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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The Development of DFT Long-Fiber Thermoplastic Composite Soft-Top Headers
In your father’s car all of the significant body structures were made from metals. Today composites are increasingly used to produce more and more demanding structures. In concept vehicles such as the Daimler- Chrysler CCV and ESX3 composites are the structure. In production vehicles pick-up boxes floor pans front-end carriers closure panels skid plates and many other structural applications are made from composites. Direct Feed Thermoplastic (DFT) composites have been used to produce several automotive structures including front-end carriers seat bases and convertible soft-top rails and headers. In this last application soft-top headers DFT composites successfully displaced steel and SRIM composites on the basis of relative cost and performance. Like most technology substitutions the process of developing the DFT header was lengthy taking over five years from concept to production. This development process along with the DFT manufacturing technology and the benefits that it imparts to soft-top headers are described in this paper. The paper demonstrates that DFT when used appropriately offers an unparalleled combination of performance aesthetic and economic benefits.
Properties of Thermoformed Low Density Glass Reinforced Thermoplastic Sheet
The thermoformability of low-density polypropylene sheets reinforced with long discontinuous glass fibers was assessed using a laboratory scale thermoforming machine. The effects of material parameters (glass fiber loading and sheet basis weight) and processing parameters (sheet temperature and pressure) on part thickness glass fiber distribution and mechanical properties were evaluated. The results indicate that for the parts studied pressure assist is required for thermoforming. Part characteristics were observed to be reproducible and constant over a wide range of sheet temperatures and pressure assist levels. The mechanical properties of the thermoformed sheets were assessed using flexural testing. The modulus and strength values observed were comparable to properties obtained on compression molded samples of the same thickness.
Thermoplastic Composite Sandwich Panels
Thermoplastic composites are attractive for automotive applications since they can be rapidly formed into low cost complex structures with good impact strength and flexural rigidity. The properties of these composites can be enhanced while reducing basis weight through the use of sandwich structures. This paper will illustrate the extent of enhancement achieved through the use of thermoplastic composite skins combined with lower density thermoplastic cores. Glass mat reinforced polypropylene (GMT) with a thickness of 3.8 mm and a glass content of 40 wt % will be used as a baseline for assessing the performance of sandwich panels. Skins will include GMT as well as aligned fiber reinforced laminates. Both honeycomb and foam cores will be evaluated. Flexural rigidity will be presented and impact properties will be based on instrumented drop impact testing.
The Effect of Reinforcing Fiber Length on Surface Properties of Thermoplastic Composites Made by Surface Finishing / Compression Molding
The Valyi SFC (surface finishing/compression) molding TM process was used to evaluate the effects of fiber length on the important performance properties required for class A thermoplastic composite panels. Class A moldings for automotive exterior use must meet demanding visual performance and demanding structural properties. The benefits of long fiber reinforcement in SFC molding have been reported. The long fiber reinforced PP resins show enhanced stiffness and impact strength. Fiber length degradation in the SFC process is minimal. This paper reports on the surface properties of polypropylene composites made with short and long fibers. Surface read through of the fiber reinforcement is examined and methods for improvement are discussed. The SFC process combines resin extrusion film finishing and compression molding in one low pressure molding process. In this process a finishing film is placed over a mold cavity resin is extruded over the film from a traversing “coat-hanger” die and the mold is closed to form and finish the part in one step. This process has been successfully used to mold full-scale vertical and horizontal panel composites.
