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Enabling Design Innovation in Automotive Composite Applications
Today many technical and economic factors are triggering increased interest in the use of composite materials for the automotive industry. The reduced cost of composites and rising steel production costs are both significant factors. With higher oil prices consumers demand lighter more fuel-efficient cars. New material forms and innovative processes are emerging to help reduce manufacturing cycle times and consolidate part counts. Demand for car customization is enabling lower production volumes better-suited for composite parts manufacturing. Finally the use of advanced simulation tools and increased domain expertise is spreading from aerospace and car racing engineering into mainstream automotive design and production. However the real enablers to any revolutionary breakthrough in composites need to be considered more closely: Engineers must be given the ability to reconsider the rationale and the way automotive components are designed in order to fully integrate all the benefits of using composites Engineers must be given the appropriate tools to freely explore alternative new methods of using and incorporating composites into the engineering and manufacturing of production cars. In this presentation the ingredients of Renault F 1 Teams unique success in composites design as well as other significant automotive initiatives will be presented to the audience. These proofpoints will demonstrate how actual design freedom domain expertise and excellence in the mastering of composites complexity can be leveraged to develop innovative solutions that unlock the potential of composites for advances in real world practical automotive engineering.
Finite Element Modeling of Composite Tubular Crash Structures With an Explicit Code
As emissions regulations tighten worldwide automotive manufacturers must look for ways to reduce structural vehicle weight. While employing alloys and exotic metals may provide a degree of weight reduction a more significant reduction can be achieved through the use of composite materials. Importantly composites have shown an ability to improve vehicle crashworthiness through higher levels of specific energy absorption and almost ideal crush characteristics. These advantages have not been exploited in mass-produced vehicles due primarily to the high cost of component manufacture and lack of computational methods for simulation of the crash behavior of such materials. While development of rapid inexpensive production processes can increase the production volume and reduce cost manufacturers will still be required to prototype components. The provision of accurate computational models for the failure behavior of composite materials will reduce the demand on manufacturers to prototype designs and ultimately result in structures of higher performance. Herein a phenomenological Finite Element (FE) modeling methodology is presented the development of which focused on the accurate consideration of the experimentally observed failure mechanisms typical of the splaying mode of failure. LS-DYNA has been employed to validate a multi-shell model of Continuous Filament Random Mat (CFRM) glass/polyester tubes. This modeling approach utilizes a spotweld approach to modeling delamination with deformable beam elements. Typical constraint-type delamination approaches do not allow shear deformation prior to delamination and result in an inaccurate representation of laminate stiffness. Spotweld validation simulations were performed on 3-point-bend Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests with excellent correlation before application in full-tube simulations. Initiation of the splaying mode of failure was accomplished by pre-definition of a debris wedge the geometr
Measurement of Static and Dynamic Friction Energy Absorption in Carbon/Vinyl Ester Composite
Experiments have suggested that sliding friction plays an important role in the energy absorption of composite crush tubes. In an attempt to separate the sliding friction specific energy absorption SEA from the SEA attributable to matrix damage due to bending an innovative strip testing fixture was designed fabricated and tested. With this fixture strips of composite can be crushed under two fixture configurations; with and without sliding friction. The resulting load vs. deflection data is then analyzed to calculate SEA attributable to sliding friction. Strips of braided carbon/vinyl ester composite were tested statically and dynamically. The relative SEA attributable to sliding friction similar to that found when a tube is crushed with a plug type trigger was measured. It was observed that matrix damage due to bending did not change significantly when loaded dynamically compared with the quasistatic result. Sliding friction SEA however did show significant decrease when loaded dynamically vs. the quasistatic result and accounts for nearly all of the difference in SEA between dynamic and quasi-static loading.
Dynamic Energy Absorption Modes of Braided Carbon/Vinyl Ester Composite Crush Tubes
Energy absorption of fiber reinforced composite structures is of interest to the automotive industry as their specfic energy absorption SEA) i.e. the energy absorption capability per unit mass is higher than many metallic counterparts.The SEA of composite structures has been observed to decrease under dynamic crush loading when compared with quasi-static compression. The observed energy absorbing modes include tube corner splitting composite delamination matrix damage due to bending and sliding friction of the composite with a plug type crush trigger. Corner splitting was estimated to absorb less that 1% of the total energy absorbed. Energy absorption attributable to delamination was estimated to be 2.8% of the crush tube SEA. The SEA attributable to matrix damage from bending was 62.2% for quasi-static loading and 78.1% under dynamic loading. The percentage of total SEA attributable to sliding friction between the plug type trigger and composite tube was 34.8% under quasi-static loading and 18.1% under dynamic loading. The decrease in sliding friction SEA of 6.3 J/gm accounted for nearly all of the decrease in crush tube SEA of 6.6 J/gm between dynamic crush and quasi-static compression. Sliding friction was concluded to be responsible for the decrease in overall tube SEA when compression loaded at a quasi-static rate vs. a dynamic rate.
