIC roof, that's reinforced with CF?

[PKL]

I watched this video weeks ago when it was first posted. Pretty cool.

At the time either it wasn't, or I didn't notice that the video was called:

"Carbon Fiber Reinforced Plastic"

I was an English major in college, and if this statement is correct, it would lead the reader to believe that the majority is plastic, with CF as "reinforcement".

So we are clear, I am not bashing the CF roof, or trying to start an argument of any kind.

I am just curious... Why is it called Carbon Fiber Reinforced Plastic?

Also, based on very little, what do you all think about the CF roof in relation to Lucifer_M3's crash? I'm not saying a steel roof would have changed ANYTHING, but in the few pictures, the carbon fiber roof just looks like it could snap in half so easily. (based on completely unscientific viewing of a small photo)



ANYHOO, discussion....

[dexx]

Dear god... Carbon Fiber is plastic. The carbon by itself doesn't have any strength.. Not anymore than a sheet of raw fiber glass has.

[Locksmythe]

More accurately, it doesn't have any structure. It is essentially cloth, after all. Just really strong!

[PKL]

Thanks

So how about the "integrity" of a plastic roof in a crash???

[M3Dreams]

Originally Posted by Locksmythe

More accurately, it doesn't have any structure. It is essentially cloth, after all. Just really strong!

Very true, CF is a specially weaved cloth layered with special resin. The weave and the resin together give the strength while being ultralight.

[mmmpowered]

In reference to the picture above and all other similar crashes, I don't believe a metal roof vs. carbon fiber would have made an ounce of difference.

A metal roof is simply a thin skin (1/16"?) and once it's torn, buckled, etc, there is no strength remaining anyway. I would assume the structural components under either skin are nearly identical. Along with the rest of the chassis, that is where strength in a serious accident comes from.

Cars are designed to crumple upon impact of a relatively large object. A high speed side impact with something that is not a relatively large object, a tree in this case, does not provide enough surface area for the components to crumple as designed. It has nothing to do with the material of the roof skin.

I'm would also guess BMW modeled many times and crashed many real cars to determine putting production cars on the road with carbon fiber roofs would not be a liability for the company.

My .02

[JCtx]

The roof skin is purely cosmetic. But I still don't think this car is particularly strong structurally. I'm not going to sell it as a result of those pictures, but I wonder if a Porsche or Audi (or even a Vette) would have broken in half .

[ES_TRADER]

Originally Posted by Locksmythe

More accurately, it doesn't have any structure. It is essentially cloth, after all. Just really strong!

Is the roof basically the same as my carbon leather trim but just laminated all glossy then?

[kaykay]

Here go study:

http://en.wikipedia.org/wiki/Carbon_...forced_polymer

[Stainless 45]

I have also wondered about the strength of carbon fiber. We all know it looks cool, and is light, but how strong is it? As strong as steel of the same thickness? Or fiberglass? Any mechanical engineers out there care to weigh in?

[kaykay]

Originally Posted by richpuer

Is the roof basically the same as my carbon leather trim but just laminated all glossy then?

No, LOL.

[BMWBoss]

Originally Posted by elp_jc

The roof skin is purely cosmetic. But I still don't think this car is particularly strong structurally. I'm not going to sell it as a result of those pictures, but I wonder if a Porsche or Audi (or even a Vette) would have broken in half .

No matter what kind of car you're driving, it is not immune to the laws of physics. A speeding moving object + a solid structure without motion = DISASTER!!! This applies to BMW, Audi, Merc, or Hyundai.

[Bosna]

Originally Posted by BMWBoss

No matter what kind of car you're driving, it is not immune to the laws of physics. A speeding moving object + a solid structure without motion = DISASTER!!! This applies to BMW, Audi, Merc, or Hyundai.

Practicing physicist at your service. QFT!

[OC3]

I would think most, if not all, vehicle designs and their ability to withstand crash testings are heavily geared towards frontal or rear impacts - i.e. along the longitudinal axis of the vehicle. That M3 being split into latitudinal halves clearly indicates that.

Even then, on a high speed frontal crash, if a vehicle didn't have the front bumper and engine & engine bay to absorb the impact (i.e. vehicale impacted right where the firewall and the A-pillar are at), I would think the car could split longitudinally in half too.

The CF roof isn't designed for strength. If it was, there wouldn't be a need for a roll cage. CF roof is more to save weight.

