Which is the best material for center plates for diy quadcopter. 

Glassfiber, Scrap PCB , Plastic  sheets , ply, Infact anything, that you can work with or is light weight and strong

best is carbon fiber

@bhanu - The BEST indeed is Carbon Fiber- It has more strength to weight ratio than any other material , But for a scratch builder or Hobbyist, this material is not that good due to it's availability, cost, and also the equipments needed to work with it
On Kiran's question he states he is DIYing thw quad - so he will be making his own frame - So  I suggested easily available cheap material - One can go for CF - if he has the budget and it is available

Sooraj he asked for best so the best is best without the options

He never mentioned cheap or free

Well I suggested some commonly available materials that are easy to work on , and purposefully avoided CF

 

Ok, thanks Sooraj and bhanu.
Got some thick plastic square plates.They weigh 65grams each. Need to use two of them for 450diy quad.Total plates weight-130grams .Is it fine or too heavy?

I can't judge whether or not that is heavy since i have not DIYed a frame. My Reptile 500 frame itself weighs around 500 grams totally. However, what really matters is whether your motors can lift your quad. Finish building the frame and weigh it. You can then estimate an AUW and choose a motor and prop combo based on that. Plastic is a good choice since CF is harder to work with.

Are you planning to replicate DJI F450 frame center plates and put 450 arms to it,
Then surely plastic is not the best material, Go for GF, Or another idea is use GF Copper clad sheets (Sheet used to make PCB), then you can also integrate a power distribution board as in the original DJI frame, If you don't know how, I can help

Looks I was wrong in saying plastic is a good choice. Glass fibre PCB sheets are easy to work and light and strong as well. You can easily get them cut and drilled at local hardware/ fabrication stores. I got the firewall for my FT Flyer made out of copper clad board at a nearby place and the guy did not even charge me. I just tipped him. He did the drilling with a screwdriver bit sharpened on a chop saw  . A PDB can be etched into it with ferric chloride (easily available online) though you have to be careful to ensure that the traces can handle the current. Using an online calculator and coating the traces with solder would help. You could always buy a ready made PDB or wiring harness instead.

I meant the switchboard type plastic.Its very hard and strong.

Switch board material is not plastic
It is hard yet is not light weight- and also is somewhat brittle.

So go for Copper clad sheets.

That board is used for making pcb's right?I used them for my last frame.They bend easily. How about aluminum?

We are not speaking of those normal hobby class clad sheets, Clad sheets for professional use are made of thick GF, they wont bent. Read this thread of mine, from reply#5 : http://www.rcindia.org/multirotors/custom-fpv-quadcopter-build/

My quads bottom plate is of such a PCB (It's hard, and light weight), If you want will send a pic.