Stamping of Woven Fabric Reinforced Thermoplastic Composites
This study is to investigate the feasibility of shaping preconsolidated woven fabric reinforced thermoplastics using sheet hydroforming as being a new forming method for composite manufacturing. For that purpose a new constitutive model has been developed based on a homogenization method considering the microstructures of composites including mechanical and structural properties of fabric reinforcement. The current model aims to account for the effect of the fiber strength difference and orientation on anisotropy and also to simulate shear deformation with no length change which is common in FRT composite forming. For validation purposes the developed model was implemented in an explicit dynamic finite element code and tested for several deformation modes including pure shear as well as three-dimensional deformation mode
Bio-Composite Materials as Alternatives to Petroleum-Based Composites for Automotive Applications
Natural/Bio-fiber composites (Bio-Composites) are emerging as a viable alternative to glass fiber reinforced composites especially in automotive applications. Natural fibers which traditionally were used as fillers for thermosets are now becoming one of the fastest growing performance additives for thermoplastics. Advantages of natural fibers over man-made glass fiber are: low cost low density competitive specific mechanical properties reduced energy consumption carbon dioxide sequesterization and biodegradability. Natural fibers offer a possibility to developing countries to use their own natural resources in their composite processing industries. The combination of bio-fibers like Kenaf Hemp Flax Jute Henequen Pineapple leaf fiber and Sisal with polymer matrices from both non-renewable and renewable resources to produce composite materials that are competitive with synthetic composites requires special attention i.e. biofiber- matrix interface and novel processing. Natural fiber reinforced polypropylene (PP) composites have attained commercial attraction in automotive industries. Needle punching techniques as well as extrusion followed by injection molding for natural fiber–PP composites as presently adopted in the industry need a “greener” technology-- powder impregnation technology. Natural fiber–PP or natural fiber–polyester composites are not sufficiently eco-friendly due to the petro-based source as well as non-biodegradable nature of the polymer matrix. Sustainability industrial ecology eco-efficiency and green chemistry are forcing the automotive industry to seek alternative more Eco-friendly materials for automotive interior applications. Using natural fibers with polymers (plastics) based on renewable resources will allow many environmental issues to be solved. By embedding bio-fibers with renewable resource based bio-polymers such as cellulosic plastic corn-based plastic starch plastic and soy-based plastic are continuously being developed at Michigan S
Approaches to Clay Nanolayer Reinforced Thermoset Epoxy Polymer Nanocomposites
Montmorillonite clay - diamine intercalates were used for the formation of glassy thermoset epoxy – clay nanocomposites. The intercalated alpha-omega polyoxypropylene diamines (Jeffamines) played the dual role of organic modifier and curing agent. Depending on the chain length the intercalated diamines adopt different configurations inside the clay galleries resulting in basal spacings from ~14 Å (lateral monolayer) to ~45 Å (folded structure). Accordingly non-intercalated and exfoliated (nano)composites were formed with improved mechanical properties. From a mechanistic point of view they offer the optimum environment for enhanced intragallery polymerization by eliminating the effect of dangling alkyl chains in the polymer’s matrix and by utilizing the catalytic activity of both onium ions of each diamine molecule. The use of the primary diamines as organic modifiers of the H+-clays afford an in situ functionalization of the inorganic clay as part of the curing process of thermoset epoxy polymers reducing the cost and time for nanocomposite fabrication.
Increasing the Impact Resistance of Short Glass Fiber Reinforced Vinyl Composites
The addition of short glass fibers to thermoplastic materials is known to significantly reduce the impact properties of the resulting composites. This paper is the third in a series devoted to understanding and improving the impact strength of short glass fiber reinforced vinyl composites. The first paper characterized the impact behavior and failure mechanisms of these materials. The second paper examined methods of increasing the impact resistance using semi-rigid capstock laminates. The current paper extends this work to laminates using rigid vinyl layers to achieve higher impact strength. Instrumented drop weight impact results demonstrate improvements up to four times that of the original composite.
