Shin guards...help please

General Composites Discussions Composites Talk
#1

Hello Masters of the Composite Universe:

Well, I am still learning a lot from your great forum.

This time I have a project for my cousing, he is an amateur soccer player, and he would like to have some shin guards for him, custom made.

I am about to do the molds, there should be no major issues on this, I will take as a plug a pair of his favorite shin guars.

At this moment, I have a roll of sweet twill 2x2, 199 gsm, I am doubious about how many layers of this cf I should use.

On some products offered in the web, some fabricators mencions that they do not use any core materia, they use 100% cf. I think this is a good way to go.

I am considering maybe to use 6 layers of the mentioned cf, not pretty sure if this will be enough, and infuse as for first trial. I have use some vinylester resin for some infusion test, which I consider strong enough for this project.:wink:

Any recomendation will be greatly welcome.

Best Regards!

Antonio

#2

I would think you’d want to use a toughened epoxy to give the part more impact resistance.

#3

Kevin:

What brand of epoxy would you recomento to go for? I am located in Mexico, but most of my supplies I bouth them in the USA by mail.

Regards.

#4

I would highly recommend aramides instead of carbon. stiffness is of no concern, but impact resistance is critical. A direct hit on a carbon product can shatter it, turning it in a set of knifes…

#5

I was going to mention the chance of carbon shattering as well… serious chance of injury if that ever happened…

I was talking to my local composite supply shop about making CF motorcycle fairings, he mentioned the dangers of shattered carbon/glass and suggested adding a layer of aramid fabric. At least then you will not have pieces flying off. They had a sample piece in the shop, two layers of glass with Innegra in between (that’s just another brand of aramid, not as tough as Kevlar, but you can also cut it with normal scissors and grind/sand the finished part…). Anyway he was smashing this piece over the edge of a table, it had already seen some “testing” previously and there was no way this thing was breaking into pieces. Yes it was cracked and damaged - but still in one piece. You can get this type of aramid fairly cheaply. Or even a aramid/carbon hybrid?

You need to sandwich aramid between at least two other layers, I’m not sure if you should add additional aramid as the part thickness increases?

#6

I agree that aramid or Innegra would be a better choice since they have a lower density than carbon and have better impact properties.

FYI, Innegra is high modulus polypropylene not aramid.

#7

ok, thks, i will work on the mold and on get the innegra, i am thinking now on maybe 4 layers of innegra and one of cf for the top.

thanks, i appreciate your coments.

#8

The thing that stinks about Kevlar and Innegra is that you can get inter-laminar failure on parts that get impacted repetitively. The resin doesn’t bond to these materials as well as properly treated fiberglass or carbon. The solution is to use woven hybrids (glass-kevler or carbon-kevlar). Formula One floor boards are typically made from carbon-kevlar hybrids. The kevlar prevents the floor from shattering and puncture and the carbon in the weave prevents delamination due to it’s better interface with the resin.

#9

I tried to look for the innegra, I did not find an online seller on the web (I did not look a lot).

Do you have a suggested supplier for it in the US?

I think I will go with the hybrid, carbon & kevlar, but if I could get some innegra I would do some tests in order to see which could work the best.

#10

Thanks Infusible for that clarification - glad to get my facts straight!

wyowindworks - that makes sense. What about other hybrids? I have seen Carbon/Twaron on Easy Composites websites. I guess the main advantage is that they’d be easier to work with, if you don’t need the durability of kevlar.

I’m also just wondering about Carbon/Kevlar hybrid… I have seen conflicting information about working with Kevlar. Some say that you must trim the kevlar to end inside the part edge, otherwise you’ll have a fluffy edge that you can’t get rid of? Others seem to be able to trim their parts okay, but it seems like it’s a lot of work and they go through multiple blades just to trim one part?

#11

Does anybody knows if innegra woven is on sale on the US?

I found some pictures on the web, I liked the white & black pattern, anyway I will have as another option some kevlar & cf hybrid.

Thanks.

#12

Check with BGF Industries, they announced a partnership with Innegra Technologies back in May, 2012. You can also try Barrday.

They will probably not sell small quantities though. The easiest route is 100% aramid or carbon/aramid hybrid.

#13

I’ve purchased Innegra S from these guys: http://www.scenterprisesfiberglass.com/innegras.html

#14

This took more time than I had wish (family, lot of work on my primary job), but here are finally the shin guards, I started with infusión, but I get some briding and dry spots, and then I tries vacuum bagging and get much better results.

mold making

Infusión and result

Load test, I am a 100 kgf guy!

Vacuum baging and final part after polished

#15

Twaron® = Kevlar® = Aramide. Just other brand names from different manufacturers. (Akzo and Dupont)

#16

Looks like a nice result apolo607! Now I guess you’ll just add the foam back and ankle elastic and strap?

Cheers herman, glad to know that now.

#17

Forgot: There is also Technora, which is available in black and gold, and is also an aramide. However, after Teijin (producer of Technora) took over the Akzo aramide department, I do not know the status of Technora. It was nice stuff.