Tag Archives: Infusion

Raw material suppliers outlook a good future for dry composite materials

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Key structural composite components are being manufactured with dry preforms and resin infusion, replacing in many cases the use of prepreg materials for parts manufacturing. In this sense, raw material suppliers play a key role when developing the newest materials to meet the aerospace sector strict quality requirements. What are their thoughts regarding the use of infusion process for the aerospace industry?
We have had a short interview with some experts in the area. Henri Girardy, from Hexcel and Sven Blank, from Saertex have shared their overview about this subject with us.
Thank you Henry and Sven!

Saertex HExcel

1. What are the primary benefits that Infusion offers in aerospace applications, compared with long established prepreg and autoclave curing processes commonly used today? What applications appear to be most promising?

Sven Blank (SB): Multiple layers/orientations in a single fabric can facilitate higher deposition rates resulting in savings of both time and money. Moreover, the use of NCF can eliminate some, if not all debulking processes. In addition, most infusion materials can be stored at ambient temperatures and have extended shelf life (1-2 years) when compared to prepregs. This way, the material handling is simpler and there is no need to chart out time or storage temperature and it is not required to wait until materials come to ambient temperature.
There is no risk of foreign materials to be present in laminates due to use of release paper, etc.

Henry Girardy (HG): Key benefits are cost and production rates. Cost savings have been demonstrated in part design, function integration, less assembly time, and potentially fewer finishing operations.

2. Automation such as AFP has played an important role increasing quality, increasing rate and reducing cost of parts made with prepreg. Are there opportunities to do the same with Infusion processes?

SB: Parts with complicated geometries, thick parts or parts with large surface areas are requiring higher deposition rates. Therefore automated dry fabric deposition technology could be a good option to enhance increasing rate and quality. On the other hand, narrow dry tapes could be used as localized reinforcement of NCF lay ups.

GH: We strongly think that automation of the dry preform is a key success of factor for aerospace structures made by OOA technologies. OEMs and Tier 1s are looking forward for eliminating the costly autoclave curing process.Moreover, as we see it, one of the main reasons why dry materials do not fully meet the mechanical performance requirements for primary structure, is the lack of automation in lay-up process. Therefore, there is a need to automate the process.

3. It is a commonly held perception that infused materials do not provide as good mechanical properties as prepreg/autoclave materials.
a. If true, this means that an Infused part will have a weight penalty?.
b. If false, what can be done to improve the understanding of these materials?

SB: Infused materials could also provide good mechanical properties, but there is some work to be done to improve the understanding of the materials. Such as…
-Educating customers regarding the advantages of NCF and infusion.
-Expand marketing of  infusion materials into aerospace applications
-Publish/present data from controlled experiments comparing infused and prepreg laminates.

GH: The new materials, such as our HiTape® fabric, enables really good properties in vacuum infused parts. Parts up to 30mm thick with a 58 to 60% fibre volume content can be achieved. Infused materials will play a key an important role for next generation aircraft, due to the fact that apart from weight, costs will also drive the material and technology choice.

JEC Europe 2014: innovative products, aimed at dry preform manufacturing and infusion

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The most innovative products aimed at dry preform manufacturing and infusion where shown in JEC Europe 2014,  the most important trade fair of composites industry that took place in Paris between the 11th and 13th of March. The fair keeps showing a great level as long as it refers to expositors and visitor numbers, as for the quality and quantity of products and innovations that were presented.

The big possibilities that this material offers are already being exploited in all kind of industries and the biggest issue is now the increase of productivity and the improvement of production costs.
In this post we  have highlighted some innovative products, aimed at dry preforming and infusion,  that drew the attention of the DRY COMPOSITES team.

MATERIAL HANDLING SOLUTIONS
Schmalz showed its solutions for the composites industries, with its range of vacuum and needle grippers for carbon and glas fiber fabrics handling. According to them, they will be launching  briefly electrically operated grippers, which will offer great benefits to those proffesionals who want to avoid the costly compressed air.

Also with the interesting quality of the flexibility to addapt to the desired geometry, Fraunhofer IPT presente two new solutions. An-Octopus Kinematic gripper which is adapted easily to the deposition point, as well asflexible shaped electrostatic grippers.

