Has anyone tried using polystyrene as a strengthening rib core with prepreg? Normal packing Polystyrene that is. I was thinking of using a semicircle shaped rib going along the edge of a component that needs to be very light, and I’ve got loads of Polystyrene about.
I´m afraid it is not the best material to combine temperature + pressure… Why don´t you use any hollow (half) pipe for your rib, as thin PVC or similar ?
you can even make your hollow (half)tube rib from carbón and it’ll contribute to structure. I mean: the complete half-tube (rib + sencondary laminate) will be reinforcing and it will be hollow.
The lightest.
(in my opinión)
Polystyrene will collapse under prolonged vacuum and that will happen without heat.
For solid foam core with prepreg you a need a proper PVC foam like Divinycell or Acrylic foam like corecell or Rohacell.
1-4 lb density EPS is Used in surfboards all the time.
However often sandwiched with a thin layer of structural foam as follows
glass
divinycell or corecell
glass
EPS
Glass
1/8"divinyscell
glass
With a sandwhich layer it provides some structure to prevent the upper sheet from collapsing when loading the X-Y oriented fibers in the Z direction. at a lighter weight. then other materials but is not an ideal core unless the load can be distributed over a large area.
Vacuum pressures >20inHG will crush it. and temperatures need to be kept reasonable. ~60 ish C not sure what your autoclave is hitting
As a reference 1lb eps with 1 layer of 6 oz fiberglass, you’ll put thumb prints handling it. with 12 oz of fiberglass you’ll put heal dents standing on it. with 18 oz you’ll put heel dents jumping lightly on. it.