The Economical Performance of Long Glass Reinforced Polypropylene Concentrates
Long glass fiber reinforced polypropylene (LGF PP) has generated significant interest in the automotive industry over the past several years. With increasing emphasis on cost reduction part consolidation reduction in total assembly cycle time and recyclables this versatile material offers many benefits. To provide these solutions while considering (improving) the economics required in the automotive structural large part segment LNP has introduced a highly loaded LGF PP concentrate. This paper will first discuss the industry trends that are driving tremendous growth potential in LGF PP. This brief overview will address the evolution of LGF PP materials and components in the vehicle and market pressures driving the need for a more cost effective material approach. The cost reduction potential of LGF PP concentrate blends will be illustrated along with the mechanical property performance and other specific benefits of this masterbatch concept. A study of impact-enhanced blends will also be reviewed
LFT-D-ILC - Innovative Process Technology Decreases the Costs of Large-Scale Production of Long-Fiber-Reinforced Thermoplastic Components
Long-fiber-reinforced thermoplastics (LFT) have gained an increasing market share in the European automotive industry. In some large-scale applications the processing of semi-finished products such as LFT-GMT (glass-mat reinforced thermoplastic sheets) and LFT-G (long-fiber-reinforced thermoplastic granulate) is already known. The LFT-D process in which continuous rovings are fed directly into the polymer melt differs fundamentally from the LFT-GMT and LFT-Pellet-Process. High economic efficiency is achieved when the cost intensive production of semi-finished products as well as the subsequent logistic costs are avoided. Thermal stress of the compound is minimized. Excellent flow properties as well as consistent glass fiber content are obtained. The degree of freedom regarding the use of new polymer blends and different types of fibers for example natural fibers enables an individual matching of the compound according to the specific needs of the application. In addition the glass fiber content can be adjusted as needed. The solution presented in this paper is based on the Dieffenbacher Direct Process (LFT-D-ILC). This development is responding to the technical requirements of automotive parts for large-scale production. As the leading manufacturer of presses and fully automated press lines for the production of components of fiber-reinforced materials such as SMC BMC LFT-GMT LFT-P and LFT-D-ILC Dieffenbacher offers complete technical solutions to suppliers and the automotive industry.
Characterization of Adhesive Failure and Modeling for Dynamic Analysis
One of the ways of increasing fuel efficiency of a typical automobile is to reduce its overall weight. To this extent plastics especially fiber reinforced plastics are finding an increasing role as automotive structural components. The automotive structural systems made up of these structural fiber reinforced plastic components should satisfy the needs in terms of safety strength NVH and durability in addition to being affordable manufacturable with desired fit and finish and recyclable. In general structural components made up of fiber reinforced plastics are adhesively bonded together to form structural systems capable of carrying automotive structural loads under static and dynamic conditions. Fiber reinforced plastics and the adhesive used to bond them to form a structure are inherently viscoelastic in behavior. It is imperative therefore to understand the behavior of these adhesively bonded fiber reinforced plastic components in terms of their load carrying capacity at different temperatures and different load or strain rates. One of the key factors in this understanding is to characterize the adhesive failure itself at different temperatures and different strain rates of loading. The present paper is an attempt to present some results from an ongoing research work on fiber reinforced adhesively bonded large injection molded thermoplastic automotive structural systems. In particular the paper presents the results from the test methodology and the mathematical models used to characterize the failure mechanics of adhesively bonded automotive body sections at different temperatures and different load or strain rates.
Development of Low Density GMT Composites for Automotive Applications
The development in the field of composites has been spurred by the need for lightweight fuel-efficient automobile that is environmentally friendly and affordable. A low density light weight GMT composite containing long chopped fiber strands was developed by AZDEL Inc. for use in headliner and other automotive applications. The low density GMT (LD-GMT) is available in grades ranging in basis weight of 600 to 2000 g/m2. This paper presents development of this LD-GMT material for automotive interior and structural applications. This thermoformable material has several advantages over other traditional materials like steel and thermoset composites. The LD-GMT offers design flexibility low weight high rigidity excellent energy absorption characteristics faster cycle times and an environmentally friendly manufacturing process. The design flexibility and application of these LD-GMT composites in automotives and the advantages of applying these composites over the other materials in interior structural and modular applications will be discussed.
The Effect of Sample Preparation on the Flexural Strength of Reinforced Nylon 66
Cutting flexural test specimens from molded plaques is commonly used in material testing. The mechanical properties of these cut specimens may be affected by the cutting process as it could introduce extrinsic flaws and thermal residual stress on the cut surfaces. The objective of this experimental research is to determine how band saw cutting affects the flexural strength of 33% short glass fiber reinforced nylon 66. The specimens for the flexural test were obtained by cutting molded plaques using different blade types blade speeds feed rates and levels of polishing. The results were compared with those from uncut specimens. Surface morphology of specimens’ cut edges was observed by using Scanning Electron Microscopy. The results indicate that lowest strength of cut specimens is achieved at the lowest blade speed and highest work piece feed rate.
