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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Integration of Features into Parts Made from Thermoplastic Unidirectional Tape — Overview and Case Study
Thermoplastic composite materials have lately been considered increasingly for application in structural components. Especially semi-finished products with continuous fiber-reinforcement such as woven fabrics or unidirectional tapes have a high potential to increase part performance significantly. However due to their limited drapability and flowability the forming of highly complex structures such as ribs is not feesible. This paper presents an overveiw of desired features that are commonly part of complex technical applications. It shows how implementation of those can be achieved with continuous-fiber-reinforcement structures by combining them with short and long fiber-reinforcement material. The subsequent case study presents a related investigation on overmolding of unidirectional tape inserts. In conclusion an outlook is given on how these results can be transferred to more complex components.
Program Summary of the ACC Automotive Composites Underbody
A structural composite underbody capable of carrying crash loads has been designed fabricated assembled into a structure and tested by the Automotive Composites Consortium. The underbody is compression molded of sheet molding compound (SMC) with a vinyl ester matrix and predominately glass fabric reinforcement with some chopped glass. CAE-based design methodologies were utilized to assess the structural stiffness and impact performance of the initial composite underbody design. Weld bonding was selected as the means to join the composite underbody to the steel passenger compartment. A method for weld bonding the structural composite has been developed and tested in static and dynamic modes. The molded underbody was tested in modal bending and torsion. The underbody was assembled into a structure mimicking an automotive body-in-white and tested to simulate an offset deformable barrier crash. The Automotive Composites Consortium (ACC) is a joint program between GM Ford Chrysler and is funded in part by the United States Department of Energy.
Manufacturing Scenarios & Challenges with a Fabric SMC Automotive Underbody
Compression molding of fabric SMC in steel tooling is a cross between prepreg molding and regular sheet molding compound (SMC) molding. Material processing differences such as minimal material flow represent major manufacturing challenges requiring different approaches for production operations. This paper will present the observed challenges and potential approaches that will enable cost effective manufacturing scenarios. Aspects of the processing include (but are not limited to) SMC compounding charge cutting charge placement tool loading edge filling of the part wrinkles and overlaps part trimming modeling and material testing. Presented will be solutions we utilized in addition to studies and cost models used to alleviate some concerns.
Enabling Faster Resin Infusion Processing of Automotive Composites: A Nano-Nectar" Technology Leading Epoxy to High Performance and Low Viscosity "
Graphitic carbon nanofibers (GNFs) were first made into a “nano-nectar” which is “liquid nano-reinforcement” (LNR) with reactive nanofibers (r-GNFs). Due to the uniform dispersion of r-GNFs in the LRN simply mixing the LNR with an epoxy led to a nano-modified epoxy with uniform dispersion of nanofibers a so-called nano-epoxy. More importantly the nanofibers were involved in the cross-linking structures of the epoxy through covalent bonding between the epoxy matrix and the nanofibers. Results showed that the nano-epoxy possesses dramatically reduced viscosity and enhanced multiple mechanical and thermal performances by simply mixing two kinds of liquids: a very small amount of LNR functioning as a “nector” and a base epoxy matrix. The simplicity of the “nano-nectar” approach leading to reduced viscosity (e.g. 50% lower than the pure epoxy) can lead to faster Resin Infusion processing for automotive composite manufacturing due to reduced power requirements for flow and part consolidation.
Material Properties of a Fabric Sheet Molding Compound for a Structural Composite Underbody
The Automotive Composites Consortium (ACC) has selected a fabric sheet molding compound (SMC) as the main material and process system for a structural composite underbody. This Paper describes the properties of this SMC material including tensile compression and flex. Thermal properties including coefficient of linear thermal expansion and Tg temperatures were determined. The effect of two different fabric weights and several layups thicknesses and molding parameters is also reported. Overlap and butt joints within the layup were compared. The Automotive Composites Consortium is a joint program between General Motors Ford Chrysler in partnership with the United States Department of Energy.
