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The effects of specific functionalization of montmorillonite clay on the mechanical properties of melt-processed PP/clay nanocomposites have been investigated with three different clays. Organically modified montmorillonite was subjected to appropriate silane treatment in order to functionalize the edges. Each of the organoclays was compounded with a maleated polypropylene (PP-g-MA) and a PP in the proportion 5:10:85 by wt. The clay silated in this work was confirmed by XRD to be edge functionalized. This clay led to the composite with the greatest level of exfoliation as determined by both XRD and dynamic viscosity measurements. The same composite also had the highest tensile modulus. However the flexural modulus was found to be insensitive to additional treatment of the clay. Hence the increase in tensile properties reflects the greater extent of dispersion as well as a higher degree of orientation achieved during molding.
Printout on the surface of an FRP laminate has one primary source: resin shrinkage. The very property that makes polyester resin with glass reinforcement so durable is its own enemy when surface appearance is an issue. During the curing stage of a laminate resin shrinks and glass goes not shrink. A surfacing veil added to a lamination schedule will dramatically reduce the resin shrinkage at the surface giving it a smooth and consistent resin-rich surface. A consistent resin-rich surface in the composites industry includes a corrosion barrier UV barrier a smooth finish and lower porosity. Surfacing veil added to a process can also increase efficiency including quicker resin flow in closed-mold situations earlier demold time protecting pultrusion dies strengthening the gel coat and bonding the gel coat to the reinforcement.
In the automotive industry’s incessant drive towards higher performance lightweight materials there has been much interest in the area of carbon fibres (CF) as a potential filler solution for thermoset composite materials. RRIM (Reinforced Reaction Injection Moulded) composite materials have been successfully used in automotive exterior applications such as fascia fenders claddings and truck sides for over 25 years now and have developed a reputation for offering durability functional performance design freedom and paintability to the OEM. These RIM composites have traditionally incorporated glass wollastonite or mica as high performance fillers for these applications which have a relatively high specific gravity of 2.5-2.9. The benefits that carbon fibre’s high strength-to-weight ratio and lower density could bring to the RIM polymeric network was the primary focus of this study. This paper will explore the use of carbon fibres in RIM polyurethane/polyurea composites as an opportunity to reduce weight and will explore the characteristics of the resultant composite. The paper will provide an evaluation of the performance of the carbon fibres from a perspective of processability mouldability physical properties paintability and functional part manufacture in the area of automotive exterior body panels such as fenders or quarterpanels. The study will touch upon the benefits that the developed carbon fibre composites can bring to the industry - such as light weight a relatively high stiffness-to-weight ratio a good balance of physical properties and increased electrical conductivity for improvements in paint transfer efficiency and aesthetics. The study will also discuss some of the considerations that working with carbon fibres will likely entail such as higher raw materials cost and processability limitations.
Free radical cured thermosetting vinyl ester resins have superior toughness and chemical resistance in comparison to unsaturated polyester. The use of vinyl ester composites reinforced with carbon fibers requires an improvement in the fiber-matrix adhesion levels. Previous data has shown that the application of a lightly cross-linked amine-cured epoxy sizing to the carbon fiber surface creates a beneficial interphase between the carbon fiber and vinyl ester resin matrix resulting in a substantial increase in fiber-matrix adhesion and the sizing has a optimum thickness . However the exact mechanism by which this coating improved adhesion is not known. Vinyl ester resin can undergo as much as 10% volume shrinkage with cure while typical epoxy systems undergo only 3-4% shrinkage during cure [4-6] . The cure volume shrinkage could have induced significant stresses in the fiber/matrix interphase. This could be the one of the most important factors that lowers the adhesion between carbon fiber and vinyl ester resin. In this study the influence of the matrix cure volume shrinkage on the adhesion between carbon fiber and vinyl ester resin was investigated. Adhesion was evaluated as interfacial shear strength (IFSS) measured with a micro-indentation. Finite element analyses were used to simulate stress at the interphase and matrix as well after matrix shrink. It was found that cure volume shrinkage of vinyl ester could introduce thermal residual interfacial tensile stress which would decrease the adhesion between fiber and matrix the greater the shrinkage the more significant the effect. The cure volume shrinkage was dependent on the molecular weight of the vinyl ester monomer and content of styrene content and also is related to the cure process and catalysts for polymerization. It was also found that a specially formulated epoxy-sizing which swells in a vinyl ester matrix could counteract the cure volume shrinkage of the matrix. The results from finite element analyse
