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Conference Proceedings
Natural Fibers Thinking Out of the Box
Garry E. Balthes, Harry R. Hickey, September 2004
Most people are aware of what natural fibers are but few know of the diverse capability of this natural resource and unfortunately industry pressures over the past several years to reduce costs focused on trying to refine well established technologies using glass or wood fibers or to a certain extent injected molded polymers. It has only been through recent pressure by some of the larger OEM’s that natural fibers have been gaining broader interest for both their performance and environmental benefits as compared to older more comfortable based technologies. Cost versus performance is a delicate balancing act. Fortunately natural fibers go a long way on striking a balance between both of these most common demands. When considering performance natural fibers offer an unlimited range of lighter weight possibilities for interior and exterior applications. Most common today natural fibers are commingled into a nonwoven mat with fiberized thermo plastic polymers such as polypropylene and polyester for use in common interior applications that include door panels center consoles pillars and inserts. However advancements in the range of available natural fibers and specialty polymers along with a continuous improvement of the nonwoven process are now providing for greater heat stability to meet the elevated requirements for over head systems package trays and topper pads. Increased demands for occupant safety give further reason to consider natural fibers as few other materials provide the same impact characteristics with the base material. For exterior applications natural fiber mats used as the base material in sheet molding compounds will find their way into bumper reinforcements wheel well liners and under hood applications. The industry historically focused on direct material cost. In this simplified approach natural fibers seldom will come out to be the low cost alternative but when considering the benefits derived from one-step processing the end cost of the finis
Novel Thermoplastic Foam Structural Core Material with Enhanced Thermoformability Fatigue Endurance and Elevated Temperature Properties
Kurt Feichtinger, Wenguang Ma, Tristan Touzot, September 2004
Recent advances in thermoplastic resin chemistry have enabled the development of a thermoplastic polyester foam core material with excellent thermoformability elevated temperature and chemical resistance and superior fatigue endurance. Possessing high strength and rigidity this foam product fulfills the demanding requirements for structural core materials used in sandwich composites though it can be successfully used without facings for many applications. Presented will be the physical properties including at elevated temperatures in comparison with rigid polyurethane foams and other core materials. The results of an extensive sandwich flexural fatigue study will also be reviewed and discussed. Finally examples of complex thermoformed shapes will be shown both of the foam alone and in combination with GMT facings to form contoured structural sandwiches all at once.
Development of Sustainable Nanocomposites from Cellulose Ester for Automotive Applications
Hwan-Man Park, Manjusri Misra, Amar K. Mohanty, Lawrence T. Drzal, September 2004
Sustainable nanocomposites have been successfully fabricated from renewable cellulose acetate (CA) environmentally benign triethyl citrate (TEC) plasticizer and organically modified clay. The effects of processing conditions such as mixing methods pre-plasticizing times retention times (RT) and addition of compatibilizer maleic anhydride grafted cellulose acetate butyrate (CAB-g-MA) on the performance of these nanocomposites have been evaluated. The cellulosic plastic with CA/TEC (80/20 or 75/25 wt. %) was used as the polymer matrix for nanocomposite fabrication. The morphologies of these nanocomposites were evaluated through X-ray diffraction (XRD) Atomic force microscope (AFM) and transmission electron microscopy (TEM) studies. From all the sequential mixing methods used powder-powder mixing leads to the most transparent nanocomposites. Cellulosic plastic-based nanocomposites obtained using increased pre-plasticizing times and RT showed better-exfoliated structures. Cellulosic plastic-based nanocomposites with 5 wt.% compatibilizer contents showed better-exfoliated structure than the counterpart having 0 or 7.5 wt.% compatibilizer contents. Polygonal shape of exfoliated clay platelets was observed with 500 nm width and 800 nm length by AFM and TEM imaging. The mechanical properties of the nanocomposites have been correlated with the XRD and TEM observations.
