Representing multi-layer composite materials in SW

[laukejas]

Hi, I wonder if anyone has any experience with this. For example, suppose you need to design a composite part that is comprised of a different material stack "sandwich", for example:

Paint
Primer
220gsm carbon cloth
380gsm carbon cloth
220gsm carbon cloth
Foam
220gsm carbon cloth
380gsm carbon cloth
220gsm carbon cloth
Primer
Paint

And these materials need to be represented physically in the 3D model. Here's why:

1. Accurate thickness representation needed to tolerance the core and molds, especially when the stack (number of composite layers) differs in different locations of the part for strength/weight optimization;
2. Accurate weight estimations;
3. Accurate estimations of material usage;
4. Planning the layup and overlaps between composite layers;
5. Getting flat patterns for cutting composite cloth;
6. Estimating resin, primer and paint usage, as well as their added thickness, which can often become significant and impact final tolerances.

Now I'm aware that typically none of this is done in CAD and is basically eye-balled on the shop floor, but that also leads to lots of waste, dimensional inaccuracies, unpredictable final weights, difficulties in estimating material usage, etc.

So I'm wondering if there are any reasonable ways to represent such stackups in SW. I am aware that Simulation Premium has composite definitions, but these are only used for simulation, and cannot be used for BOM, weight, flat patterns, etc.

The way I currently do it, is building the shape of the model, and then adding the stackup either inside-out or outside-in with Surface Offset + Thicken, or Shell with Shell Outward enabled, and then assign different materials to different layers. However, this comes with many problems, such as:
1. Significantly increased rebuild times;
2. Issues with shelling/offsetting complex geometries due to minimum radius of curvature or similar errors;
3. It's just a lot of work.

Alternatively, sometimes I don't model (some of) these layers at all, but use equations to derive weight and material usage (especially for stuff like paint) by measuring surface area of the part. However, this doesn't solve the thickness/tolerancing and flat pattern concerns.

I know that SW is not really intended for this, and some of you might think what I'm doing here is unnecessary, but even with my crude methods it does really pay off when these numbers really matter. But perhaps someone found a better, more SW-friendly way of representing multi-layers material stacks?

[DanPihlaja]

I have been thinking on this off and on all day.

And I am not sure if there is a better way than you are already doing it.

I mean, you can make copies of the original parts, scale up/down, and then use the cavity feature to cut it out of the previous part. But that uses a percentage instead of an accurate offset.

The only way that I could see to make this faster would be to create a set of templates with all of the offsets defined by global variables.

Then, you can just use the template and update the offsets by modifying the global variables.

But it won't fix the minimum curvature errors. Not will it be faster processing.

Sorry mate.

[SPerman]

It looks like NX has an add-on for this purpose.

NX Fibersim

[jcapriotti]

Laminate Tools has SolidWorks support. No idea on cost or functionality.....can't imagine its cheap.

https://www.anaglyph.co.uk/

[Petertha]

I can kind of visualize what you are doing because I have a bit of (amateur) experience in this area where gram counting & strength is a big deal. But not fully comprehending the goals or maybe accuracy expectations behind the end result. SW accurately computes surface areas of a 3D parts. So you could determine area of the entire shape, call it part A. Or any number of reduced smaller area reinforcement layers where you dictate the corresponding boundaries from the master shape (parts B,C,D..). You already know the gsm values for your various sandwich cloth & core constituents, so isn't it just a spreadsheet calculation for each element & sum them up: (calculated m2 * spec gsm = grams weight). For wet layups there are rules of thumb for resin:cloth ratios. Pre-pregs are I think are more controlled & predictable.

I do know that other factors come into play. Particularly wet-on-wet you can get fiber nestling based on weave vs weight vs fiber orientation where both thickness & weight computes differently as a sandwich than single layer basis. Total thickness is similarly influenced by vacuum bagging parameters vs infusion, peel ply, its permeability specs. Hand layup has the most variation. Cores have different exposed porosity patterns & potentialy permeability as they must take on minimum resin volume for proper adhesion. So collectively, I'm no expert but I think making dedicated coupon layups of appropriate size, replicating the target layup sequence is worth doing or maybe even required. Maybe this was already done for strength purposes anyways? This may include post or pre painting both from weight & material usage standpoint. The coupons would tell you not only meaningful metrics to apply to your model area weight estimation but statistically how much variation between coupons.

I would think paint & primer is easy to estimate on a surface basis but a bit trickier on a physical usage basis without some real world tests. I bet if you measure the paint used on a 1m2 sphere it will be different than a 1m2 flat sheet just based on hand eye, overlap, distance, overspray etc. even by experienced technicians. Often primers are alternately tinted to give the technician feedback because primer density is high. That's why white airplanes always weigh more LOL.

I love composites. Just curious are you able to say what you are working on?

[laukejas]

It looks like NX has an add-on for this purpose.

NX Fibersim

That looks pretty close to what I need. Wish there was something like it for SW...

