How many have used carbon fiber tubs and for the rest of the tin work in a street-rae car any negetives

Carbon can go soft with a fire...depending on what resin is used.

carbon fiber will also conduct electricity and cause galvanic corrosion. so insulate it.

i have used it for building jet ski parts / hulls. it can be very strong if your layup is right, but it also never really loves impacts. it can crack, shatter or explode with a solid impact. Like a rock from the tire.... not saying it will, but be mindful.

100% of the load will go through the stiffest fiber until it fails, Kevlar carbon and glass could be layered and the carbon takes all of the stresses of the panel. Kevlar has a resistance to penetration and the glass would be a fill layer.

i used kevlar once in a marine application... it was in the middle of glass and carbon, it got wet after some damaged and turned into a sponge... it holds water. was a issue for me, but not for your idea.

I've seen some 5 layer Carbon Fiber parts aircraft made with one thin layer of Kevalar in the middle take a bunch of abuse and hold it form

My entire car is carbon fiber, no corrosion, or electrical issues here. Carbon tubs use a liner on the tire side to keep from chipping/breaking.

Well that's kinda correct, I think what the point is here, CF is not very flexible, so any load induced goes first to the stiffest oriented CF of the layup, there is some load sharing as CF is not perfectly stiff, nothing is, but when that fiber's strand is loaded beyond 100%, it fractures, and the next stiffest fiber assumes most of the load, and so on, until total failure if the load remains. This is one on the dowsides of CF, it that its possible to design/layup an item where an internal CF strand is the highest loaded component, it will fracture when overloaded, and there is no normal outside viewable indication of such, until ultimate sudden failure, and not even currently xray detectable pre failure I believe, Different fibers that have as one of their attributes elasticity or stretch, share their loads with adjacent fibers, and the item deforms significantly before yielding. Kevlar is as mentioned ideal to resist penetration, less stiff then CF, and helps to keep the fractured CF pieces together to assist in a future repair when the CF fractures. I include a kelvar layer in almost all my CF layups. Do not under estimate regardless the ultimate strength and properties of Kevlar.

Concerning another comment on another reply on this topic, the temp/heat robustness of a layup is usually dependent on the type and quality of binder, resin or epoxy, not the reinforcement used.