Anyhow, in Lucifer_M3's crash, even steel roof'd M3 would split in half.

[Crazy Bimmer]

Originally Posted by elp_jc

The roof skin is purely cosmetic. But I still don't think this car is particularly strong structurally. I'm not going to sell it as a result of those pictures, but I wonder if a Porsche or Audi (or even a Vette) would have broken in half .

I really dont mean to flame but are you the type who tends to worry a lot? Its just something I notice from your posts. You seem to always think the worse of things when it comes to the M3.

Anywho, there are pictures of benz and audi split in half on the internet as well. Like mentioned, law of physics plays a big role.

Just google it and pics of any make pops up.

[dexx]

Originally Posted by Crazy Bimmer

I really dont mean to flame but are you the type who tends to worry a lot? Its just something I notice from your posts. You seem to always think the worse of things when it comes to the M3.

Anywho, there are pictures of benz and audi split in half on the internet as well. Like mentioned, law of physics plays a big role.

Just google it and pics of any make pops up.

Buy a volvo

/thread

[Crazy Bimmer]

I dont think in general roof panels are made to be that strong. I think the brace under the panel is what absorbes most of the impact if rolled over.

Lets not forget the Vette.

Although i think chevy sent out a recall for this to include stronger glue.

[UNNATRAL]

all carbon fibre is is they take fibre from bread, and mix it with cigarette smoke in a laboratory, and that combination shits out a cf roof. I read that in a scientific journal published at harvard. very true....

[Dok Henz]

Note: In no way is this post meant to criticize the events surrounding Lucifer_M3's tragic death, nor do I mean any disrespect to his family and friends by its posting.

As TX asked in a post in another thread:

I really want to know what sort of speed was obtained to result in this damage to the car meeting with a tree. Usually I see them wrapped around the tree, but never split in half like this. How fast do you have to go to cut a car in half?

Here are my "paper napkin" calculations based on Newtonian mechanics. Take them with a grain of salt, as I'm no physicist... so if you find the calculations or assumptions incorrect, I'll be happy to recant my post.

My assumptions & math:

• Premise 1: the part of the car that struck the tree went from entry velocity (X) to zero nearly instantaneously
• Premise 2: assume the entire mass (M) of the car as acting on that small bit of area to calculate the energy suffered on that area (an admittedly large assumption, avoiding complex calculations of torque and lever forces on the exterior portion of the car as the front and back "scissor" together)
• From non-relativistic mechanics: e=(1/2)*mv^2
• mass of e92 M3 w/CF roof and male passenger of average weight = 3900 lbs (1772 kg)

Based on the assumptions, hitting a fixed object at 150 kph (~90mph) would release about 150 megajoules of energy, or the equivalent of about 80 pounds of TNT; hitting it at 200 kph (~120 mph) would release about 150 pounds of TNT energy.

Since 10 pounds of TNT is roughly equivalent to 7.5 pounds of C-4, and it takes approximately 8-10 pounds of C4 to demolish an 8-inch square steel beam, one can see how 8-15 times that much energy could easily destroy a car... or rip it in half (if the charge was placed in the proper location and aligned with the most-effective blast orientation).

So, with regards to the question posed by the OP, I seriously doubt that a thin sheet of carbon fiber reinforced plastic - or any of the underlying metallic structural elements - could have remained intact after being exposed to so much energy.

My $0.02.

My condolences to Lucifer_M3's friends and family.

Dok

[3XTR3M3]

Originally Posted by dexx

Dear god... Carbon Fiber is plastic. The carbon by itself doesn't have any strength.. Not anymore than a sheet of raw fiber glass has.

At first I thought you were writing a letter to god

[Fuzzz]

I visited the Pagani factory not too long ago. They showed and spoke at lenght of the different techniques and materials used (in an all carbon car) to tune the carbon material to have e correct properties.

In the rear bulkhead and chassis they use layers of ballistic Kevlar mixed in with the carbon to make it extra strong to protect in case of an accident. Body panels are normal carbon.

My point is just like everything there are different ways to do things in order to get the right properties. The m3 roof has no structural purpose (carbon or steel) so why stress to make it strong.

[kaykay]

Carbon fiber is stronger than steel when pulled (known as tensile strength).

However, CF is weaker than steel when we talk about compressible strength (such as a major impact in the case of the crash here).