Automating sandwich structures with Fiber Patch Placement

High-precision, repeatable lay-up for complex multi-material components

Author: Florian Lenz, Technical Director / Publish date 18.12.2025

Fiber Patch Placement (FPP) is uniquely positioned to automate the lay-up of complex sandwich structures. Especially placement of the skins and, where required, the adhesive layers on the core is in the core capabilites of this advanced lay-up technology. For the placement of sandwich cores, a proprietary gripper was developed and can be used for further process development. Combined with a high-resolution vision system for monitoring material quality and safeguarding placement precision, these options for a fully automated lay-up process make FPP a distinct solution for high-quality, repeatable sandwich manufacturing.

Figure 1 and 2: Complex lay-up operation of adhesive and skin patches  on a sandwich sub-structure panel.

Automated skin preforming on complex geometries

For the skin preform, FPP delivers a repeatable, high-quality lay-up even on demanding geometric features. Applications such as steep edge panels demonstrate that FPP can reliably place patches on complex shapes while maintaining a high laminate quality. Finite-size patches limit draping effects and angle deviations, resulting in more stable fiber orientations across the part. At the same time, FPP enables good initial compaction of the laminate, which allows to reduce or omit intermediate debulking steps in the process. The overall process is monitored by an advanced vision control system that not only checks raw material quality before placement, but also corrects eventual patch offsets on the fly to guarantee placement precision with a tolerance of ±2mm. This combination of precise placement and robust compaction is a unique capability of FPP technology.

Automated adhesive placement with defined overlap strategies

The second key element in sandwich part manufacturing is placement of the adhesive layer between skin and core. FPP supports automated adhesive placement for a wide variety of materials, provided that the adhesive is suitably reinforced for automatic feeding and cutting. To ensure consistent processing, the system can condition adhesive patches through an external heating field. This thermal control helps to prepare the adhesive for reliable pick-and-place operations. Crucially, adhesive patches can be placed with a defined overlap or no-overlap strategy, depending on the application requirements. With a “defined overlap” approach, FPP can also support electrical insulation of metallic honeycomb core structures through controlled adhesive coverage and overlap management.

Figure 3 and 4: Automated adhesive placement on a legacy aerospace sandwich panel

Automated sandwich core placement

Beyond the skin and adhesives, we also addressed the automated placement of sandwich cores by investigating different options on demonstrator parts. For honeycomb cores, a proprietary gripper design was developed to enable reliable handling and placement of these delicate structures. Foam cores, up to a certain material dependent size, can be picked and placed using the standard Cevotec patch gripper, allowing manufacturers to cover a broad range of sandwich core materials within the same process environment. The capability to automatically position cores complements the technology stack for a fully automated sandwich lay-up

Figure 5: Honeycomb core handling with Cevotec’s geometry-adaptable, proprietary gripper

How FPP supports production rate increase in aerospace

Several developments in the aerospace industry are driving the need for higher automation levels, also for sandwich panels and other complex secondary structures:

• Production rate increases for commercial aircraft
• Ongoing cost pressure
• An ageing workforce leading to labor shortages of composite technicans

Existing automation technologies such as AFP face challenges when it comes to complex geometries and functional requirements, for example defined overlaps for electrical insulation on metallic cores. To date, no automation technology has demonstrated full automation of the entire sandwich part lay-up – from skin to core to adhesive. FPP technology closes this gap.

FPP offers several unique advantages for sandwich structures:

• True multi-material handling in one machine:    
  FPP can lay-up reinforced prepreg, adhesive and core material within a single system.
• Automation of challenging geometries:  
  Geometries that are not applicable for automation with other lay-up processes (e.g. AFP) can be addressed with FPP’s patch-based approach.
• Automate legacy parts:      
  With advanced placement features like Post Placement Push In, FPP can work with non-optimized legacy tooling. This enables economical retrofits for automation in ongoing aircraft programs.

Industry Impact

Due to the quality deviations inherent in manual lay-up operations, NDT (non-destructive testing) is performed on every unit produced. Out-of-spec parts have to be reworked or even scrapped late in the manufacturing process, leading to avoidable waste and excessive cost.

The FPP process, on the other hand, is implemented with robotic systems that accurately collect and monitor a wealth of data in real time. To ensure that key part characteristics are achieved in every production run, process- and application-specific key process parameters (KPP) are defined, tested and validated pre-production. If KPP are in spec during production, individual NDT can typcially be omitted, as the validated KPP translate into achieved part characteristics. This significantly reduces the cost & time for final quality control and increases factory output. These savings are in addition to the cost & time benefits achieved by integrating skin, adhesive and core placement into one automated workflow.

In conclusion, FPP technology enables a significant reduction of manual labor and associated costs while guaranteeing repeatable quality by robotic high-precision lay-up, also for legacy parts / toolings. This translates into noteable production rate increases at lower unit costs.