The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
GE Plastics pioneered the use of thermoplastics for vertical body panel applications (such as fenders door skins and lift-gate skins) and now a thermoplastic composite material for horizontal automotive body panel applications (such as hoods roofs and trunk lids) is underdevelopment. One of the challenges to be met by a new material for hood applications is to meet the new requirements for pedestrian protection that have been introduced in Europe and Japan. As one of the key technology developments carried out for the Hyundai HED -4 QarmaQ advanced technology demonstration vehicle developed by Hyundai and GE Plastics a new hood design was created for manufacture with the HPPC sandwich. Semi-production compression-molding tooling was built and parts were produced to enable a series of head-impact tests to be completed. The test results indicated that the energy absorption characteristics of HPPC allow such a hood to meet the pedestrian safety requirements without the need for extra intrusion into the engine bay.
The introduction of long-fibre reinforcements into the matrices of polymeric materials has lead to the development and introduction of many engineered solutions for applications which had once solely been the province of metal designs. The combination of long glass fibre with a highly economical and processable polymer such as polypropylene has significant advantages for both the designer in terms of weight reduction design flexibility and cost savings as well as to the moulder in terms of efficiency and productivity. The utility of this polymeric solution is further enhanced when it can be combined with unique bonding materials to allow it to be bonded with metal for structural enhancement. This paper will review the development of a long glass fibre polypropylene polymer in concert with the development of a unique adhesive solution to form a polymer- metal hybrid solution. This utility and effectiveness of this solution will be demonstrated in the structural modular application of an automotive front end carrier.
Unsaturated polyester resins based on renewable resource raw materials (soy and corn) have been commercially available since the late 1990s. These resins have successfully been formulated into sheet molding compound and are compression molded into parts used by the John Deere Corporation to manufacture farm machinery. This paper will discuss the economics and environmental effects of using renewable resource based composites describe the current applications where the technology is being used and consider the future of bio based technology in the composites industry.
Plaques fabricated from sheet molding compound (SMC) with soy-based resins in both glass fiber-reinforced and carbon fiber-reinforced versions are compared with the equivalent SMC with petroleum-based resins. Since soy-based resins are less sensitive to the price of petroleum than petroleum-based resins these materials represent potential cost savings to the automotive industry if the price of petroleum continues to increase as well as providing opportunities to decrease overall carbon dioxide emissions. Soy beans are also a renewable resource. Material thermal properties including dynamic mechanical analysis (DMA) and coefficient of linear thermal expansion (CLTE) are evaluated as are mechanical properties including tensile and compressive characterizations. The effect of humidity aging was evaluated by moisture absorption as well as residual tensile and compressive properties. For as-received properties the glass-reinforced version of the soy-based material is found to be similar in performance to the petroleum-based material. However the carbon-reinforced soy resin material has lower mechanical properties than the petroleum-based SMC probably due to a lack of fiber-matrix adhesion. In humidity aging the petroleum based materials absorbed less moisture than the soy-based although the relative property loss caused by humidity aging was similar for the petroleum-based and the soy-based materials.
The 2007 redesigned Nissan Sentra includes a unique trunk divider panel system that utilizes several different composite materials. The multi-piece (hybrid) main panel consists of a compression molded SMC ‘inner’ panel an in-mold carpeted flax fiber-filled polypropylene ‘outer’ panel integral glass-filled grocery hooks and two-way latching mechanism. The divider panel is mounted to the vehicle via a compression molded SMC ‘upper’ panel that mounts to the vehicle’s sheet metal package shelf as well as two glass-filled polypropylene hinges that mount to the vehicle’s trunk floor. To add versatility the panel can be used in a closed position to form two trunk compartments folded flat to the floor to transport wet or muddy items or removed entirely from the vehicle for clean-up or outside use. This system meets all required cost mass performance / functionality and quality targets. This presentation will focus on the design development materials testing and manufacturing methods applied to bring this ‘hybrid’ composite system to market.