Schmalz´s and Fraunhfoer IPT´s grippers

Schmalz´s and Fraunhfoer IPT´s grippers

FLEXIBLE DEPOSITION HEADS

AFPT presented its multimaterial, head winner of the JEC innovation Award 2014 wich is able to process thermoplast tapes, duroplast prepregs and dry fiver rovings. The head was originally developed by Fraunhoffer IPT. The head is constructed in a modular way and it can be adapted to different fiber materials, such as glass and carbon fibers, as well as various matrix materials on the same equipment, using lasers.

AFPT´s flexible deposition head

AFPT´s flexible deposition head

COMPLETE PROUDUCTION CELLS
Companies such as Dieffenbacher or Fives, presented its fully automated cell for composites parts manufacturing. By acquiring the Relay machinery, expertise and intellectual property rights of Fiberforge, Dieffenbacher is investing in the automated tape placement technology, both dry material placement and also adding a key technology to its product portfolio in the growing market for thermoplastic structural components for lightweight design. Hi Pressure Resin Transfer Molding machinery by Kraus Maffei was also presented in the exhibition

Dieffenbacher´s cell for composites parts manufacturing

Dieffenbacher´s automated cell for composites parts manufacturing

AUTOMATED WIND BLADE MANUFACTURING SOLUTIONS: MAPRETEC PROJECT
An interesting German government funded project was presented at the Show. Saertex, Areva and Bremen University have developed together a new solution for the automated wind blades manufacturing. It consists of a new and innovative approach based on the two-dimensional automated layup of single NCF layers to a multiple stack followed by the forming of the final contour into a 3D preform.

Mapretec´s project

Mapretec´s project for automated wind blade manufacturing

SOLUTIONS FOR FRPP COMPONENTS PRODUCTION WITHOUT RELEASE AGENTS
Fraunhofer IFAM presented 0,3 micrometer thick plasma-polymer release layer that leaves no residues of release agents on either the component or the mold.

Fraunhofer IFAM´s thick plasma-polymer

Fraunhofer IFAM´s thick plasma-polymer

DRAPABILITY CHARATERIZATION SYSTEMS
Textechno presented DRAPETEST, a new automatic drapability tester, that has won the JEC Innovation Award in 2014. The solution to automatically characterize drapability and the formation of defects during draping and forming. the tester combines the measurement of the force, which is required for forming, with an optical analysis of small-scale defects such as gaps and loops by means of image analysis. An optional triangulation sensor can determine large-scale defects such as wrinkles

Textechno´s drapability characterization system

Textechno´s drapability characterization system

 

-Advancements in dry reinforcements for aerospace infusion process

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While in some previous posts we focused on talking about different automated processes for dry material deposition (ADMP, Pick-and-place and DAFP), this post deals with information about dry reinforcements aimed at aerospace infusion process and automation.

  • Why dry reinforcements?

Dry reinforcements offer significant advantages versus prepreg materials that have been traditionally used in the aerospace sector. They present several benefits, thanks to their low prices, their long shelf life, reduction in inventory costs, potential to increase parts integration and  potential to avoid the costly autoclave curing process.

The growth of the resin infusion process in the aerospace industry (as  can bee seen in the image above and our -Aerospace Looking to Dry Fiber/Infused Composites post) is increasing the need to adapt dry materials to the aerospace and new technologies requirements.

Infused Aerospace parts

Infused Aerospace parts  in Boeing 787, A380, A400, Bombardier C-Series and IRKUT MS-21

  • What is driving innovation in dry reinforcements?

Although there is still much to do in the area, material suppliers offer more and more products oriented to automated dry material deposition processes. Focusing our attention on dry reinforcements, the main research and developments in the area are aimed at:

Binders which are compatible with the resin to be infused and ease the manageability of the fiber during the material deposition.

Thin layers of thermoplastic veils to facilitate the flow of resin infusion and provide the final part with a greater toughness.

Dry carbon fibers that provide the strength and stiffness in a unique or multiple directions (unidirectional or multiaxial reinforcements). Different forms of dry carbon fabrics can be used to this end. NCF (Non crimp fabrics) are the most used fabrics nowadays, whereas the woven fabrics have also improved their properties in order to ensure the achievement of the required qualities.