Innovative Use of Thermoplastic Film Adhesives in Automotive Airbags
Side curtain airbags or headbags are a recent development in the automotive airbag industry. They aim to reduce injuries as a result of roll over accidents. A side curtain airbag has to stay inflated for a minimum of six seconds and to reach this goal silicone layers of 90g/m² and more have to be used. This technique has several draw backs. TRW Occupant Restraint Systems one of the worlds largest airbag-suppliers developed together with adhesive company Collano a multi layered thermoplastic composite film to substitute silicone by a much thinner coating with excellent friction and air proof properties. Author will demonstrate how this development was accomplished and which properties have been achieved.
Application of Fibre Assemblies as Damping Elements in Automotive Industry
This investigation aims to characterise the damping properties of the nonwoven materials with potential applications in automotive and aerospace industry. Nonwovens are a popular choice for many applications due to their relatively low manufacturing cost and unique properties. It is known that nonwovens are efficient energy dispersers for certain applications such as acoustic damping and ballistic impact. It is anticipated that these energy absorption properties could eventually be used to provide damping for mechanical vibrations. However the behaviour of nonwovens under dynamic load and vibration has not been investigated before. Therefore we intend to highlight these aspects of the behaviour of the nonwovens through this research. In order to obtain an insight to the energy absorption properties of the nonwoven fabrics a range of tests has been performed. Forced vibration of the cantilever beam is used to explore damping over a range of resonance modes and input amplitudes. The tests are conducted on aramid glass fibre and polyester fabrics with a range of area densities and various coatings. The tests clarified the general dynamic behaviour of the fabrics tested and the possible response in more real application condition as well. The energy absorption in both thickness and plane of the fabric is tested. The effects of the area density on the results are identified. The main absorption mechanism is known to be the friction. The frictional properties are improved by using a smaller fibre denier and increasing fibre length this is a result of increasing contact surface between fibres. It is expected the increased friction result in improving damping. The results indicate different mechanism of damping for fiber glass fabrics compared to the aramid fabrics. The frequency of maximum efficiency of damping is identified for the fabrics tested. These can be used to recommend potential applications.
New Textile Composites with Thermo-Regulating Properties for Automotive Interior Applications
Energy can be saved and the thermal comfort inside the passenger compartment can be enhanced by the application of textile composites with thermo-regulating properties. The thermo-regulating properties are provided by the application of phase change material (PCM) ± a highly productive thermal storage means. In order to create the textile composites with thermo-regulating properties the PCM is contained in a polymeric film that is laminated to a textile carrier. A study has indicated that the application of the developed composites is especially beneficial in car seats headliners and instrument panels. In the paper specific solutions for the application of the textile composites in car seats headliners and instrument panels will be introduced and test results received in rigorous field tests will be discussed.
Mechanical Recycling of Injection-Molded Wood-Thermoplastic Composites
Wood-thermoplastic composites are usually processed by extrusion, and therefore an attempt has been made to study their suitability for injection molding. The experiments were made to study the behavior of the wood flour-polypropylene composite during injection molding, and to what extent the mechanical properties deteriorate after several processing cycles, i.e. mechanical recycling.
Using Vent Temperature to Sense Mold Cavity Melt Flow
A temperature sensor was placed in the vent of a single cavity mold. It sensed the closing and injected melt front that forced the gases out of the cavity. Than the temperature change from mold close melt time to mold opening. The molding cycle vent temperature profiles will be presented.
The Infinitely Variable Dynamic Shear Mixer, IDMX
Mixing is one of the most important processes in the plastics industry. Two mechanisms occur in mixing: dispersive and distributive. Different types of mixers have been developed to fulfill both mechanisms.A special mixing unit was studied. Polycarbonate, ABS and regrind were investigated. The output of the mixer was investigated as a function of the screw speeds of the satellite extruders. Qualitative measurements were carried out to characterize the efficiency of mixing at different concentration levels of the components. Conclusions were made on the effect of the parameters of mixing.