Automotive OEMs cite the difficulty in modeling composites as a significant barrier to their wider use. Unlike metals whose properties are isotropic composites have behavior that may be more difficult to model and to predict. Accurate materials characterization is increasingly important in allowing engineers to create the most cost-effective and reliable designs. In addition as carmakers make greater use of computer-aided tools detailed characterization becomes a basic requirement to consider a material for a particular application. This paper surveys some of the tools available for optimizing high volume automotive designs in thermoset composites namely sheet molding compound (SMC) and describes the range of resources from qualitative design guides to quantitative prediction models.
Based on the information generated at GM R&D Center six SMC formulations were developed and produced by SMC suppliers and subsequently molded into automotive body panels for powder primer application readiness tests. The panels were evaluated in the lab for shrinkage moisture absorption adhesion to the conductive coating and powder application. Based on the results all six formulations were approved for plant trials. The trials took place in Shreveport and Lordstown assembly plants. It was noted that the use of infrared heating to bake the powder is detrimental to SMC as it causes rapid heating of SMC substrate resulting in a high flux of moisture in a short period of time. It was also learned that the experimental conductive coating improves the powder prime capability of SMC and allows powder priming after an extended exposure to the plant environment.
The incomplete reaction of polyester resins in fiber reinforced composites results in residual styrene monomer that slowly evolves from the polymer matrix over many years. In cars and trucks where extensive use of such composites are open to the interior of the passenger compartment the odor of styrene can become strong enough to be objectionable to the vehicle occupants. A design goal for the development of coupe sports car which makes extensive use of polyester SMC and liquid molded composites was to assure that the styrene concentration in the passenger compartment is not offensive. Simple test methods were devised to assess styrene evolution at the material component and vehicle levels. Through the systematic study of resin paste formulations process modifications coatings and part design features this design goal was met before the launch of the vehicle.
This paper seeks to quantify the influence of fiber length on the mechanical properties of discontinuous carbon fiber/ epoxy laminates produced by compression molding. New interest is being generated toward low-cost composite material forms for aerospace applications. The high-volume carbon fiber content combined with aerospace-qualified epoxy resins opens up opportunities for more aircraft parts to be made of non-metallic materials. The Boeing 787 Dreamliner uses this material form for the manufacturing of the structural window frames. This material-process combination is ideal for large volume production of three-dimensional parts allowing for the molding of complex contours thickness variations and stiffening ribs. Interesting relationships between fiber length and tensile compressive and flexural moduli and strengths are observed.
The desire for weatherable sheet molding compound for use in a wide range of applications is growing due to the potential of eliminating paint or coatings on the molded article. The elimination of paint or protective coatings can result in significant cost savings and an improved environmental profile for the article. These savings can be realized if existing coating facilities are at capacity or if a green field investment is being considered. Weatherable sheet molding compound (SMC) technology has been previously available but has been designed for specific applications. Transfer of this technology into other application areas has resulted in some performance issues. This paper discusses new developments in weatherable sheet molding compound technology that allow its use in a wider range of application areas.
This paper presents an experimental-modeling approach to predict the elastic properties of long-fiber injection-molded thermoplastics (LFTs). The approach accounts for fiber length and orientation distributions in LFTs. LFT samples were injection-molded for the study and fiber length and orientation distributions were measured at different locations for use in the computation of the composite properties. The current fiber orientation model was assessed to determine its capability to predict fiber orientation in LFTs. Predicted fiber orientations for the studied LFT samples were also used in the calculation of the elastic properties of these samples and the predicted overall moduli were then compared with the experimental results. The elastic property prediction was based on the Eshelby-Mori-Tanaka method combined with the orientation averaging technique. The predictions agree reasonably well with the experimental LFT data.
Procedures for fiber length distribution (FLD) measurement of long fiber reinforced injection molded thermoplastics were refined for glass and carbon fibers. Techniques for sample selection fiber separation digitization and length measurement for both fiber types are described in detail. Quantitative FLD results are provided for glass and carbon reinforced polypropylene samples molded with a nominal original fiber length of 12.7 mm (1/2 in.) using equipment optimized for molding short fiber reinforced thermoplastics.
