Stefan Carosella

Universität Stuttgart · Institute of Aircraft Design

Gaps, fibre misalignment and foreign objects in dry fibre tape layups are detrimental towards the final mechanical properties of carbon fibre composite parts. Eddy current sensors can be used to inspect layups for the named defects. In comparison to optical inspection methods, eddy current measurements are capable of inspecting not only the top lay...

Graphene and its related materials are increasingly applied in fiber-reinforced polymers to tailor their material properties for high performance composites. Yet, the use of graphene derivatives that underwent a plasma functionalization process is not well understood. This study uses 1.50 wt.% of unfunctionalized (rGO) or plasma-treated reduced gra...

Preforming processes can be used for automated manufacturing of fiber reinforced polymers. Different technologies are used for processing of dry textile fabrics into 2D or 3D preforms. Due to missing tack of dry fabrics, auxiliary binder systems are used for fixation of the fabrics onto a substrate material and in order to achieve sufficient adhesi...

This paper deals with spread carbon fibre tows fixed by epoxy-based reactive binder that can be used in two-dimensional dry fibre placement (DFP) layups, which show freely selectable fibre orientation of each tow and layer structure. In a second step, the DFP preforms can be draped into a three-dimensional preform, here the bending stiffness has a...

Dry fibers or fabrics do not possess an inherent tack, when compared to prepreg materials. In order to fixate dry fiber fabrics onto tooling geometries, auxiliary binder systems are necessary. These tackifying agents vary in terms of chemical composition and reactivity, processing parameters and appearance. One key aspect for most automated fiber p...

The incorporation of graphene materials can further improve the thermal and mechanical properties of composites. Yet, the use of graphene derivatives that were functionalized using plasma treatment is relatively unexplored. This study evaluates the change of the thermal and dynamic mechanical properties of nanocomposites and graphene-enhanced carbo...

A suitable functionalization of graphene and its derivatives can further enhance the material properties of nanocomposites. In contrast to chemical functionalization methods that have been extensively researched, functionalization by plasma treatment is relatively unexplored. In this work, we compare the mechanical, thermal and electrical character...

Within the dry fibre placement (DFP) process, spread and pre-bindered carbon fibre rovings are automatically processed into dry textile preforms using 2-D and 3-D laying systems. The aim was to automate existing hand lay-up processes, reducing the complexity, increasing ro-bustness, and facilitating the handling of the DFP technology. Process relia...

This paper deals with spread carbon fibre tows with epoxy-based thermoplastic binder that can be used in two-dimensional dry fibre placement (DFP) layups, which show freely selectable fibre orientation of each tow and layer structure. In a second step the DFP preforms can be draped into a three-dimensional preform, here the friction has a significa...

This study evaluates the effect of plasma surface functionalization of reduced graphene oxide particles on the processing characteristics and homogeneity of dispersion of a bisphenol A‐(epichlorhydrin) epoxy matrix and amine‐based hardener with varying weight fractions from 0.00 to 1.50 wt%. It was observed that amine‐functionalized reduced graphen...

Our research aims to develop a shear forming envelope for the preforming of textiles, a critical step in the manufacture of fibre-reinforced composite materials. This paper demonstrates the progress towards this aim by conducting picture frame tests to empirically determine the locking angle of non-crimp fabrics with different fibre orientations. W...

Under normal conditions, the cross-sections of reinforced concrete in classic skeleton construction systems are often only partially loaded. This contributes to non-sustainable construction solutions due to an excess of material use. Novel cross-disciplinary workflows linking architects, engineers, material scientists and manufacturers could o�er a...

Fiber Reinforced Polymers (FRPs) are increasingly popular building materials, mainly because of their high strength to weight ratio. Despite these beneficial properties, these composites are often fabricated in standardized mass production. This research aims to eliminate costly molds in order to simplify the fabrication and allow for a higher degr...

This paper presents the application of printed strain sensors during the characterization of textile forming mechanisms. Using the example of trellis shearing, these sensors are applied to a fabric and shearing is performed in a picture-frame based shearing test rig. As the textile shears, opposite corners of the cruciform specimen start to move ap...

The Advanced Ply Placement is a novel technology for automated fiber layup, based on unidirectional fabrics. Recent research activities have been working on the placement of dry reinforcement fabrics. Due to the absence of tack, auxiliary binder systems are necessary for layer adhesion. These auxiliaries can be divided into reactive and non-reactiv...

This study evaluates the effect of a plasma treatment of graphene particles to produce a graphene material with an amine-functionalized surface to aid the dispersion process and the integration of these nanoinclusions into a polymeric matrix. The powder samples were characterized with regard to their chemical composition, morphology, level of defec...

Kurzfassung: Mit dem Advanced Ply Placement (APP) wird eine neue Fertigungstechnologie für faserverstärkte Kunststoffe vorgestellt. Das APP schließt dabei die Lücke zwischen etablierten Fertigungsverfahren (Automated Fibre Placement (AFP) und Automated Tape Laying (ATL)). Aufgrund der Kombination von segmentierten Greifern und einer formadaptiven A...

The present study deals with a novel binder activation approach for automated dry fibre placement. Via application of an electrical current within carbon fibre tows, ohmic heating is used for activation of binder systems. The working principle of intrinsic fibre heating is demonstrated within two prototype devices: A handheld tape laying device for...

This paper investigates the application of sensors on carbon fibre textiles for the purpose of textile characterisation and draping process optimisation. The objective is to analyse a textile’s condition during the draping operation and actively manipulate boundary conditions in order to create better preform qualities. Various realisations of text...

The present study deals with the development of a highly flexible unit for the spreading of various reinforcement fibres and the subsequent application of adaptable binder systems. This concept gives highest flexibility in fibre and binder combinations at low investment and minimal machine dimensions. This new technology-Flexible UD-Tailor Device (...

Breaking down the cost structure of state-of-the-art CFRP part shows that a major share of the costs is caused by labor and equipment as well as process energy consumption.Therefore, the main goal of the EU funded FP7 project LOWFLIP (Low Cost Flexible Integrated Composite Process) has been the reduction of these costs by introducing new technologi...

A successful application of braiding technology for the manufacturing of an industrial product is shown on the example of a carbon fiber-reinforced plastic (CFRP) manipulator. Due to its lightweight design, the CFRP system offers highly ergonomic advantages for the worker compared to the previously available steel version. In the course of the brai...

The properties of fiber reinforced materials are depending on the fiber direction. During draping processes - which are necessary to form complex structures - the fiber direction and therefore the resulting properties of the final part are changing.To ensure that the fibers in the final complex structure are placed exactly in the direction needed,...

The potential of carbon fiber to carry load and offer stiffness is closely linked to its orientation inside a component. Common manufacturing techniques offer a limited scope to adapt fiber orientation to the internal loads. A process called Tailored Fiber Placement (TFP) allows fibers to be placed in curved patterns according to various stress sit...