Baypreg® F Composite Modeling
Ron Cageao, Jim Lorenzo, September 2004
Bayer MaterialScience has focused on developing new composite technologies combining a lightweight low-density core together with fiber-reinforced polyurethane skins. A Bayer MaterialScience polyurethane chemistry designated Baypreg®F is ideally suited for constructing composites that require a high stiffness to weight ratio. The components of a composite made using these chemicals can be easily manipulated to allow part producers extensive freedom in manufacturing a wide variety of part designs and configurations. This paper presents the development of a mathematical model for the prediction of composite properties. It specifically focuses on composites constructed with paper honeycomb as the core material and with glass fiber mat as the facing material. For typical composite applications load-deflection behavior is the most significant indicator of performance. Subsequently data accumulated from the testing of the core and facing materials individually is used to predict the load-deflection behavior of a composite constructed utilizing the polyurethane chemistry. The theoretical predictions are compared directly to test data obtained from composites with specific constructions. A discussion of the model’s predictive ability focusing on part design to meet customer requirements quickly and efficiently will be presented. Work targeted towards refining the model will serve as a conclusion to the discussion.
Attachment Strategies for Baypreg® F- Sandwich Composites
Ignacio G. Osio, Gregory Linder, September 2004
New automotive applications of sandwich composites require the development and characterization of reliable attachment techniques needed for the creation of functional structures. Baypreg®F is Bayer’s proprietary name for the two-component polyurethane material that bonds and holds the composite structure together which is normally made of a honeycomb-type paper core sandwiched between glass fiber mats. In this paper we present testing results to compare different attachment strategies applicable to this type of sandwich composites. As joints are a potential source of stress concentration and weight increase their performance should be as good as if not better than the underlying composite. We compare the performance of adhesive bonds embedded inserts and mechanical fasteners and discuss their advantages and disadvantages. Furthermore we discuss characterization of attachment techniques for computer simulations and outline plans for further development and testing.
Damage at Holes in Bolted Composite/Steel Joints for Heavy Vehicle Chassis Components
Lynn Klett, Barbara Frame, Vlastimil Kunc, September 2004
In May 2003 Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) began collaboration on a four year research effort focused on developing technically robust and economically attractive joining techniques to overcome the technical issues associated with joining lightweight materials in heavy vehicles. This work is being performed concurrently with an industry program led by Delphi to develop and commercialize composite chassis components which is a “focal project” that will utilize the improved joining methods. The initial joint design for a composite component to steel member will likely include mechanical fasteners requiring holes in the composite member. Several hole fabrication methods have been evaluated including drilling with tapered and Forstner bits laser cutting water jet cutting and punching. Several methods have been used to determine the damage associated with hole fabrication. One non-destructive method flash thermography has good correlation with x-ray dye penetrant results and in some cases shows finer detail and can indicate the location of damage through the thickness of the composite. A testing methodology has been developed to study the effects of bolt torque level on a pultruded fiberglass composite material. Informati on derived from this will ultimately support the characterization of bolted composite assemblies and provide insight for the design and manufacture of the composite chassis components. Loss of pre-load data can be used to predict the creep response in the through-the-thickness direction of the composite materials.
Static and Fatigue Strength Evaluations for Bolted Composite/Steel Joints for Heavy Vehicle Chassis Components
Xin Sun, Elizabeth Stephens, Darrell Herling, September 2004
This paper summarizes the Pacific Northwest National Laboratory (PNNL’s) progress-to-date on the development of joint designs for a composite structural member attached to a metal member for heavy vehicle chassis components. The joint design baseline was first established by characterizing the static and fatigue strength of a steel/steel Huck bolt joint assembly. The effects of various manufacturing factors and operational conditions on the static and fatigue strength of the hybrid joint were studied with a commercially available composite material. It was found that loading mode and washer size have significant influence on the static and fatigue strength of the hybrid joint. In addition it was found that a test frequency of 15 Hz can be used for the hybrid joints without inducing significant temperature changes during fatigue testing.
Design And Validation of a Thermoplastic Composite Liftgate
Peter H. Foss, Charles C. Mentzer, Douglas W. Franklin, September 2004
A thermoplastic composite version of a typical SUV liftgate was designed and built to investigate mass reduction over the production steel design. This paper documents the comparison of experimental stiffness of the liftgat e with predictions using several finite element models of increasing detail. One of the most time consuming aspects of modeling the stiffness of composite structures is modeling panels stiffened with ribs. Creating and meshing each individual rib represents a significant time investment. By using isogrid ribbed panels to evaluate the structural stiffness of panels stiffened in specific areas many different rib heights thicknesses spacing etc. can be modeled in a very short time. However care must be taken that the isogrid ribbed areas are feasible within geometric constraints imposed on the future detailed design. We will show that when properly applied the concept of modeling ribbed areas of panels with the isogrid simplification gives excellent accuracy.