The combination of the dry reinforcements with the proper resin is essential in order to manufacture a good quality part. Great developments are being carried out in this area.

  • Unidirectional tapes or Non Crimp Fabrics: Different choices for automation.

Unidirectional tapes up to 1″ offer high flexibility in terms of the geometries they can achieve. Automated process, such as the Dry Automated Fiber Placement (DAFP), use these tapes to produce preforms that will be infused during further stages. The productivity they can reach is low so far.

Wider Non Crimp Fabrics (NCF) can be used with the automated process such as ADMP and Pick-and-Place. The improvements in these materials and related automated deposition technologies could revolutionize the composites sector because of the great production rates they can accomplish.

You can have an overview of these different automated process in our post Making a Preform – How Can I Count the Ways?

  • What are the most common dry material forms used by the latest aerospace programmes?

It is known that the Saertex group supplies high-performance multiaxial and unidirectional NCFs for the manufacturing of the Bombardier´s C-Series and Learjet 85´s major primary structures.

Meanwhile, AeroComposit has qualified Hexcel´s OoA Hi-Tape material to produce Irkut Ms-21´s wings and wingboxes, whereas Spirit AeroSystems has also used the same material to form a skin of an engine nacelle outer fan cowl. Aircraft structures made with HiTape are reported to demonstrate mechanical properties as high as those found in parts  made with the latest generation primary structure prepregs.

Hexcel´s OoA HiTape

Hexcel´s OoA dry HiTape

Finally, it is worth mentioning that Cytec offers a material with equivalent properties, being applied also in the Irkut  MS-21. Both tapes (Hexcel´s and Cytec´s) will be used to manufacture the aircraft structures automatically within a DAFP machine.

-Resin Infusion techniques in the aerospace industry

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Many methods have been developed to perform the resin infusion in the aerospace industry, once the dry preforms are created manually or automatically. These processes are identified by different names and acronyms, which can lead to some confusion. Here is a description of some of the more widely known infusion methods.

SCRIMP (Seemann Composites Resin Infusion Molding Process) is one of the earliest patented infusion methods. It is used for many marine and Wind blade applications, but was also licensed by some aerospace firms. It relies upon the use of a flow or “distribution media” with high permeability between the layup and vacuum bag to rapidly and evenly distribute resin laterally across the part.

SCRIMP Schematic

SCRIMP Schematic (link)

VARTM (Vacuum Assisted Resin Transfer Molding) is the name of the process used by Lockheed Martin that is similar to SCRIMP, but does not use a flow media. The entire fuselage of the AGM 159 JASSM missile is made using VARTM.

JASSM made with VARTM

JASSM made with VARTM (link)

CAPRI (Controlled Atmospheric Pressure Resin Infusion) was patented by Boeing and is said to reduce thickness variation and result in fiber volumes and mechanical properties equivalent to prepreg/autoclave materials. First it uses vacuum debulking cycles on the dry preform to reduce compressed thickness prior to infusion. During infusion, the resin supply is held at partial vacuum, which assists in degassing the bulk resin but also reduces the pressure differential driving resin into the preform.

CAPRI Schematic

CAPRI Schematic (link)

VAP (Vacuum Assisted Process) was patented by EADS and used in parts like the A380 Aft Pressure Bulkhead and the massive A400 Cargo Door. VAP features a gas permeable membrane placed over the infused layup, which helps to evacuate trapped air and volatiles in the infused layup prior to cure. By letting gases through the membrane (but not the resin) VAP is said to achieve lower voids and higher, more controlled fiber volume for better laminate quality.

VAP membrane

VAP membrane (link)

RTI (Resin Transfer Infusion) is a Bombardier patented process used to produce the wing skins of its CSeries aircraft. Infusion of resin into the preform is performed with vacuum pressure only. However, the mold is located in an unpressurized  autoclave during the infusion step. After the preform is fully infused, the autoclave is pressurized and heated to perform cure. This makes it easier to achieve high laminate quality because positive cure pressure (>14 psi) helps prevent void formation from entrapped air and volatiles. It has the drawback that a suitable size autoclave is still requited. All other methods cited above are true Out of Autoclave processes.