Experimental and Numerical Study of Stamp Thermo-Hydroforming for Shaping Glass Mat Fiber Reinforced Thermoplastic Sheets into Hemispherical Cups
The goal of this study was to verify through experimentation and numerical modeling that the stamp thermo-hydroforming process provided a suitable alternative to conventional methods such as thermoforming and stamp forming as a means for processing thermoplastic materials. Hydroforming involved supporting the thermoplastic sheet with a bed of viscous fluid that applied a hydrostatic pressure across the part during forming. The external support provided a through-thickness compressive stress that delayed the onset of tensile instabilities as well as reduced the formation of wrinkles due to tensile frictional forces. Preliminary experiments were conducted using a procedure that was designed and built in-house. Initial experiments focused on a fluid pressure applied from one side of the draw blank material. Evaluation included pure stretch experiments experiments where the material was allowed to draw and experiments conducted under a combination of draw and stretch. Complications arose during the experimentation but the benefits of a localized hydrostatic pressure were demonstrated including a 7-10% increase in draw depth for the thermoplastic sheets. The numerical analysis conducted using MARC showed results that correlated with the experimental trends. Overall the experimental results coupled with the numerical modeling showed that the stamp thermo-hydroforming process was a viable processing method for thermoplastic materials that warrants additional attention based on the significant advantages in cost savings and part production accuracy.
Continuous Fiber Reinforced Thermoplastic Composites in The Automotive Industry
Composite materials continue to gain popularity in the automotive community primarily due their ability to reduce weight. Other key advantages include function integration corrosion resistance and low cost tooling. Although thermoplastic composite products have been commercially available for some time now new products specifically continuous fiber reinforced thermoplastics are spurring engineering activity in this growing segment of the composites industry. This paper serves to review materials technologies and applications of continuous fiber reinforced thermoplastics in the automotive industry. Specific application areas include underbody protection bumper beams and load floors.
Development of Low Density GMT Headliners with Improved Acoustical Performance
Low-density GMT (glass mat thermoplastics) materials are being used increasingly in automotive interior applications. These composites have found wide acceptance amongst various automotive OEMs for overhead systems. The superior mechanical properties availability in various basis weight grades ease of processing and ability to be molded to differing thickness makes the AZDEL SuperLite a versatile material for both structural and non-structural headliners. In this paper we have presented the acoustical performance of these low-density composites. Various combinations of this headliner substrate with face fabrics and covering materials were made and their normal incidence sound absorption coefficient was obtained according to ASTM E1050 test method. By varying the areal density molded thickness and the types of skins on the surface of the composite the porosity and the airflow resistance can be tailored to provide optimal sound absorption across a broad range of frequencies. The effect of these factors and their interactions are discussed.
Structural Mechanics of Polymer Coated Optical Glass Fibers: Review
The paper contains a brief review of the state-of-the-art in the stress-strain analysis (Structural Mechanics) of polymer coated optical glass fibers, with an emphasis on the analytical modeling.
Kinetics of Isothermal Crystallization of Syndiotactic Polypropylene: Avrami and Urbanovici-Segal Analyses
In this paper, the Avrami and Urbanovici-Segal macrokinetic models were applied to describe the kinetics of isothermal crystallization from the melt state of syndiotactic polypropylene (sPP). Data analysis was carried out using a direct data-fitting procedure, in which the experimental data were directly fitted to each macrokinetic model using a non-linear multi-variable regression program. The results suggested that the Urbanovici-Segal model was the better of the two in describing the isothermal crystallization data of sPP.
Production of Structures from Thermoplastic Composite Towpregs
An efficient and cost effective way of producing continuous fibre-thermoplastic matrix composites relies on the use of towpregs. Equipments are being developed for the production of the towpregs and also to manufacture pultruded profiles and filament winding structures. The properties of the composite products are determined and compared with conventional alternatives. An assessment is made on the influence of the processing conditions on the output and mechanical properties of glass fibre/polypropylene (GF/PP) composites.
Friction Properties of Thermoplastics in Injection Molding
In the ejection stage of parts injection molded over cores the knowledge of the friction properties between the mould surface and the part are important to optimize the ejection system solution. The coefficient of friction depends strongly on the mould surface and the temperature at the moment of ejection. Prototype equipment was developed to measure the friction properties in as-molding conditions, and methods developed to perform the testing. Data will be presented for two thermoplastics (polycarbonate and polypropylene).
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