Development of Thermoset Mold Flow Analysis for Thermoset Fuel Cell Stack Plates
Jeffrey Zemsky, Paul J. Gramman, September 2004
Highly filled thermoset compression-molded fuel cell stack plates are key elements in the design of a high-performance low-cost fuel cell stack. Much analysis research and testing have been performed to meet performance and manufacturability criteria for these plates which contain complex geometry and must meet exacting tolerances in some areas. A current deficiency in the development process is the inability to predict mold filling for the stack plates in a process with highly filled thermoset composites and compression molding. Mold-filling analysis can be used to optimize plate design mold design and the manufacturing process thereby saving time and improving quality. This paper will discuss a strategy to develop mold-filling analysis with the goal of cultivating a predictive tool for use in the manufacture of fuel cell stack plates and highly filled thermoset composites. A series of molding trials was performed and the results were used to calibrate a model resulting in a model that correlated well to the real-world case.
Affordable Lightweight Load Floors using 100% Polypropylene Materials
Derek Riley, September 2004
The marine aircraft and heavy truck transport industries have long used structural and semi-structural sandwich panels for their excellent performance/weight ratio. More recently the automotive industry has also discovered the advantages of lightweight sandwich constructions mainly for interior applications such as load floors and rear parcel shelves. However for high-volume applications there are the additional demands of low cost and for European markets in particular full recyclability. A new sandwich construction based on a 100% PP solution could be the answer. A combination of an extruded PP hollow structure covered in-line with a self-reinforced PP skin offers light weight good mechanical performance resistance to moisture and chemicals good thermoformability full recyclability using existing channels and a good cost/performance ratio.
Creative Thermoplastic Composite Materials for Use in Automotive Load Floors
Rich Simmons, John Stoll, Lloyd Hilligoss, September 2004
This paper offers a glimpse at emerging technology related to the application of composites in automotive structures. In a practical embodiment of this technology composites comprised of thermoplastic polymers and fiberglass are married with a structural core and garnished with a decorative carpet to form an automotive load floor. The exclusive polymer used throughout this particular load floor is polypropylene. Thus the composite structure is comprised entirely of polypropylene and fiberglass. Among the major advantages of this design are the following characteristics: structural integrity low weight excellent thermal stability acoustic abatement incorporation of recycled raw materials and the opportunity for end-of-life component recycling. Regarding processing of this load floor additional key advantages exist such as: low cycle time good formability one-step part consolidation high automation and the low environmental impact associated with thermoplastic polymers. Conceptually products of this type promise to have a lasting impact on the environment through all phases of product life cycle. This is achieved at first by utilizing recycled raw materials going into the product. Next offal from processing is recycled back into the materials stream. In addition the system creates a product of a known common composition of materials which possesses a higher potential for recycling as a whole after the useful life of the vehicle.
Advanced Composites on the Ford GT
Eric Kleven, Dan Houston, J.T. Lyons, September 2004
The presentation will review the engineering considerations that led the Ford GT team to the development of the industry-first one-piece carbon fiber inner panel for the rear deck enginer cover and the associated manufacturing process. While most of the structural components of the 2004 Ford GT are aluminum the size of complexity of the rear deck drove the team to use carbon fiber for the inner structure. Instead of using multiple stamped aluminum pieces to make the inner structure the team decided to use carbon fiber composite technology to reduce weight control dimencional accuracy and for the total program cost benefit. The paper will also discuss the manufacturing of the component by Sparta Composties Inc (Sand Diego CA). The deck inner is made by hand lay-up of unidirectional carbon fiber/epoxy prepreg on an Invar mold for autoclave cure. In order to achieve the full-production rate of this complex panel a number of techniques are employed including a laser placement system which simplifies lay-up operations.