C-Series wing made with RTI

C-Series wing made with RTI (link)

There are also other acronyms for similar processes, which can create a kind of “alphabet soup” confusion about infusion.

The important thing to remember is that many different users have had success making a wide range of parts (some very large and critical) using infusion processes.

-Pros and Cons of Automated Preform manufacturing methods

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In our last post we described three methods to automate dry fiber Preform manufacturing: Pick-and-Place, Dry Automated Fiber placement and Automated Dry Material Placement.

Pick-and-Place (PNP) – Ply patterns are cut on a Table Cutter, “picked up” and then transferred or “placed” into the mold.

Dry Automated Fiber Placement (DAFP) – Similar to prepreg AFP, where bands of narrow unidirectional tapes are placed into the mold, except that the tape is dry (not impregnated). A small amount of binder holds the tapes in place as they are placed under heat and pressure.

Automated Dry Material Placement (ADMP) – Fabric rolls are cut into Ply patterns and placed into the mold, all in one operation and one machine pass over the mold.

PNP, DAFP and ADMP preform manufacturing methods

PNP, DAFP and ADMP preform manufacturing methods

Each of these automation methods provides advantages and disadvantages, as presented below.

Preforming Methods – Pros and Cons

Preforming Methods – Pros and Cons

PNP has been used to produce preforms for some time, and directly mimics the way many prepreg, RTM and infused parts are made today. The industry is comfortable with designing, producing and inspecting CNC cut ply patterns, whether from prepreg or dry fabric forms. Flat pattern shapes of any complexity can be accommodated (internal windows, cutouts, etc.) Instead of manually placing plies in the mold, with PNP this operation is performed by a machine, therefore the complexity of the layup (mold contour, folded flanges, etc) is more limited. Both woven and noncrimp fabric (NCF) styles provide good mechanical properties as well as excellent permeability for complete resin wetout and infusion. A drawback to PNP is that more floor space is needed for both the Table Cutter and the PNP transfer mechanism. If cut plies are not laid directly in the mold (i.e. are stored in kits before layup), PNP requires more ply handling, which makes it more difficult to manage fabric distortion and placement accuracy.

The design practices, machinery and manufacturing approach with DAFP are very similar to prepreg AFP. This familiarity or aerospace “pedigree” makes DAFP attractive because it is a less disruptive process change where AFP equipment is already in use. Other benefits of DAFP include very good properties achieved with unidirectional fiber and the lowest material scrap rate, since each tow is dropped or added exactly as needed. This feature also means that complex patterns can be produced, though there remain limitations associated with minimum cut-and-add length and edge crenulation. The use of individual tapes allows DAFP to conform to complex shapes. The drawback of DAFP is similar to that of AFP – in practice, actual productivity (pounds deposited per hour, i.e. the floor-to-floor or C rate) is relatively low.  The time required to manually inspect every placed tape against the defined drawing often far exceeds the time the machine is actually placing material, and this is another factor in low throughput.

ADMP’s value proposition is that it can achieve very high productivity due to wider materials (than DAFP tow bands), multilayer materials (such as NCF) and pre-made layup schedules provided in the fabric form itself. For example, to produce a balanced, symmetric quasi-isotropic layup only requires 2 passes of an ADMP machine (using a four layer [0/45/-45/90] NCF fabric placed back-to-back) but requires 8 passes of an DAFP machine to produce a [0/45/-45/90]s layup from uni dry tape. Like PNP, the textile forms used in ADMP have very good through thickness infusion properties, but ADMP textile forms do not provide mechanical properties as high as unidirectional tape used in DAFP. The mold contours and ply pattern geometry suitable for ADMP is somewhat more limited than for other methods, and the method has yet to be proven for use in aerospace applications.

So there are many factors and tradeoffs to consider. Nor are PNP, DAFP and ADMP the only ways to automate the Preforming process. Other methods like stitching, 2D and 3D braiding, 3D weaving and others are also being used.  Ultimately the choice of Preforming method, when it comes to automation, depends on the specifics needs of the application and the customer.