Weighing carbon fibre preforms

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#1

Currently manufacturing flat panel CFRP parts. For our specific infusion technique, we have to calculate the exact quantity of resin which is to be injected into the dry carbon preform. To do this we weigh the preform, using this weight, we calculate a volume for the fibre and based on the 60%Vf principle we work out the volume of resin, and hence its weight. For this to be accurate, there are a number of important factors. One being how the preform is weighed and how accurate the scales are. Based on panels being approx. 10’ x 4’, any ideas on the best and most accurate way to weigh them?

Cheers

#2

besides rolling up the stack, or even each layer and measure each one?

really big scale.

or 4 scales with a platform the size of your preform. I think you just add the # on all scales to get total?

#3

well, the method being used now is a scale underneath either end of a sheet of metal. then add up the total of the 2 scales. this method isn’t giving consistant results.

Andrew

#4

This is why fabrics are listed with weight per sq yd.

36"x36" of 10oz fabric weighs … 10oz!

#5

That’s assuming you cut or measure the dimmensions perfectly. Then It takes a degree in math to figure out the area of odd shapes.

In general I think the process you chose has more control of the ratio of resin content than the operator. Especially for something with as little mechanisation as infusion.

#6

Mix up more than enough resin in a graduated container… after the infusion is done calculate how much resin it took. You only need to do this once or twice before you know the exact amount of resin to mix. Right? or are we saying with infusion it is possible to get too much resin into the laminate? I say infuse the panel to figure out how much it takes… using that graduated bucket or cups.

#7

TET is pretty darn on the money… if your using 100 ounces of cloth then mix up 110 ounces of resin… need extra for what fills the lines and bottom of the bucket so you don’t suck air into your laminate, obviously.

#8

*** Removed post because apparently it was useless. ***

#9

Again that works well with rectangles. What happens when you’re working with an oddly shaped charge cutting it out by hand? CAD and a CNC cutter would need to be used.

#10

The NCF has a nominal weight which it should be, but it is never spot on so theoretical calculation of the preform weight tends to be inaccurate, hence the reason why we weigh it. The NCF is manufactured to within certain tolerances so it is never one exact weight. We are manufacturing 10’ x 4’ panels up to 1.2" thick so theroetical calculation of weight is often quite a bit out.

Resin calculation isn’t as simple as it sounds when you have to take into account binder weight, stitching weight, resin in racetrack, resin left in ditribution mesh etc.

Im thinking hanging scales may be the most accurate way of weighing the preform.