Double Dome Structural Test—Analysis Correlation Studies
Computer-aided engineering-based design methodologies have been utilized throughout the Automotive Composites Consortium Focal Project 4 to assess the vehicle level structural stiffness and impact performance of the composite underbody design proposals and to estimate the potential mass reduction for several candidate material scenarios. To increase confidence in the vehicle-level model predictions and to better understand the effect of fabric draping on fiberglass fabric Sheet Molding Compound composite material properties several quasi-static structural “double dome” component tests were simulated for the purpose of test-analysis correlation and modeling methodology development.
Fatigue Performance of SMC Composite Material Under Different Environmental Damage & Temperature Conditions
The Automotive Composites Consortium (ACC) a partnership of Chrysler Group LLC Ford Motor Company General Motors Company and the U.S. Department of Energy conducts pre-competitive research on structural and semi-structural polymer composites to advance high strength lightweight solutions in automotive technology. An ACC focal project concerning the development of a structural composite underbody was established to provide methodologies and data for each ACC member company to implement lightweight cost-effective structural composites in high volume vehicles. This objective will be fulfilled through design analysis fabrication and testing of a structural composite underbody. A key design element required for implementation of the underbody structure is an understanding of the affects of environmental temperature and impact damage on the axial fatigue performance of the SMC composite material selected for the underbody structure fabrication. Research efforts have been made on fatigue performance of different type of composite materials (Ref. 1-5). In this study specimens were tested with no damage as well as two levels of impact damage. Environmental temperatures for the undamaged specimens were -40°C 21°C and 80°C. It was observed that fatigue life increased at low temperature conditions and decreased at high temperatures. The affect of temperature had a greater influence on fatigue life than the impact damage in this study. Temperature increases as measured at the specimen surfaces were observed as test frequency increased. Similar observations were made by Bellenger et al (Ref.6). The relationship between stress loading frequency and temperature will be investigated. Optical and scanning electron microscopy will be used to examine the crack locations and characteristics for specimens tested under different conditions.
Shear Deformation Properties of Glass-Fabric Sheet Molding Compound
In the current phase of the Automotive Composites Consortium structural composite underbody project a draping analysis of a full underbody made of woven glass-fabric sheet molding compound (SMC) was used to identify changes in local mechanical properties due to fabric shearing during compression molding. As a laboratory-scale effort woven glass-fabric SMC was compression molded into double-dome shapes and flat plaque configurations of three separate 4-ply layups. Double domes underwent static crush impact and mechanical testing; mechanical properties were further compared to corresponding flat plaque properties. All data was used to broaden the material property database and validate model predictions of strand orientations in a molded part.
Local Continuous Fibre-Reinforcement — Tailored Injection Moulding >>Lightweight Potential for Injection Molded Parts<<
Weight reduction of components is becoming increasingly important for example in automotive applications where significant fuel savings and CO 2 emission reduction can be made. In many cases metal load - bearin g parts can be replaced by short or long fib er reinforced thermoplastics. These composites have become an integral part of industrial large scale production especially due to their economical processability and increased functionality. The limited mechanic al properties such as stiffness and impact strength prohibit the use of injection moulded parts in higher load - bearing applications. Furthermore the viscoelastic behavior of the matrix at high temperature or at permanent load is a disadvantage (tendency to creep). Local continuous fib er reinforcement can overcome these disadvantages by increasing the properties and reducing tendency to creep. The technology of continuous fiber reinforcement with thermoplastic materials includes in principal all pre - impreg nated fiber structures like woven and non - woven fabrics UD - strands tape layups or winded geometries. To characterize the effect of unidirectional fiber reinforcement in this research work a single pre - impregnated fiber strand was chosen. These strands we re then being manufactured to generic specimens in a specialized mould for insert technology with a standard injection moulding process a s one of the most important processing technology for thermoplastic polymers . The mechanical behavior of the parts acco rding to the variation of material and process parameters were analyzed with a static tensile test and a dynamic - mechanical analysis (DMA).
