I agree with Warren and Fred, placing the fibers in different directions is more of a  F1 and Aerospace thing where they need every little bit of strength and where cost isn't an issue. Placing Kevlar within the layers will hold it together, even using woven roving also

seriously, i appreciate the participation and discussion --


Scott

CarbonFiberCreations

I made monocoque for my bike before I made it with carbon,i made it out offe glass tested till failure,then when I made it out off carbon gave myself a safe margin,the one thing about carbon is when it let's go eg. Failure you get. No notice,where by using glass gave me notice,this seem's to me to be because off the stiffness off carbon,to use this material to its upmost having engineering skills would help,but a bit off common sense helps,also when I make a part I look at where the weight is being loaded asess stress area's and decide on material weight's and application.

thanks warren and fred for the input
this is way better and more useful than a politics forum ! LOL

scott

CarbonFiberCreations

Dear Rambling Man!

If you put one layer of Kevlar in the middle of your stack the shattered carbon is going no where! It would be like sfety glass when shattered. Kevlar will never rip and so hold the carbon.

Fred

i did make that point regarding vehicle bonnet safety design in another thread, as they are designed to react a certain way to pedestrian safety

Some good composite theory in those links.

However, in practice that level of design is usually overkill for most DIY projects. The extra cost of the waste and wider fabric needed for doing a 45 degree layer for a relatively small increase in stiffness usually isnt worth it when, for example, a foam core will achieve even better stiffness for a quarter of the cost of that additional carbon layer.

Sure for more specialised applications then its fine to use all the advanced principles - that is what they are for, to achieve the best strength etc.

Not withstanding that, it is useful to understand how and why your part behaves in the way it does.

An interesting point touched on is splintering and people getting hurt in a crash.  Depending on where you live and the jurisdictions applying to you, that could be a legal minefield.  Modified cars are a grey area in law for many countries, especially when it comes to modifying "safety related" componants.

Now in most definitions you'd be hard pushed to consider most bodywork as "safety related" componants however in our increasingly "risk averse" (read it "cotton wool" if your older like me) society then things like pedestrian safety are taking a greater and greater impact on car design legislation to the extent that many new cars designs are quite heavily influenced by it, eg lower further back engine, higher bonnet line, pedestrian airbags, pedestrian crumple zone panels etc etc etc.

Now personally i think its going too far, if we pander to safety too much we will be driving around in blocks of soft foam or further still cars will be banned full stop for being dangerous......

Why not just teach people to look before they cross the road and follow the highway code when driving? oh yeah we do teach people these things but they are often too stupid or too arrogant to follow them - hence avoidable crashes.

But thats just my view of it in europe where often legislation and burocracy seems to be put in place instead of people using some common sense....

You may have different views or be forced to subscribe to the safety culture more than I am.  

You can lesson the chances of splintering etc by adding an aramid or diolen based fabric in your layup.  The panel may be mashed beyond recognition, but it will remain largely intact with significantly reduced splintering.

Beyond simple principles like that, you are entering into the realms of having your parts crash tested to see if they are at least as good as the OEM parts.  That is an incredibly expensive and drawn out process beyond most of our means.


So that leaves us with having to make a choice as what is acceptable to us either personally or in a legal sense.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

well done !

CarbonFiberCreations

nice writting, 

thanks dudes! ya know, i think even one layer offset at 45 degrees probably would make a huge difference in what most of us make.
but things like a kayak...yeah i think i'd want that to be bomb proof. if it were to sink, get you soaked, or even fill up and not sink, your life would be endangered for sure.
i guess in a couple years i ll know a better answer LOL

scott

CarbonFiberCreations