The Case for Replacing Steel with Glass-Mat Thermoplastic Composites in Spare-Wheel Well Applications
Marcia Kurcz, Burak Baser, Harri Dittmar, Joachim Sengbusch, Hans Pfister, September 2004
This paper will discuss the use of glass-mat-ther moplastic (GMT) composite to replace steel in spare-wheel wells (SWW) by European automakers and tier suppliers. Although this application has been successfully translated across multiple OEMs and platforms in this geography for 10 years it is still little known and less understood in the Americas and Asia/Pacific despite its numerous advantages. In an attempt to help automakers and tier suppliers in other parts of the world understand the benefits of this technology the paper will discuss OEM performance criteria design requirements tooling and manufacturing of the part as well as requirements for finished assembly in to the vehicle vs. traditional steel systems.
Bonding CFRP-Metal Structures in Vehicles
Tino Fuhrmann, O. Hahn, September 2004
As weight reduction is required for ecological aspects and in certain areas of the vehicle for dynamic handling requirements and besides this metallic materials cannot be extensively substituted within the short-term structurally bonding metallic materials with CFRP is necessary. Cathodic dip painting (CDP) which precedes the bonding process is able to offer good protection in order to combat sub-surface corrosion (bondline corrosion) which is also familiar from bonded metal joints. If the CFRP structural part has to be painted together with the entire body-in-white the CFRP component and therefore the joining process may be integrated into the production sequence directly downstream of CDP. If joint painting is not necessary the joining process may be carried out at the beginning of assembly directly following paint drying. High thermomechanical stress in the production process can therefore be avoided and the problem is reduced to the vehicle's operating temperature range. The paper shows the characteristic properties of different adhesive systems e.g. two-component epoxy polyurethane or methacrylate in bonded CFRP-metal joints based on quasi-static test results. Especially the requirements on withstanding thermomechanical stresses in production and vehicle's operating temperature range are shown and evaluated by tests at different temperatures. The results shown in this article are developed in a cooperation project of Volkswagen AG Wolfsburg LWF Transfer GmbH & Co. KG and LWF Paderborn University Germany.
pCBT: A New Material for High Performance Composites in Automotive Applications
Michael Shoemaker, Dave Bank, Peter Cate, September 2004
Cyclic oligomers of butylene terephthalate (CBT®) represent a new chemical route to semi-crystalline thermoplastic polybutylene terephthalate (PBT). The oligomers of interest melt completely at about 150°C to produce a low-viscosity fluid that is ideal for wetting and dispersing fibrous fillers and reinforcements thereby enabling the development of composites that were previously not possible when working with high-viscosity commercial PBT. Introduction of catalyst to undiluted molten cyclic oligomer leads to rapid ring opening polymerization and the formation of high-molecular-weight thermoplastic PBT without the generation of volatile organic compounds. The polymer resulting from this polymerization will be hereafter referred to as pCBT. Treatment of cyclic oligomers in this fashion results in pCBT thermoplastic resin with a high melting point (230°C) and physical performance similar to that of other commercially available PBT resins. The low viscosity of these oligomers enables the selection of processing technologies that are typically reserved for thermosetting systems and that work in conjunction with easy flowing monomers or pre-polymers. The combination of excellent mechanical performance and the ability to utilize processing techniques typically reserved for thermosets enables broad uses for these oligomers in a range of applications including interior exterior and structural automotive components. Additionally the thermoplastic nature of pCBT holds promise to provide a low-capital route to a new family of pCBT-based recyclable materials made using a range of plastic processing technologies.
Evaluation of an Aromatic Amine Antioxidant in Glass-filled Poly(propylene)
Michael E. Gelbin, September 2004
Glass-mat reinforced thermoplastic (GMT) composites have increasingly begun to replace traditional sheet molding compounds in automotive applications owing to their reduced weight. Both processing and end use put special demands on the stabilizer package incorporated in the poly(propylene) resin phase of the GMT composite. A novel ternary antioxidant blend based upon an aromatic amine type stabilizer for superior processing stabilization in GMT will be presented. Processing stabilizer performance data as measured by the critical weight loss test at 230 °C will be discussed. Comparison of the arylamine based blend which is phosphite-free with a traditional phosphite-containing package of otherwise similar composition confirmed the superior performance of the former.