Selective Compatibilization for Stiffer High Impact TPO / Clay Nanocomposites
Different compatibilization strategies from master batch mixing using a twin-screw extruder with various coupling agents were investigated to improve the stiffness of nanocomposites based on a high impact TPO (n-Izod > 600 J/m) with 2% and 4% of organoclay content. Three coupling agents based on grafted maleic anhydride polymers (gMA) were used to tailor the compatibility of the organoclays to either or both the rubbery domains and the polyolefin matrix. A detailed microstructural of the different nanocomposites revealed the preferential presence of organoclays in the rubbery domains the matrix or both depending on the masterbatch sequential compounding strategy i.e. the type of coupling agent(s) mixed with the type of organoclay. As anticipated the presence of organoclays in both the matrix for improved tensile properties (Young’s modulus and stress and strain at yield) and in the rubbery domains for higher impact resistance (n-Izod at 0 and 23°C and flat sheet impact at -40°C). A control experiment on a blend of PP and an ethylene-propylene copolymer with a PPgMA coupling agent and organoclay compounded in a similar fashion led to the usually improved tensile properties but reduced impact resistance. In this case the organoclay was found present in the matrix only as the coupling agent used could not compatibilize the organoclay to the copolymer phase. It is concluded that organoclays act on the rubbery phase to increase its toughening effect in the TPO presumably by increasing the cavitation stress of the TPO.
Synthesis of Bipolar Plates for Fuel Cells Based on Exfoliated Graphene Nanoplatelets Filled Polymeric Nanocomposites
The objective of this research is to investigate the potential of using exfoliated graphene nanoplatelets (GNP) as the conductive filler to construct highly conductive polymeric nanocomposites to substitute for conventional metallic and graphite bipolar plates in the polymer electrolyte membrane (PEM) fuel cells. High density polyethylene (HDPE) was selected as the polymer matrix and solid state ball milling (SSBM) followed by compression molding was applied to fabricate HDPE/GNP nanocomposites. Results showed that HDPE/GNP nanocomposites made by this method exhibited excellent flexural properties and low gas permeability with GNP loadings up to 60wt% which successfully meet the DOE requirements for bipolar plates. However it was found that using GNP alone as a single conductive filler was insufficient to achieve the required electrical conductivity (>100 S/cm). Combining GNP with a minor second conductive filler such as carbon black (CB) and carbon nano-tubes(CNT) could substantially enhance the electrical conductivity of the resulting nanocomposites. At the same time the processing time of SSBM is considered as a crucial parameter in optimizing the various properties of the final nanocomposites. It is believed that the bipolar plates made from HDPE/GNP nanocomposites will allow lighter weight of PEM fuel cells with enhanced performance which is particularly suited for automotive applications.
Thermoplastic vs. Thermoset Matrices for High-Temperature Out-of-Autoclave Composites Applications
The high-temperature high-mechanical performance end of the composite materials spectrum–so-called advanced composites–has long been dominated by thermoset matrices primarily epoxy and urethane chemistries with carbon or aramid continuous-strand unidirectional fiber or fabric weave reinforcements. However that is starting to change as thermoplastic resin suppliers begin to investigate and more aggressively position their own high-temperature offsets in this segment–not just as lower cost lower weight faster processing replacement for thermosets but as direct metal replacements themselves. By offering molders and OEMs the option to produce performance parts with higher productivity thermoplastic matrices that do not need to be polymerized in the tool numerous benefits are gained including reducing cycle times volatile-organic compound (VOC) emissions energy consumption spoilage and finishing steps–all of which help drive down costs and make advanced composites more affordable for higher volume applications than metals. This can be particularly attractive for processors without autoclaves or without sufficient auto clave resources to process traditional high-performance thermoset composite matrices or where producing parts via these or other traditional thermoset processes are difficult and/or costly. This paper will provide an overview of current market pressures supporting the growth of high-performance thermoplastics and then will review various processing options for both thermoset and thermoplastic high-performance composites. Next several short case histories involving conversions to thermoplastic matrices directly from metals will be presented. Lastfuture trends that could impact this segment will also be considered.
