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.
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Sensing When the Molding Cycle is Over: Using In-Mold Impedance Sensors in Thermoset Molding
SmartTrac impedance sensing technology provides an important new method for thermoset molders to improve cure process productivity and quality. Similar to dielectric cure monitoring impedance technology uses the changing electrical properties of the thermoset as it cures to determine the optimum time to end the cure. This paper reviews the implementation of impedance sensing technology in SMC and phenolic and presents results from several production and lab applications.
Door Module from Fibre Reinforced Plastics - A Positive Contribution to Car Manufacturing
PowerPoint Presentation at ACCE 2004.
GM Moves Toward Composite Transmission Cross Member for Full-Size Trucks
General Motors’ next generation full-size truck frames are currently 80 pounds over their targeted weight. By replacing the current steel transmission cross-member on General Motors’ full-size trucks through the application of a composite material transmission cross-member a substantial weight reduction will be achieved. Reducing the weight of General Motors’ full-size trucks will consequently increase the fleet-wide fuel economy for the company’s truck line allowing CAFE requirements to be met more easily.
Advanced GMT Applications in the Automotive Industry
PowerPoint Presentation at ACCE 2004.
D-LFT Process: In-Line Compounding & Compression Molding of Long-Glass-Fiber-Reinforced Polymers
Long fiber-reinforced thermoplastics have excellent mechanical properties and stiffness / weight ratio which is of particular interest to the automotive industry. The new in-line compounding processes for long-fiber materials offers users more flexibility as they are able to both compound and process such materials in accordance with their own formulation and also use ready-made compounds.
UV Cure: The Microwave Popcorn of the Composites Industry
Recent developments in the area of UV cured fiberglass resins and gel coats may provide significant advantages to composite parts manufacturers. These advantages lie in the area of greater speed better efficiency and the significant reduction in styrene. Interest in this later advantage has spurred commercialization of UV cured composites where regulatory pressure has required a different approach that traditional peroxide cure mechanisms.
Natural Fibers Thinking Out of the Box
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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