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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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.
pCBT: A New Material for High Performance Composites in Automotive Applications
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)
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
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
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
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
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.
Equal-Channel Angular Extrusion of Thermoplastic Matrix Composites for Sheet Forming and Recycling
Equal channel angular extrusion creates novel properties in metal and polymer materials. Recently the authors investigated the effects of this process on commercial short fiber composites. Experiments show that ECAE provides a means for controlling fiber length and orientation in the extrudate. The process might transform continuous fiber thermoplastic matrix composite sheets into high volume fraction discontinuous fiber sheet for thermoforming. In addition the process might provide a method of recycling reground components into high-value sheets with a known fiber orientation.
The Effect of Surface Energy of Boron Nitride on Polymer Processability
Fluoropolymers have long been used as processing aids for surface melt fracture treatment of polyolefin extrudates. Recent developments have shown that a small amount of Boron Nitride powder successfully eliminates surface melt fracture and also delays the onset of gross melt fracture. Study of surface energy helps in understanding the different mechanisms of these two processing aids in eliminating extrudate melt fracture.
Fundamentals of Melt Fracture Elimination Using Fluoropolymer Process Aids
Fluoropolymer process aids are widely used in polyolefin blown films to eliminate melt fracture. These process aids function by depositing a thin fluoropolymer layer on internal die surfaces, and promoting slip at the fluoropolymer – polyethylene interface. The present work describes how the morphology of fluoropolymer – polyethylene blends can be controlled to increase fluoropolymer deposition rate by using a new, rheology-modified fluoropolymer in combination with an interfacial agent.
A Survey of Manifold Designs for Flat Die Extrusion
Feedblock Coextrusion is considered to have been commercialized with the Dow Chemical patents issued in 1971. As Cloeren and Nissel introduced their own Coextrusion technology, a common thread throughout all technologies was design of Coextrusion dies. For decades extrusion die manifold designs remained unchanged. The ‘90s ushered in new commercial manifold designs aimed at solving age old problems with flow uniformity, die deflection, and coextrusion performance. This paper will examine the progression of die manifold designs, their impact on extruded products, and their implications on future coextruded structures.
Blown Film Characterisation
Effects of process changes on polyethylene blown films were studied using profile analysis techniques. The relationship between process parameters, barrel temperature, haul off rate and die gap, and film properties, thickness, blow up ratio (BUR), freeze line height, consistency of bubble profile were studied. An optical analysis system was developed which allowed film characteristics to be monitored during processing.
The Effect of Orientation on the Mechanical Performance and Thermal Properties of Extrusion Cast Metallocene Polyethylenes
Cast films were prepared using a Killion single screw extruder, from a range of metallocene PEs of varied comonomer types (hexene, octene), using different haul off speeds (8-4m/min) and die gaps (700-250?m). It was found that samples with greater orientation in one direction had increased tensile strength and shrinkage in that direction. DSC analysis showed crystallinity to decrease with decreasing haul off speed.
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