Laminate Tools has SolidWorks support. No idea on cost or functionality.....can't imagine its cheap.

That looks pretty well thought-out, although from that video (and some more googling) it seems that it doesn't actually add all that composite info (thickness, weights, etc.) back into SW, it only uses geometry from SW to generate the layup in that external program. Otherwise the definition of layers looks pretty interesting. Makes me think if I should write my own SW add-in for this...

I can kind of visualize what you are doing because I have a bit of (amateur) experience in this area where gram counting & strength is a big deal. But not fully comprehending the goals or maybe accuracy expectations behind the end result. SW accurately computes surface areas of a 3D parts. So you could determine area of the entire shape, call it part A. Or any number of reduced smaller area reinforcement layers where you dictate the corresponding boundaries from the master shape (parts B,C,D..). You already know the gsm values for your various sandwich cloth & core constituents, so isn't it just a spreadsheet calculation for each element & sum them up: (calculated m2 * spec gsm = grams weight). For wet layups there are rules of thumb for resin:cloth ratios. Pre-pregs are I think are more controlled & predictable.

I do know that other factors come into play. Particularly wet-on-wet you can get fiber nestling based on weave vs weight vs fiber orientation where both thickness & weight computes differently as a sandwich than single layer basis. Total thickness is similarly influenced by vacuum bagging parameters vs infusion, peel ply, its permeability specs. Hand layup has the most variation. Cores have different exposed porosity patterns & potentialy permeability as they must take on minimum resin volume for proper adhesion. So collectively, I'm no expert but I think making dedicated coupon layups of appropriate size, replicating the target layup sequence is worth doing or maybe even required. Maybe this was already done for strength purposes anyways? This may include post or pre painting both from weight & material usage standpoint. The coupons would tell you not only meaningful metrics to apply to your model area weight estimation but statistically how much variation between coupons.

I would think paint & primer is easy to estimate on a surface basis but a bit trickier on a physical usage basis without some real world tests. I bet if you measure the paint used on a 1m2 sphere it will be different than a 1m2 flat sheet just based on hand eye, overlap, distance, overspray etc. even by experienced technicians. Often primers are alternately tinted to give the technician feedback because primer density is high. That's why white airplanes always weigh more LOL.

I love composites. Just curious are you able to say what you are working on?

Yeah, I currently do mass/coverage/material usage calculations in a spreadsheet, using surface areas measured in SW (selection sets + sensors). But it's an ugly way to do it, not very parametric, requires overriding masses to get accurate assembly mass in SW with these composite components present, and still doesn't solve the issue of thickness/clearances.

I do my composites in a somewhat less traditional way: I 3D print the parts that I need, seal them with epoxy, and then reinforce them with fiberglass/carbon fiber, typically wet layup or infusion. You can think of the 3D print as a permanent male mold / core. The downside of this method is poor surface finish, requiring a bit of sanding and sealing, but it is enormously useful for one-off parts and prototypes, because it doesn't require making big and expensive molds that would be used just once and then thrown out. That also makes it more environment friendly. The resulting parts are very light, comparable to similar sandwich constructions made with foam (3D printed core has very similar mechanical properties to foam at the same density).

However, since the composite layers are built up on top of the 3D print, part has to be designed with all faces offset inwards by some amount (which is very different from scaling), so that the final part is exactly of the right dimensions. This becomes important when several parts made with this technique are assembled inside one another, and need to have very specific clearances between them. Below are a few screenshot from one of my current designs that shows such an arrangement:

Of course, this method of manufacturing isn't very tolerance-tight compared to molding, with many variables affecting the final dimensions (infusion VS wet layup, vacuuming, amount of resin, sanding/filling, etc.), but number and thicknesses of composite layers plays the largest role, and certainly needs to be accounted for.

I am currently finalizing the design of a small sailing boat made entirely with this technique, serving as an experiment/proof of concept for low-cost composite part manufacturing, with the aim of making lightweight and strong designs for amateurs and makers with limited budget and tooling. Current BOM for the boat I'm designing (4.5m long, 35kg) stands at around 1400€ (including consumables), which is approximately around 1/3 of the price of what it would take to build something like this with traditional molding, and around 1/10 of the price of similar-sized production composite boats in the market. It is my personal project as a maker, I don't have plans to commercialize it, like I said, the goal is to prove this technique and make it accessible for others. So far, the experiments turned out beautifully. If you search my previous posts, you can find some screenshots of that boat design if you're into such things


Which I hope explains the need of modelling these layers in SW, so that I can properly size the 3D printed core, adjusted for the number and thickness of layers, which might be different in different places of the part (for example most areas need 3 layers, but some might need up to 7). Planning it out in SW and getting flat patterns would greatly help to further bring down the manufacturing costs through minimizing off-cuts. Also, since this project is extremely weight-critical, and optimizing that weight is one of the main goals, having SW calculate these numbers on the fly is immensely helpful. That does mean, however, that even primer and paint needs to be taken into account.