What is Automated Preforming Technology?
For high performance composites the preforming of fabrics is an essential step in the manufacturing cycle. In this process dry fabrics are cut into shape of the part and different layers are stacked on each other. To avoid a relative movement of the plies binder is applied. The 2-dimensional layers are than draped into a 3-dimensional shape. In this draping step no relative movement of the fabrics is allowed since the properties are highly dependent on the fiber orientation and wrinkles and therefore must be avoided. The Automated Preforming Centre at the FPC is combining all these steps in one integrated machine allowing preforms to be manufactured in cycle times of the moulding step and on full industrial scale.
Key Research topics in the field of Preforming Technology
The process is very new and fundamental relationships between material, process and part design needs to be investigated. This includes the type of fabrics, the type of binders, the processing parameters and the mould design. For final part manufacturing the preforms are used in combination with the HP RTM. The development of this technology was automotive driven through their need for lightweight material. Mostly Tier 1, raw material suppliers and mould makers as well as automotive OEMs are interested in this technology as the main focus is high performance parts in medium volume applications. The automotive industry will benefit from it as weight savings that can be achieved through metal substitution and part integration. This Preforming Centre is the first of its kind in North America and globally the fifth installation of that kind of Preforming Centre.
What is Compression Molding Technology?
Compression Molding Technology offers an innovative way for manufacturing lightweight composite parts for medium to high production volumes. Sheet Molding Compound (SMC), Long Fiber Reinforced Theromplastics (LFT) and Resin Transfer Molding (RTM) are examples of material preparation processes that can be used with compression molding.
At the Fraunhofer Project Center @ Western, the compression molding research focuses on material and process development, molding of reinforcing structures (such as continuous fibers or metallic inserts) and the simulation of the flow behavior in the mould. Achieving Class-A surface qualities is also an active area of research in combination with the upstream processes SMC, LFT and RTM.
Compression Molding with Carbon Fibers
In addition to studying the incorporation of carbon fibers within the different manufacturing technologies into the polymeric matrices, compression molding also needs to investigated. Due to the differences in fiber diameter, fiber sizing and fiber architecture, the flow behavior of carbon fiber loaded materials is different from glass fiber reinforcement. Therefore, the compression molding cycle needs to be investigated and adapted towards these boundary conditions. Additional process features, such as vacuum assisted molding or in-mould coating, are also of interest.
What is Injection Moulding of Long Fiber Reinforced Thermoplastics
Injection moulding, as compression moulding, is a process for manufacturing of lightweight composite parts. At FPC, the 1600tons injection moulding unit is capable of moulding parts up to a size of automotive front end carriers. The unit is capable of using unreinforced granules, short fiber reinforced granules and long fiber granules. Additionally, a circulating hot air oven is integrated in the machine for pre-heating of thermoplastic tapes or organo-sheets. A robot loads the tapes and sheets in the oven and then transfers them to the mould. These inserts can be overmoulded with the suitable resin types. The plasticizing unit is also equipped with a MuCell unit for physical foaming and the clamping unit is capable of mould breathing for manufacturing of in-situ sandwich structures.
Key Research topics in the field of Injection Moulding
Three different fields of research will be addressed with this machine: resin formulation development, processing parameters investigations and mould and part design for especially local reinforcements and foaming at the same time. The combination of foaming and local reinforcements and the resulting in-situ manufactured sandwich structures allow the application in fields with high stiffness and high strength requirements. The interest can mostly be found in the automotive sector, on the OEM level, the Tier 1 and Tier 2, the mould makers as well as the machinery suppliers and the raw material suppliers. All steps in the value chain of manufacturing will be addressed. New rules for designing parts and moulds will be derived and know-how for the resin and fabric selection will be created. Additionally integration of functions and consolidation of part assemblies into integrated structures will targeted. This machinery set up at the FPC is the first of its kind in full industrial scale. The technology was introduced in fall 2013 and on intermediate scale only. With this shear edge equipment the FPC has a unique position for injection moulding of automotive parts.
What is Long-Fibre Reinforced Thermoplastics?
LFT is an established technology in the automobile industry using lightweight materials for semi-structural applications, having advantages such as: innovative materials, novel joining technologies, and attractive functional integration possibilities, as well as low density compared to metals. Further improvements in materials and production costs, will enable a continuation of the significant growth of LFT materials shown in the past few years.
