Composite preforms should be of high quality and reproducibility and require short production time. But building perfectly laid-up, complex 3D shapes with as little scrap as possible is an ongoing challenge. Several factors influence the production, potentially resulting in draping defects like wrinkling, folds or gaps, if a laminate is not designed properly. For automated lay-up systems, these defects can be efficiently prevented by digital laminate design. That’s why Cevotec’s ARTIST STUDIO uses a draping algorithm for exact patch placement visualization.

“To optimally reduce overlaps between patches while preventing the introduction of unplanned gaps into the laminate, ARTIST STUDIO software now uses an integrated draping algorithm.”, explains Herbert Weidinger, software and project engineer at Cevotec. “This eliminates the need for separate draping analyses and enables ARTIST STUDIO to deal even better with very strongly curved surfaces, especially with larger patch sizes.”

With traditional layer-based composites, when applying a fabric on a hemisphere, there always will be folds and wrinkles in certain areas. To a certain extent these folds and wrinkles can be prevented by adjusting the shear angle distribution, at the cost of deviating from the desired fiber orientation. With Fiber Patch Placement, draping effects usually don’t play a significant role since the patches for most applications are small compared to the surface shapes. However, when larger patches have to be applied, from a certain point on, the only thing that really helps is a draping algorithm.

With the kinematic draping, also known as geometric draping or fish-net algorithm, Weidinger and his colleagues accurately predict the contour of each individual patch inside a laminate. “Especially when patching lightweight structures for the aircraft industry, accuracy is of the utmost importance”, emphasizes Weidinger and continues with an example: when a lightweight application demands the complete coverage of a surface with a single layer of patches, the overlapping areas between patches have to be minimized to save weight, but at the same time, the introduction of gaps have to be prevented.

The FPP design module PATCH ARTIST precisely describes the position and shape of all patches in a laminate. A fast and efficient way to do this, for simple geometries, is to project a flat patch onto the surface. But for more challenging surfaces, e.g. strongly curved surfaces, projection is not exact enough and there will be deviations between the predicted and the actual patch shape. The reason for this is that the projection produces only an estimate of the actual shape and so the surface of the patch in the projection is slightly larger than in reality, if not on a flat surface. But even this tiny deviation can be fatal in some use cases. With ARTIST STUDIO’S integrated draping algorithm, these deviations are reliably avoided. Instead of projection, exact calculations are performed.

Easy to use and as accurate in its results as required, the draping algorithm definitely helps to improve composite part design and ensures producible parts with excellent mechanical properties and minimal weight.

About Cevotec:

Cevotec enables manufacturers to build complex fiber composites in high volume and quality – by smart process automation based on Fiber Patch Placement technology. With SAMBA Series, Cevotec offers a customizable fiber lay-up automation platform for challenging 3D geometries and multi-material laminates with complex fiber orientation. ARTIST STUDIO is the associated CAE software for generating patch-based fiber laminates and automated robot programming. Along with development services that include FE-based modeling and simulation, Cevotec offers the entire process chain from digital design to final fiber product.