Composite Airframe Design Stress stack up versus design stack up of plies 1

[Macm_020171]

New in the composite airframe design. I was given a stack up of plies from Stress analysis group based on sizing criteria. Stack up looks symmetric and balanced. But I was asked to validate from a design point of view optimizing weight and manufacturing constraints. What I'm supposed to do? Thank you.

Also I can I can see 2 plies transitioning from -45 to 45 (plain weave fabric) is there any difference for a fabric if it's + or -45 degrees?

 

[Sparweb]

What I'm supposed to do?

A matrix. Get out your school textbook.

+/- 45 degrees: it makes no practical difference.

 

[3DDave]

It would be best to ask the stress analysis group who should have provided the exact material specifications. You think it is plain weave but without that documentation in hand you have no assurance.

 

[SWComposites]

Macm -
- re weight, Stress could have already considered and optimized that. Maybe what you are supposed to do is total up the part weight and compare to requirements.
- re manufacturing, you need to discuss with the manufacturing engineers at the site that will build that part.
- don’t you have a supervisor or lead who csn (and should) answer these basic questions?

 

[rb1957]

+-45 ... you say "weave fabric" (as opposed to uni-directional tape).

your fabric has different E1 and E2, yes?

then +45 is different to -45, as +45 will have E1 on 45deg and E2 on -45; and -45 will have E1 on -45 and E2 on +45.

You are a designer I take it (not a stress analyst), so as a designer there is no weight impact. The impact would be in the amount of material required to create the different plies.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[SWComposites]

for PW fabric, essentially E1 = E2, so no difference in +45 and -45.

 

[SWComposites]

Actually, the other thing you need to do - these days Stress will give you ply stack in different zones in the FEM - A designer needs to figure out how to make continuous plies transition or line up between those zones.

 

[Macm_020171]

Sparweb, I don't know how a matrix could help me to optimize a layup in terms of design and manufacturing. Can you give me some hints? I think that last post from SWComposites s more aligned with what I need to do.

 

[rb1957]

I think Sparweb was talking as though you were a stress analyst. But I think you are a designer, as indicated by "I was given a stack up of plies from Stress analysis group" and your questions "was asked to validate from a design point of view optimizing weight and manufacturing constraints".

Ply orientation has no impact on weight, but there are some manufacturing questions that need to be considered.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[Ng2020]

Considerations:
How will you transitionfrom one layup to another across the part? Or is it constant layup?
Is it a sandwich panel?
Fastened joints? Do theae have different layup requirements from stress, compared to the acreage laminate?
Stacking sequence. Dont want lots of plies of same orientation grouped together, leads to edge peel/delam.
Any specific processing limitations fpr the material system eg max/min thickness, radii.
Allowables coverage for the proposed layup (stress consideration)?
Consider splice zones. How big is the part conpared to fabric. Where can/can't stress tolerate butt splicing.

Springback post cure. Tool shape: male/female?. Bagside/toolside surfaces, finish considerations for mating parts, aero smoothness. Sharp Radii - ply bridging, resin rich/ dry fibre zones.

How to prevent corrosion at cfrp:al fay surfaces.

Enviro protection. Weathering abrasion. Uv. Moisture ingress. Hail? Discrete source damage.

Repair?

Thickness. How many plies between each required debulk operation?

Edge of part tooling features.