riff_raff wrote:....marcush...
cycle times are indeed the limiting factor preventing more widespread use of carbon composites in automobiles. You might imagine that modern CNC tape laying machines would reduce cycle times. But just the opposite is usually true with parts made from pre-preg materials. Having several workers manually putting down pre-preg materials in a tool is still faster than a single CNC tape laying machine doing the same job.
Of course, a CNC tape laying machine that cures-in-place a thermoplastic resin matrix as it goes would be much faster, since there would be no cure cycle required. Not to mention the fact that thermoplastic resins are far stronger than epoxy or polyester.
I'm sure it won't be long until we see F1 tubs being made using CNC tape laying machines and cure-in-place thermoplastic resin matrices.
this whole thread and this post in particular are filled with so much incorrect information, i finally had to post to counter some of it.
the speed of automated tape laying and winding compared to manual layup depends on the part. Large cyclindrical and flat parts can be more effectively laid up automatically. parts with many intricate and small curves are best done by hand. it's possible to combine both approaches in a single part, using manual layin of the intricate/small radius areas with flat areas done by machine.
consolidating thermoplastic matrix composites in situ is very tricky for several reasons.
the laying head has to both apply pressure to consolidate the layer and carry the heating unit/cooling roller head. getting these to follow complex shapes with 'small' radii limits the radius and width of the head and thus the laydown rate. a good candiadate for thermoplastic in situ consolidation would be something like a torpedo hull or a long C section spar.
the strength of the common thermoplastic resins depend on the degree of their cured crystallininty. this, in turn, depends on the cooling rate from the melted condition. the rolling laydown head thus must travel at a very controlled rate. to get porosity comparable to thermosets, the rolling head is limited in its laydown speed.
this slower head laydown can make the thermoplastic total fabrication time be
longer than a thermoset part that is put into an a cure cycle.
powdered thermoplastic prepregs have yet to show any advantage in cost.
the current high performance thermoset resins have more than adequate strength and toughness.
it's already possible to get automotive parts -such as trunk liners- in and out of a mold in several minutes. these are usually dry, shaped, chopped- fiber glass preforms that are resin transfer infused in a mold and cured in the same mold. these typcially do not offer any weight savings because of the thickness of the required preforms. you couldn't use this for a high performance application. truck liners and boat hulls yes. an f1 chassis, no.
another of the drawbacks to the use of composite auto chassis is liability: it's much more difficult to detect accident damage with a composite chassis. (the same holds true for aircraft primary structure.)
because of the low volume and compound curves in an f1 car, i doubt that they'll ever justify automated production.
non-autoclave cures -including double vacuum chambers (NORVACCS), rtm, vacuum bagging in ovens and at room temperature, press molding, etc., have been around for decades. an autoclave cure isn't that detrimental in an f1 project.