Mechanisms of Interfacial Adhesion in Metal-Polymer Composites
Hybrid materials featuring thermoplastic polymer composites in conjunction with metals can be used as structural materials in commercial tr ansport and military vehicles and for protection of buildings and infrastructure. C onstituent thermoplastics and metals have distinct advantages as protective materials however metals on their ow n are heavy hence hybrid materials offer option as lighter materials. This study focuses on the effect of surface treatments to improve adhesion between dissimilar materials such organic polymers with metal reinforcement materials. Surface energy was found to possess a direct relationship with the amount of polar groups on the surface of a modified polymer and free radicals on the metal surface. Higher surface energy correlates with superior interface adhesi on. This work establishes the ba sis that polar groups and free radicals improve adhesion between polymeric (thermoplastics) and metallic surfaces.
Super Lap Shear Joint Structural Test—Analysis Correlation Studies
Computer-aided engineering-based design methodologies have been utilized throughout the Automotive Composites Consortium Focal Project 4 to assess the vehicle level structural stiffness and impact performance of the composite underbody design proposals and to estimate the potential mass reduction for several candidate material scenarios. To increase confidence in the vehicle-level model predictions and to better understand the effect of temperature on hybrid composite-to-metal joint performance quasi-static structural joint coupon tests were simulated for the purpose of test analysis correlation and modeling methodology development.
TILTING DIE | THE CONVINCING NEW SOLUTION TO CENTRE AN ANNULAR DIE
A totally new solution was developed to centre the die in regard to the mandrel of an annular die. The tilting technology overcomes most of the drawbacks of the existing conventional centering solutions. The new tilting technology can be easily retrofitted to existing heads for pipes | for blown films and for the extrusion blow molding process. Tilting dies enable to further reduce remaining eccentric thickness differences in the extruded products. So they help to improve the quality of the products while in the same time the cost of the production is reduced.
High Performance EVOH Nanocomposites of Interest in Packaging Applications
EVOH are materials with broad application in high barrier packaging due to transparency and superior oxygen barrier. However | these materials suffer from strong plasticization in properties due to sorption of moisture | which handicaps their application under high moisture conditions such as those applied in many packaging cases. This paper shows the development of novel nanocomposites based on an optimized kaolinite grade | commercially marketed as O2Block® | which exhibit enhanced UV and gas barrier and decreased water permeability and sensitivity.
THE EFFECT OF COMPOSITION AND PROCESSING PARAMETERS ON THE MORPHOLOGY AND PROPERTIES OF PC/ABS/ORGANOCLAY NANOCOMPOSITES
In this study | blends based on poly(acrylonitrile-butadiene-styrene) (ABS) and polycarbonate (PC) were prepared and studied | in an attempt to explore the performance of mixtures deriving from recycling of waste electrical and electronic equipment (WEEE). The modification of ABS and ABS/PC blends via the incorporation of reinforcing fillers | such as organic modified montmorillonite nanoparticles (OMMT) | was also explored and its effect on the structure and properties was evaluated.
Failure Analysis of cracking HDPE cartridges. Optimization of Molding process using Dr. Taguchi Method of D.O.E.
This paper’s goal is to explain how to achieve the optimum molding conditions that minimize the effect of stress cracking without removing the causes of degradation during service use. Analyzing failure of HDPE caulking cartridges: due to premature initiation of cracking and brittleness at the cartridge wall.
LATENT ACID CATALYSTS FOR THERMOSET PROCESS CONTROL IN ADVANCED COMPOSITES
Bac2 has developed a storage stable | molding material | incorporating a latent acid catalyst for the compression molding of advanced composite bipolar plates | key components of fuel cell stacks. The latent acid catalyst technology is used to control the reactivity of phenolic resins and furan bio-resins | by-products from plant sources. The process control imparted using the hydroxylamine based latent catalyst has extended the opportunity to use phenolic and furan binders in wider composite and adhesives applications.
MULTIBLOCK POLYESTER ELASTOMERS/ZINC OXIDE COMPOSITES: PREPARATION AND CHARACTERIZATION
In this study, composites were obtained by introducing the zinc oxide (ZnO) fillers into the block copolymers of poly(butylene terephthalate) (PBT) and poly(tetramethylene oxide) (PTMO) by melt compounding method. The thermal conductivity and coefficient of thermal expansion of composites were investigated as a function of ZnO size and concentration. It was found that addition of ZnO increased thermal stability, while it decreased coefficient of thermal expansion of the composites at low temperatures (55 to 70 °C).
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