Many research efforts have been focusing on exfoliated clay systems the same nanoreinforcement concept can be applied to another layered material graphite. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. If the appropriate surface treatment can be found for graphite its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are required. In this research a special thermal treatment was applied to the graphite flakes to produce exfoliated graphite reinforcements. Intercalated natural crystalline graphite compounds [GICs] were formed followed by exfoliation and milling to produce sub-micron graphite flakes. SEM and TEM images showed that the average size of graphite became 0.86 um with a thickness of around 5 nm. With the proper surface treatment the graphite nanoplatelets in polymeric matrices showed better flexural strength than composites with other carbon materials. Impedance measurements have shown that the exfoliated graphite plates percolate at below 3 vol% and the composites showed resistivity close to 101ohm*cm. The cost of this new nano-size graphite material was estimated to be around $5/lb or less. Since exfoliated graphite has superior mechanical electrical thermal properties and cost effectiveness this material has been shown to be a superior potential reinforcement for polymer nanocomposites for many applications including fuel cells batteries and composites for electrical shielding.
The 2002 Aston Martin V12 Vanquish is one of the most technically advanced cars on the road. From its extruded aluminum space-frame to its carbon fiver transmission tunnel and energy absorbing crash structures the entire vehicle is adhesively bonded together. Several adhesives are used throughout the structure to optimize performance and processing. A toughened single component epoxy adhesive is used to bond the aluminum extrusions whereas a low modulus two-component polyurethane adhesive is used to bond the aluminum extrusions whereas a low modulus two-component polyurethane adhesive is use to attach the glass fiver composite body panels. The structural composite parts such as the front crash structure and tunnel are bonded using a medium level modulus two-component polyurethane adhesive. This paper will outline the role of adhesives within the Aston Martin V12 Vanquish in particular the bonding of the twenty plus composite parts. Details of the adhesive selection corrosion durability and manufacturing issues will be presented for the front crash structure assembly.
With continued increases in energy costs the trend towards weight reduction and fuel economy in the automotive industry will further grow in importance in the coming years. However increased safety and performance are demands on which the consumer is also not willing to compromise. This paper presents a viable technology complimentary to metals for structural applications where stiffness impact resistance and functional integration are combined to form a cost effective lightweight solution. The paper examines the use of metal-plastic composite structures as a means to reduce weight while maintaining or improving performance. The metal is used where the high stiffness and strength can be exploited while the plastic composite gives a balance of stiffness and impact resistance and enables functional integration through the formation of complex shapes in the moulding process. The combination allows the optimisation of the performance and function per unit weight of the application by balancing the contribution of the metal and the plastic composite. Polypropylene (PP)-based composites have high potential for usage in many structural applications in cars due to the cost effectiveness combined with a good balance of properties. The availability of the matrix material and the extensive manufacturing capabilities globally for PP composites make this an obvious choice for a broad range of OEMs and applications. When the merits of this approach are accepted the question remaining is how to combine these two dissimilar materials. This paper shows the benefits of the use of adhesives which greatly reduce stress concentrations and spread the load compared to mechanical fastening allowing a more efficient use of materials. The choice of adhesive is discussed in combination with the plastic and metal used. When plastics with low energy surfaces are used such as polypropylene several process steps are required to achieve an effecti
In this paper the effect of stacking sequence and laminate thickness on mechanical behavior of matrix hybrid composite with mechanical joint was investigated to improve the performance of composite structures for automotives. Four types of stacking sequences of matrix hybrid and two kinds of laminate thickness were prepared. The failure maximum load depended on the characteristic of matrix resin and laminate thickness. The optimum stacking sequence especially in case of thick laminate was expected by placing conventional resin that is rigid resin into outer domain and flexible resin into inner domain.
