Calculate thickness

Talk Composites - The Forum for Advanced Composites

Back

Calculate thickness

Author	Message
Abraham George	Abraham George posted 5 Years Ago Topic Details
Group: Forum Members Posts: 5, Visits: 7	I would like to know if there is any particular method to know abt the thickness of the composite before curing. How do you calculate the amt of materials for getting a required thickness in Resin Infusion ?
	Reply Like 1
Hanaldo	Hanaldo posted 5 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	When using woven materials under vacuum compaction, the fibre weight per layer corresponds very closely to the cured thickness. For example, a single layer of 200g woven carbon will provide roughly 0.2mm thickness, a 450g woven carbon will provide roughly 0.5mm thickness, a 650g carbon will provide roughly 0.7mm thickness, etc.
	Reply Like 2
Lester Populaire	L Lester Populaire posted 5 Years Ago Post Details
L Group: Forum Members Posts: 311, Visits: 13K	+x Hanaldo - 8/21/2019 6:10:03 AM When using woven materials under vacuum compaction, the fibre weight per layer corresponds very closely to the cured thickness. For example, a single layer of 200g woven carbon will provide roughly 0.2mm thickness, a 450g woven carbon will provide roughly 0.5mm thickness, a 650g carbon will provide roughly 0.7mm thickness, etc. Only accurate for carbon tho. Glass is going to be thinner at the same surface weight, natural fibers are going to be thicker for a given surface weight.
	Reply Like 1
Hanaldo	Hanaldo posted 5 Years Ago Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Yeh correct, it depends on the fibre densities. However it does still provide a useful indication.
	Reply Like 1
Abraham George	Abraham George posted 5 Years Ago Post Details
Group: Forum Members Posts: 5, Visits: 7	So if I want to make a 3 mm thick plate with E-glass reinforcement...what is the approx no of fibre layers we should use? Our is a research proj on vartm based composites so the plate size is of limited dimensions and there is no mould also.
	Reply Like 1
Greybridge	G Greybridge posted 5 Years Ago HOT Post Details
G Group: Forum Members Posts: 3, Visits: 50	+x Abraham George - 8/21/2019 1:21:56 PM So if I want to make a 3 mm thick plate with E-glass reinforcement...what is the approx no of fibre layers we should use? Our is a research proj on vartm based composites so the plate size is of limited dimensions and there is no mould also. The only way to know for sure is to do a few test runs with a known layer count and a consistent lean out pressure. DO NOT leave your infusion under full vac to lean out. Your resin will boil and and your part will be garbage. Pull resin at full vac until it enters the vent tube, then reduce vac to a lean out pressure appropriate to your tests (go slow so air doesn't push back into your part). Without knowing what your end goal is I can't say exactly what the lean out pressure should be but I wouldn't go more than -15hg. That will get you below the condensation point of your resin and reduce your void volumes by half but still be enough vac to evacuate resin and give you some amount of compaction. Which brings me back to the point, the amount of compaction will affect your per layer thickness. There's a few ways to control this but the most accurate is to weigh your layup before and during infusion and evacuate resin until you hit a specific resin/fabric ratio. Once you have control over your r/f you can predict your mm/layer and thus predict your ultimate part thickness.
	Reply Like 2
Lester Populaire	L Lester Populaire posted 5 Years Ago Post Details
L Group: Forum Members Posts: 311, Visits: 13K	Or just measure thickness of fabric stack with some calipers and reasonable clamping force. Will get you close. Double check with resin density and fibre density and expected volume fraction. Will get you close as well.
	Reply Like 1
Abraham George	Abraham George posted 5 Years Ago Post Details
Group: Forum Members Posts: 5, Visits: 7	+x Greybridge - 8/21/2019 3:29:25 PM +x Abraham George - 8/21/2019 1:21:56 PM So if I want to make a 3 mm thick plate with E-glass reinforcement...what is the approx no of fibre layers we should use? Our is a research proj on vartm based composites so the plate size is of limited dimensions and there is no mould also. The only way to know for sure is to do a few test runs with a known layer count and a consistent lean out pressure. DO NOT leave your infusion under full vac to lean out. Your resin will boil and and your part will be garbage. Pull resin at full vac until it enters the vent tube, then reduce vac to a lean out pressure appropriate to your tests (go slow so air doesn't push back into your part). Without knowing what your end goal is I can't say exactly what the lean out pressure should be but I wouldn't go more than -15hg. That will get you below the condensation point of your resin and reduce your void volumes by half but still be enough vac to evacuate resin and give you some amount of compaction. Which brings me back to the point, the amount of compaction will affect your per layer thickness. There's a few ways to control this but the most accurate is to weigh your layup before and during infusion and evacuate resin until you hit a specific resin/fabric ratio. Once you have control over your r/f you can predict your mm/layer and thus predict your ultimate part thickness. What do you mean by goal?
	Reply Like 1
Abraham George	Abraham George posted 5 Years Ago Post Details
Group: Forum Members Posts: 5, Visits: 7	+x Lester Populaire - 8/21/2019 4:19:13 PM Or just measure thickness of fabric stack with some calipers and reasonable clamping force. Will get you close. Double check with resin density and fibre density and expected volume fraction. Will get you close as well. Stack which includes mesh, peel ply....right?
	Reply Like 1
Lester Populaire	L Lester Populaire posted 5 Years Ago Post Details
L Group: Forum Members Posts: 311, Visits: 13K	+x Abraham George - 8/21/2019 5:10:23 PM +x Lester Populaire - 8/21/2019 4:19:13 PM Or just measure thickness of fabric stack with some calipers and reasonable clamping force. Will get you close. Double check with resin density and fibre density and expected volume fraction. Will get you close as well. Stack which includes mesh, peel ply....right? Well no, if you aim for 3mm of glass i personally would use about 3mm of glass...
	Reply Like 1