yet another Dave
well actually it does big time. at the beginning of the cycle at room temp the vacuum is on the inside of the bag to keep the work still and held against the mould. the autoclave is basically a big pressure cooker, so as temperature increases pressure inside the vessel does too and eventually the pressure pushing on the outside of the bag is greater than the vacuum inside, so at this point the vac line is vented to atmosphere and it continues on pressure alone. during the cycle temp and pressure can reach 220c and 7bar.Actually an autoclave is just the heat bit and not the vacumn. You tend to vacumn and then cure with heat afterwards. Few autoclaves have built in vacumns but they are specialist at curing resins that need the the vacumn, the pressure though is equal within the autoclave and has no bearing on mold pressure.
this depends on what youre going to put in it of course, an autoclave works on pre-impregnated cloth and would be wasted on lick and stick wet lay ups. if youre using an ordinary epoxy or polyester resin then you would help it with a little warmth but its keeping the humidity down thats more important, resins are hygroscopic and absorb moisture from the air. too warm would make the resin too runny and it would vac out leaving the work dry, too hot and you risk an exotherm which you dont want. your airing cupboard would be ideal.
100psi doesnt sound a lot but the autoclave we got at work is big enough for hercules radomes, you can stand up in it and if it burst bits of us would be found some miles away.
you can get good results with a simple vac bag on carbon but always use a bag, the fibres are stiff and wont lay on to eachother very well if they are not held down and you could end up with an air filled resin rich thing that is weaker and weighs more than the original.