Hi everyone, 

> Will I find a rather easy way of making a I beam, or is it more simple to just do 2 U beams that I glue together ?

The latter is easier, but it's a waste of material, because most of the material will be in the wrong location, strengthwise.

You are working with composites now, so other shapes that are difficult or even impossible with metals can be used.
Does the part really have to be shaped like an I beam? What about other shapes? E.g. a box structure?

XXXXXXXXXXXXX
XXXX          XXXX
      X          X
      X          X
XXXX          XXXX
XXXXXXXXXXXXX    (Picture is obviously sideweays, rotate by 90 degrees)

This can be made from 2 U shaped parts and 2 flat sheets glued together. Easier to manufacture and stronger than an I beam of the same weight.

> I saw tutorials on the internet where the guy puts his composites in the oven and some where he does not and I
> haven't yet figured out what the true difference is ?

Whether heat is necessary depends on 1. the resin used and 2. the required strength.
ALL resins benefit from elevated temperature curing, and some absolutely require it.
As a rule of thumb: resins with longer pot life benefit more from the heating than those with shorter pot life.
 
You don't need an industrial oven to do this, often you can get away with using a styrofoam box and a few lightbulbs, or a cardboard box and an electrical heater with fan.

> Can I avoid the infusion part (although I find it very cool) ?

Sure, hand layup still works fine. Vacuum bagging too.

My final advice, same I always give: start building the prototype with cheap glass.

Why make in 2 parts and glue together ? lay up your u sections then place together then laminate either  side of the side laminates then two pressure plates for the sides

Hi, 

I think f1rob pretty much means the same, maybe this:

XXXXXXXXXXXXX
XXXXXX  XXXXXX
           X X
           X X
XXXXXX  XXXXXX
XXXXXXXXXXXXX

2 U things glued together and then laminated on the outside and compressed with some plates.

> About the DIY oven, I'll start investigate but if you have any pictures, links or tips...

Thanks for reminding me, I have an oven project going on right now, might post a description as soon as it is presentable.
It involves an Arduino and a Raspberry Pi which logs temperature data, acts as a web server and displays temperature curves and controls the whole oven (PID, temperature ramp up and down) over the internet or your local network/WLAN with your smartphone, tablet computer, TV set, labtop etc. Cost for the whole controller will be around 100-150€, plus whatever oven is being used (*cough* ... old broken fridge or freezer *cough*), accuracy hopefully 1°C or better.
Ultimately I want to control an autoclave with it, but that's yet another project.

A real oven isn't necessary, you can improvise this. As I said, cardboard box and hairdryer will work, or a styrofoam box and a few lightbulbs, part wrapped in dark plastic and left in the sun, car parked in the sun in summer... be creative.

> i may be able to ask in the kitchen of my work. Do you know if there is any danger of curing carbon in a protection
> bag and cooking a dish afterwards ?

I wouldn't do it. Not only because of the resin vapours (which might be not that dangerous depending on what resin is used, others might disagree), but since you are using somebody else's oven and other people eating food prepared in it... better not.
Another reason is temperature accuracy. Kitchen ovens tend to be rather inaccurate and the temperature oscillates wildly, like +/-10°C. If you want to tighten them up you need to modify them.