Kinematics Model of Solids Conveying of LDPE with a Grooved Barrel
The kinematics model and solids conveying angle approach are used to analyze and calculate the solids conveying flow of LDPE with a grooved barrel. The result is an excellent prediction of solids conveying flow versus pressure for a grooved barrel extruder that does not require knowledge of friction factors.
Scratch Behavior of Polymer Coatings
A recent standardized scratch test methodology was applied to investigate the performance of a set of experimental acrylic coatings. Coating ductility and coating thickness were varied to study how the affect coating cohesive strength, adhesive strength and chipping resistance. The usefulness of the new ASTM scratch test for polymer coatings is discussed.
Characterization of Amorphous and Crystalline Orientation in Polyethylene Films
Molecular orientation in amorphous and crystalline phases affects tear and dart properties of polyethylene films. This paper will describe FTIR, X-ray, shrinkage and shrink tension methods for measuring orientation. Orientation and properties of the films will be correlated to molecular structure.
Understanding Why Adhesion in Extrusion Coating Decreases with Diminishing Coating Thickness, Part II: Non-Porous Substrates
It is well known that in the extrusion coating process, adhesion to aluminum foil and other non-porous substrates decreases with decreasing coating thickness. Several hypotheses are proposed for the source of this decrease, including a reduction in time in the air gap, faster cooling in the air gap, more rapid quenching in the nip and stress imposed during drawing. Modeling and experimental results show that cooling in the nip and stress have the greatest impact.
Using Solid Freeform Fabrication (SFF) Techniques for Mold Cores and Cavities
Opportunities and limitations using SFF-techniques to design mold inserts are presented in this paper. With the aid of SFF it is possible to generate almost any cooling channel layout in mold cores. Therefore, a better targeted, faster heat removal and simultaneously better temperature homogeneity are feasible. Especially in localized Hot-Spot areas SFF techniques are able to improve the heat exchange. However, specific characteristics (pressure drop, thermal homogeneity, mechanical behavior) have to be considered.
The Long Term Behavior of Organotins in PVC Pipe
Organotin stabilizers have been used in PVC pipe for many years. These pipes are tested when made to insure that the level of organotin leaching from the pipe does not exceed a specific maximum value. This paper examines the fate of the organotins after prolonged use in PVC pipe.
Lubrication Mechanism in Poly(Vinyl Chloride) Compounds: Understanding Three Distinct Roles of Lubricants
Poly(vinyl chloride) (PVC) compounds require metal lubrication and polymer to polymer lubrication for good processing performance. This paper helps understand the lubrication mechanisms and roles. The lubricants’ roles are defined in terms of 1) metal release, 2) PVC primary particle to PVC primary particle flow unit lubrication, and 3) synergistic slip in a layer working with the first two functions of the lubricants. The optimization of these lubricant functions requires a combination of lubricants (surfactants) of various structures.
A Solution for Rupture of Polymeric Sheet in Plug-Assist Thermoforming
Rupture of polymeric sheets is one of the practical problems during plug-assist thermoforming. This defect may occur both in the stage of mechanical stretching with plug, and in vacuum or pressure thermoforming. The results shown in our work not only leads to the understanding of the cause of this problem, but also enables us to formulate calculation of parameters that affect rupture of polymeric sheets during plug-assist thermoforming for production of axisymmetric polymeric articles.
Effect of Injection Molding Process Parameters on the Morphology and Quality of Microcellular Foams
The effects of injection process parameters for microcellular foams are investigated by two stages: plasticizing to make single-phase solution, and molding to make microcellular foam. The quality of the foam is evaluated by the morphology. It is obvious that the parameters from these two stages have different effects on the quality of the foam. The quantity analyses of molding and plasticizing parameters result in some new injection processing guidelines for the quality of microcellular foams.
Effects of Gas Content and Pressure Drop Rate on Foaming
Computer simulations of polystyrene (PS) /carbon dioxide (CO2) batch foaming processes were conducted to elucidate the effects of gas content and pressure drop rate on cell-nucleating and growth phenomena. The simulation results were carefully compared with in-situ visualization data obtained experimentally. The results indicate that increases in both dissolved gas content and pressure drop rate will augment the final cell density, reduce the average cell sizes, and improve the bubble size uniformity.
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