clear plastic brittleness any way to make it stronger

Sorry, but no. You'll have to adjust the way you handle them.
Do you need a replacement canopy for the 190? What do you have? I am working on a 1/48 Tamiya dora and have a flat canopy I'm not going to use, if it will help.

It doesn't necessarily make them stronger, but I have found that coating clear parts with Future prior to cutting them from the sprue seems to reduce the tendency for cracking and spalling.

ACESES5

Why are clear parts so brittle

Generally speaking, clear styrene is more brittle than coloured styrene because the clear styrene does not contain any filler material (and perhaps plasticisers) which make it more resilient.

hkshooter: Thanks for the offer I had a spare in my parts box left from a hasagawa kit used it and thanks for info guys,I'll just have to be a little more gentle.             ACESES5

HI; I do believe you have stumbled into a problem most aircraft builders have had at one time or another.I don,t do that many, but, if its a very special (to me) a/c then when I buy it i go to the vendors list in FSM and buy the vacuformed replacement.These parts are made from a different plastic and are very flexible as well as very thin" SCALE THICKNESS" almost.Give it a try on your next one and I sure am glad you had a spare. tankerbuilder

tankerbuilder: Thanks I've wanting to try that next plane build I'll give it a try.             ACESES5                                               ON BENCH PANZER IV AUSF D "VORPANZER CYBER 1/35