Balanced and Symmetric Layups with PW Fabric
Balanced and Symmetric Layups with PW Fabric
(OP)
Do you need an even number of plies to achieve a balanced and symmetric laminate with plain weave fabric? Assuming plain weave fabric, would [0F/45F/0F] be considered unbalanced and unsymmetric?





RE: Balanced and Symmetric Layups with PW Fabric
RE: Balanced and Symmetric Layups with PW Fabric
Brian
www.espcomposites.com
RE: Balanced and Symmetric Layups with PW Fabric
I was struggling to prove this to myself with CLT using uni lamina property laminates of [0/90/+45/-45/90/0] vs. [0/90/+45/-45/-45/+45/90/0] trying to replicate 3 ply vs. 4 ply fabric laminates. But upon more useful "physics 101" I used the eLaminates spreadsheet by ESP and put some PW fabric properties from CMH-17 into it and checked out the A and B matrices. Thanks again for your help!
RE: Balanced and Symmetric Layups with PW Fabric
You can represent the plain weave fabric ply as a 2D orthotropic material in a state of plane stress, where E1=E2. Inputting this into a laminate program will show [B]=[0] and A16=A26=0.
Brian
www.espcomposites.com
RE: Balanced and Symmetric Layups with PW Fabric
RE: Balanced and Symmetric Layups with PW Fabric
Blakmax
RE: Balanced and Symmetric Layups with PW Fabric
Symmetric laminate is where [B]=[0] and in-plane/out-of-plane deformation is uncoupled.
Balanced laminate (typically when we just say "balanced" we mean w.r.t the in-plane deformation) = A16=A26=0 and shear-extension deformation is decoupled.
Flexurally balanced is where D16=D26=0 and bend-twist coupling does not exist. Also sometimes called an anti-symmetric laminate when unidirectional plies are used.
Regarding the "rules" to achieve these conditions, they are different for unidrectional plies and fabric plies. We often use undirecitonal plies and the "rules" are usually set up for that assumption, but those do not exactly work for fabrics. This can sometimes cause confusion and hence the reason for the original question.
Side note, you can not achieve a symmetric, balanced, flexurally balanced laminate when unidirectional plies are used (as you mentioned), but you can when plain weave fabric plies are used (for the same reason as stated in post 5). For symmetric and balanced laminates with uni-plies, where the layup is "homogenized", D16/D26 can often be reduced to insignificance (or nearly so).
Brian
www.espcomposites.com
RE: Balanced and Symmetric Layups with PW Fabric
Blakmax
RE: Balanced and Symmetric Layups with PW Fabric