For the past 10 years, the Fraunhofer ICT has carried out remarkable research and development work in the field of long- fibre reinforced thermoplastics such as local continuous fibre reinforcement. A strong focus has also been on the formulation and process development for direct LFT processing technologies, including in-line compounding (LFT-D-ILC). This accumulated experience and know-how are available at the Fraunhofer Project Center @ Western through its joint venture partnership with Fraunhofer ICT.
Key Research Topics in the Field of LFT-D-ILC Technology
What is Resin Transfer Molding?
Resin Transfer Molding includes high performance composite components with continuous fibre reinforcements based on textile structures made from glass, carbon and aramide fibres are finding increasing applications in the aeronautic and automobile industry. These innovative materials allow light-weight high performance structures to be created, as an alternative to conventional metal structures. The manufacturing of small number of components is carried out using RTM process.
The manufacturing for high performance composite components made from thermosetting matrices, such as epoxy and phenolic resins, is already established in the aeronautic industry, and also finds niche application in the automotive industry. The Fraunhofer ICT is carrying out intensive research to improve production and processing technology to create new fields of applications. Scientific objectives include the application of microwaves to increase the fluidity of the resin and improve the infiltration of the reinforcing fabric structures, and the microwave associated curing of the thermosetting resins (Cure on Demand).
A further innovative research topic at the Fraunhofer ICT is the material and process development for the manufacturing of components with in-situ polymerising thermoplastic matrix systems. The use of thermoplastic matrices for the production of continuous fibre reinforced composites have a number of advantages, including:
What is Thermoplastic Tape Laying?
Thermoplastic Tape Lying process is automated tape placement process for production of high-performance monolithic, shell-like components from UD tape. With this unit, the pre-impregnated tapes with unidirectional fiber reinforcement are placed in a 2D layup with automated set-up. Tape layers are connected with spot welding, and subsequently consolidated and thermoformed to more complex 3D shape. A particular advantage of this technology is rapid, precise, load-optimized tape laying with any orientation in the component. Profiled wall thickness can be achieved, and production waste can be minimized. The technology also offers the possibility of recycling, as well as the use of thermoplastic welding and joining processes.
New developmental strategies are required to adapt this specific processing of continuous-fiber-reinforced, semi-finished products to medium and high production volumes. Fraunhofer Project Center @ Western offers experience in the processing of these materials, including pre-impregnated woven fabrics and laminates, fiber mats and fiber roving structures.
It is also possible to combine the process with other thermoplastic processing methods such as LFT-D compression or injection molding. Here, continuous-fiber-reinforced laminates are transferred into the mold locally, or as two-dimensional carrier structures, and are combined with long- or short-fiber-reinforced material to create complex, functionalized components. Some examples of functionalization include ribs, clips and screw bosses. This approach to process combination, also known as tailored LFT and tailored injection molding, is one of our core topics, and combines the advantages of the different processes.
The demand for this process can be found in the field of automotive sector, aerospace and military and defense. OEM companies, Tier 1, mould makers and materials suppliers are interested in how to integrate thermoplastic tapes into parts for local reinforcements.
In this context replacement of existing metallic structures will be the outcome. New rules for designing parts and moulds will be derived and know-how for the resin and fabric selection will be created. Additionally, integration of functions and consolidation of part assemblies into integrated structures will be targeted.
What is Thermoset Sheet Moulding Compound?
The thermosetting fibre reinforced composites based on Sheet Moulding Compounds (SMC) enable lightweight solutions for applications where high mechanical, chemical and thermal stability is required. SMC components are becoming increasingly established in automobiles and utility vehicle applications. This is due to the fact they are associated with various advantages such as low density, high thermal and chemical stability, dimensional stability and the Class-A quality surface appearance.
Research activities at the Fraunhofer Project Center @ Western are targeted towards the development of SMC semi-finished products, processing technology and materials development. Goals include achieving Class-A surface appearance, lightweight SMC, tailored SMC, the use of reinforcing carbon fibres and incorporation of nanoparticles during processing. The newly developed materials and components can be evaluated by using available testing and characterisation technologies at the Fraunhofer Project Center @ Western.
Direct process for SMC
The direct process for SMC (D-SMC) enables continuous production of SMC-compounds. This innovative D-SMC one-step process eliminates the need of a several day maturation period necessary in conventional SMC process, and reduces the processing time from the raw material to the finished product, to a matter of just a few minutes.
As a consequence of the elimination of the intermediate step compared to conventional SMC, in D-SMC, each material formulation, including the fillers and reinforcing fibres, can be varied for the individual components during the ongoing process. Beside the reduction in the cycle times and costs, this also leads to a high degree of flexibility during component manufacturing.