Class 8 trucks offer substantial opportunities for weight reduction with cost incentives resulting from increased payload and improved fuel efficiency. The chassis suspension drive train and wheels contribute to approximately 40% of the truck weight and have components that are excellent candidates in terms of material performance requirements for replacement with low-density structural composite materials. However actual or perceived deficiences in joint reliability have up to now limited use of polymer composites in this application. Researchers at Oak Ridge National Library (ORNL) and Pacific Northwest National Laboratory (PNNL) have begun a project to overcome the major technical issues associated with joining thick fiver-reinforced composite sections. The initial objective is to develop both economical and robust attachment techniques for composite members joined to steel members. The research will be coordinated with an industry team led by Delphi Corporation that is developing and commercializing composite chassis members through funding from the Department of Energy's (DOE's) High Strength Weight Reduction Materials Program under the Office of FreedomCAR and Vehicle Technologies.
Fiber reinforced polymers (FRPs) are promising materials for reducing vehicle mass thereby improving energy efficiency and US energy security. Presently the cost of using FRPs especially with carbon fiber reinforcement is quite high in comparison to conventional materials and the lack of market incentives prevents their widespread use in passenger automotive structures. Furthermore the material demand from even a small passenger automotive carbon fiber reinforcement application would overwhelm the carbon fiber reinforcement application would overwhelm the carbon fiver supply chain. The Class 8 truck market offers modest financial incentives for vehicle mass reduction in some sectors and vehicle build rates are low enough that the composites industry can satisfy demand without making step changes in capacity. This suggests that a rational strategy for realizing the energy efficiency benefits of low mass composite materials in the transportation market is to develop and initially demonstrate new technology in the commercial vehicle market with migration into the passenger automotive market as the technology matures. The US Department of Energy's (DOE's) FreedomCAR and Vehicle Technologies Office is therefore funding a significant research and development effort focused on heavy truck applications.
A novel approach to optimize mold cooling using a seamless combination of simulation and optimization tools under a unified framework is presented. Heat transfer in the mold is modeled using a transient heat conduction equation with appropriate source/sink terms. Crystallization kinetics and the latent heat contribution of the polymer are also considered. Cooling passages are modeled exactly in three dimensions and also using one-dimensional cooling circuits. The latter method is used to accurately specify the heat transfer boundary conditions in the passage by separately computing the coolant flow. The keys to this modeling approach are the data structure that represents the problem domain and the interface between the solver and optimization tool. The simulation is designed specifically with optimization in mind. A sample analysis and results highlighting the methodology is presented in this work.
A lot of automobile plastic parts are made of fiber-reinforced engineering plastic for its superios mechanical properties and high heat distortion temperature. The fiber orientation and anisotropy shrinkage in injection molding are complex 3D phenomena. They are difficult to identify and stufy by the traditional 2.5 D model. The thermal and mechanics properties of the composite closely relate with the fiber orientation pattern. Thermal shrinkage is larger in transverse direction and lower in fiber orientation direction. This 3D technique is proved to be a powerful tool for the study of 3D fiber orientation and anisotropy shrinkage phenomena and a cost-effective approach for related part/mold designers.
Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process electron beam freeform fabrication (EBF3) as a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Thus far this technique has been demonstrated on aluminum and titanium alloys of interest for aerospace structural applications; nickel and ferrous based alloys are also planned. Deposits resulting from 2219 aluminum demonstrations have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm3/hr (150 in3/hr) or finer detail atlower deposition rates depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.
Rapid tooling processes have traditionally been limited in application to relatively small components. The Zoned Tooling (Z-Tool) process differs from other technologies in that it utilizes forged plate stock as its raw material and can be used to manufacture even the largest of automotive molds. Utilizing knowledge based programming features within a CAD environment a tool is sectioned into a number of segments (zones) that are then rough cut with a waterjet or milling machine and electron beam welded into the final form. Traditional roughing and gun- drilling are eliminated and finish machining and subsequent processes proceed in the normal manner. The challenges and advantages of the process are discussed along with a demonstration of a typical application.
Thermal Analysis is the generic name for a series of measurement techniques traditionally used to determine changes in material properties with temperature. No other techniques have proved more useful than thermal analysis in the material characterization. The observation of the behavior of materials and the quantitative measurement of the change on heating deliver a great deal of useful information on the nature of the material. As a result thermal analysis has been used in many areas of basic and applied research production and quality control in the material science especially polymer and polymer composites. This paper describes the application of thermal analysis techniques in the design optimization technical support and QA/QC of polymer and polymer composites. The results illustrate the value of termal analysis for characterizating polymeric materials.