High Performance Natural Fibre Reinforced Sheet Molding Compound for Automotive Applications
Merry Lo, Suhara Panthapulakkal, Mohini Sain, September 2004
This research work aims to replace glass fibres in sheet molding compounds (SMC) by renewable natural fibres. These eco-efficient and cost effective SMC with natural fibres are gaining much attention in the automotive industry because of their specific properties. The specific objective of the work was to develop a high performance natural fibre hybrid SMC to meet the specifications required for automotive parts such as front fenders body panels etc. Hemp fibres with and without a combination of a small amount of glass fibres were used to reinforce vinyl ester resin for making SMC. Different combinations of layers of hemp and glass fibres were made to prepare SMC. Mechanical properties such as tensile and flexural properties and impact strength of the SMC prepared were found to be highly promising. The current OEM specifications for automotive parts for example rare lift gate and front fenders recommend the composite should have tensile strength of 62 MPa and tensile modulus of 2 GPa (Source of Automotive Engineers Car Technology yearbook 2000” USA 2000 Body panels Properties). SMC prepared by the combination of 45% of hemp fibres and 5% of glass fibres showed tensile strength and modulus were more or less same or better than that of the requirements for car body parts such as rare lift gate and front fenders (Tensile strength greater than 62 MPa and tensile modulus of 2 GPa).Use of this SMC with natural fibre is an economically viable alternative to SMC with glass fibres and at the same time it helps reducing the green house gas emission as there is lesser amount of synthetic resins and plastics.
Development of New Green SMC Resins and Nanocomposites from Plant Oils
Jue Lu, Richard P. Wool, September 2004
Sheet molding compound (SMC) is widely used in automotive parts appliances furniture and construction. These materials heavily depend on the petroleum supply which is depleting fast. The use of plant oils as an alternative source for SMC resins presents economic and environmental advantages over petroleum. Two synthetic methods have been used to develop new resins from triglycerides. The double bonds presented on the fatty acid chains were first converted to epoxy or hydroxyl functionality; the hydroxyl groups were maleinized while the epoxies were acrylated and then further maleinized. When these functionalized oils were combined with 33.3 wt% styrene the polymers showed mechanical properties comparable to those of commercial unsaturated polyesters. In addition these new resins exhibit adequate thermo-reversible thickening behavior with MgO. These triglyceride-based resins have good compatibility with natural fibers such as hemp and flax to form low-cost green composites. New bio-based nanocomposites were also developed using these new resins and organo-treated clays and the nanocomposites showed considerable increase in modulus and toughness. These new green materials show the promise to be used in the automotive industry.
Process for Manufacturing a High Performance Natural Fiber Composite by Sheet Molding
T. Behzad, M. Sain, September 2004
In the past few years natural fibers are finding an increased interest in polymer matrices. The natural fibers serve as reinforcement by enhancing the strength and stiffness to the resulting composite structure. In this study a novel processing technique has been developed for water based thermoset polymers to prepare resin-impregnated mats which can be used for sheet molding process to manufacture complex automotive semi-structural and structural parts. In order to optimize the curing conditions the mechanical properties of composites at different curing temperature and the crosslink density of the composites cured at different times were evaluated. The optimum curing cycle was obtained at 180 ºC for 10 min. Composites with one and two layers of impregnated mat with 40 % resin and 60 % fiber were manufactured and their performance were evaluated. The mechanical properties of the cured pure resin and hemp fiber acrylic based composites with two different fiber lengths were measured and the effect of fiber content and fiber length were investigated. The flexural strength was found to be around 94 MPa and the flexural modulus was 14 GPa for the composite.
Electron Beam Curing Demonstration with Automobile Structures
C.C. Eberle, C.J. Janke, C.S. Wang, September 2004
Continuous carbon fiber/epoxy automobile hoods were electron beam cured to demonstrate the capability to achieve curing throughput rates needed on automotive production lines. The project team demonstrated curing speed of 180 hoods/day. This demonstration extrapolates to 1600 hoods/day curing throughput using a more powerful electron accelerator and much higher throughputs may be achievable with innovative design and materials development. Single-pass curing was shown to be feasible. The curing costs are potentially attractive especially at high production volumes Test laminate properties considerably exceeded those of the finished hoods. Hood thermo- mechanical properties and surface finish need improvement. This is not surprising since this was the team’s first attempt to manufacture electron beam cured automobile structures. Several technical barriers were identified that need further attention.


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