As a result of recent increases in fuel prices and the growing number of accident fatalities the two major concerns of the automotive industry and their customers are now occupant safety and fuel economy [1 2]. Increasing the amount of energy and optimizing the manner in which energy is absorbed within vehicle crush zones can improve occupant survivability in the event of a crash while fuel economy is improved through a reduction in weight. Axial crush tests were conducted on tubular specimens of Carbon/Epoxy (Toray T700/G83C) and Glass/Polypropylene (Twintex). This paper presents results from the tests conducted at quasi-static rates at Deakin University Victoria Australia and intermediate rate tests performed at the Oak Ridge National Laboratory Tennessee USA. The quasi-static tests were conducted at 10mm/min (1.67x10-4m/s) using 5 different forms of initiation. Tests at intermediate rates were performed at speeds of 0.25m/s 0.5m/s 0.75m/s 1m/s 2m/s and 4m/s. Quasi-static tests of tubular specimens showed high specific energy absorption (SEA) values with 86 kJ/kg for Carbon/Epoxy specimens. The SEA of the Glass/Polypropylene specimens was measured to be 29 kJ/kg. Results from the intermediate test rates showed that SEA values did not fall below 55kJ/kg for carbon specimens or 35kJ/kg for the Glass/Polypropylene specimens. When compared with typical steel and aluminium SEA values of 15kJ/kg and 30kJ/kg respectively the benefits of using composite materials in crash structures is apparent.
One of the key factors preventing the widespread adoption of composites in primary crash structures is the absence of specialized test methods for the characterization of specific energy absorption (SEA). Aside from thin-walled tubular specimens a limited number of attempts have been made at developing test specimens that are easier to manufacture. The possibility to employ a self-stabilizing corrugated plate specimen has been previously presented. In this study results from three corrugated plate geometries are compared with those of a flat plate specimen. The latter is tested using ad hoc developed support fixture which is based on an initial concept proposed by NASA/ Army. Preliminary results show that the flat specimen SEA results do not agree with those of the corrugated ones thus emphasizing the complex nature of SEA.
This work is based on coating a polymeric catalyst onto a metallic substrate by using of a surface coating technology. We have used adhesion promoters (Silane compounds) under sol-gel process in order to achieve maximum stability of coating and suitable strength properties. Structural packings produced by this method would have unique physical properties and may be used in catalytic distillation.
One emerging market for thermally and electrically conductive resins is for bipolar plates for use in fuel cells. Bipolar plates require high thermal and electrical conductivity. In this study, carbon black and synthetic graphite were added to a liquid crystal polymer and the resulting composites were tested for thermal and electrical conductivity. Single filler composites containing 2.5 to 15 wt% carbon black and 10 to 75 wt% synthetic graphite were tested.
Most consumers believe the price paid for a product is directly related to its inherent level of quality. With decorated plastics, how robust the product finish is before it becomes damaged or worn out" is an essential element of this perceived quality. This paper presents an introduction to the mechanisms of surface wear and scratch damage and the importance of conducting controlled laboratory tests. An overview of several commercially available instruments is offered including suggestions on how to recreate and measure "real-world" damage."
Thermoplastic polyurethane-carbon nanofiber, TPU-CNF, composites were prepared in situ in a chaotic mixer. Two types of CNF with different levels of surface oxidation were mixed with a shape memory TPU. Electrical conductivity, thermal behavior, and mechanical properties were investigated. Electrical and thermal-induced shape recovery behaviors were evaluated. TPU with treated CNF showed better dispersion, crystallinity, tensile properties, and better shape memory properties such as higher shape recovery force than their counterparts with untreated CNF.
Rotomolding parts with aluminum pigments has been a challenge, as this process provides limited aesthetic effects. Rotomolding compounds made by fine micro-pelletization provided a good method of aluminum pigment incorporation. Our research was to determine the benefits and limitations of this manufacturing method.
Immiscible polymer blends were prepared by melt extrusion using a single screw extruder in the systems PS/HDPE and PS/PP to assess the effect of composition and morphology on tensile Young's modulus and impact resistance. Results from the work show that tensile modulus nearly follows rule of mixture behavior for both systems, although better performance is shown by the PS/PP blends. With regard to impact resistance, the PS/HDPE system showed poor, incompatible performance, whereas excellent impact resistance was noted in the PS/PP blends.
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