For more than forty years since its introduction carbon fiber composites have remained an elusive material in the automotive industry. Proven in jet fighters and high-end race cars for over 20 years there is little doubt about its ability to build lighter more durable vehicles. Offering a weight savings of 75 percent over steel carbon fiber gives sports cars a real advantage in acceleration and top speed and enables all automobiles to achieve improved fuel economy. Commercialization continues to be hindered by high material and processing costs and slow production rates. In spite of these obstacles more than 25 series production vehicles will feature carbon fiber composites in 2004 fueled by advances in manufacturing technology new material forms and steadily declining material costs. This paper presents the current state of carbon fiber use in automobiles in Europe North America and Japan ranging from the exotic “supercars” to niche producers and the major automobile manufacturers. Carbon fiber applications include body panels structure and functional components. Advances in processing techniques will be reviewed with a focus on what is being done today and what still needs to occur to economically move beyond volumes of a few thousand parts per year and into more mainstream vehicles.
Development of the carbon/epoxy body panels and structural components of the Lamborghini Murcièlago is discussed while use of aerospace grade technology and materials is justified for this particular application. Laminate design and stacking sequence is reviewed and the use of woven fabrics over directional tape is motivated. Engineering solutions for tooling operations in order to achieve class A surface certification are analyzed. Design for environmental aging as well as accelerated degradation tests are described. Hybrid adhesive bonding as sole method of joining the composite body components to the tubular steel chassis is reviewed.
This paper will review the development and design of the DaimlerChrysler 4.7L V-8 engine. The new plastic cover module comprised of a glass reinforced vinyl ester thermoset was developed in just 12 months and replaces a magnesium component. Significant cost savings were realized while incrementally improving noise vibration and harshness (NVH). Extensive finite element analyses (FEA) including mold filling analysis and anistropic property calculation were utilized to ensure robust system performance. This collaborative effort eliminated the prototype step for the cover housing which in turn reduced development time and cost by allowing the component to move directly from design to production. This capability also allowed NVH improvement to be realized over the already favorable acoustical performance of the previous die-cast magnesium component.
When INOPLASTIC OMNIUM the Joint Venture between PLASTIC OMNIUM AUTO EXTERIEUR and INOPLAST was born in 1998 its production of composite liftgates and trunks was 400 parts / day. In 2000 IPO produced 800 liftgates / day and this expansion went on to reach 2500 parts produced daily in 2003. In the same time other Tier 1 suppliers had a similar growth: in 2000 3.2 % of European liftgates were made of plastic whereas they are 4.7 % in 2003 and this number is still growing. This evolution raises the question: “why is the use of composite rear closures so interesting?”. The composite solutions for rear closures present several technical economical and industrial advantages. We will highlight some of those advantages in this paper and illustrate them on precise examples coming from the experience of IPO on its current productions: Weight reduction Antenna interior trim and exterior cladding integration 15 kph insurance rear impact management Capital investment reduction OEM industrial management: cycle time improvement and harmonization. We will also show how the new improvements of automotive Tier 1 suppliers on closure function and on materials & processes can bring composite liftgates and trunks new advantages.
The automotive industry has long sought new materials for exterior body panels. Metals are heavy easily dented many corrode and all require complex tooling to meet today's styling requirements. Thermoplastics offer good impact strength design freedom Class-A finish and cost effectiveness but lack stiffness and strength for truly structural applications. Thermoset composites are lighter stiffer and have simpler tooling than metals or injection molded thermoplastics but require extensive secondary-finishing operations to achieve Class A. Thermoplastic composties offer significantly higher stiffness and strength than unreinforced thermoplastics but cannot provide a glossy Class-A surface although they have long been used in applications where a grained first surface is acceptable. This paper reviews innovative work on a 2-layer body-panel system incorporating a new lighter weight structural thermoplastic composite backside and an aesthetic surface layer-either precoated aluminum or inherently colored thermoplastic or paint films- to meet aesthetic requirements. Topics to be covered include materials molding and target applications.
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