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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In the steady quest for lightweighting solutions continuous carbon fiber composites come down to the ground serving now not only the aerospace but also the automotive industries. This category of carbon fiber-reinforced plastics (CFRP) has recently taken a step in car body structures for its high stiffness and strength. Continuous carbon fiber composites are much more complex than metal with respect to failure in particular. This presentation will cover the application of micro-mechanically-based progressive failure models to simple demonstrator structures such as coupons.
In Part 4 of this multiyear study the relationship between the polypropylene long-fiber thermoplastics (PP LFT) and the processes used to mold are presented. Parts are formed by injection molding compression molding and plunger tool using the same formulation in the PP LFT part. The effects of glass-fiber diameter sizing and changes in molding conditions were explored. Prior work showed significant differences between injection molding and compression molding. The use of the plunger tool has given a unique opportunity to evaluate the effects of molding conditions and fiberglass products on the final part performance.
The bulk properties of long (> 1mm) fiber-reinforced composite materials are highly governed by the orientation of the embedded fibers within the matrix which depends on processing conditions and mold design. Modeling the orientation of long fibers in molding processes is typically carried out using the Folgar-Tucker equation for rigid rod-suspensions which is a modification of Jeffery’s equation for suspensions of prolate spheroids. In the first part of this paper we report our efforts to extend the traditional method of ellipses for measuring fiber orientation to systems of long glass fibers. In the second part we evaluate an alternative model for predicting the orientation in long fiber composite materials which allows the effect of bending to be taken into account during processing in both shear and shear-free flow fields. Simulation of fiber orientation in injection molding using the new model is compared against experimental data showing significant improvement in the predictions relative to those based on using the conventional model for rigid fibers.
An introduction and general overview of the manufacture of fiberglass reinforcements is presented. Included is a general discussion of the role and components of the chemical coating on the glass fibers known as the sizing and why these chemicals are important to the manufacture and final properties of composites. This presentation explains what sizing is how it affects composite properties how it is applied to glass what classes of sizing chemicals are used and what each component does and why it is needed. The goal is to help the fiberglass industry educate customers and debunk the myth that all fiberglass is the same.
This presentation will discuss the various dry fiber preforming methods that can be used with the many iterations of liquid composites molding processes (e.g. resin transfer molding (RTM) vacuum-assist RTM (VARTM) liquid compression molding high-pressure injection molding etc.). The evolution of dry fiber processing methods will be shown as will the changes in binders the importance of binder selection and the evolution in mechanization of preforming. Many photos will be shown of the various types of preforming equipment with discussion of each dry fiber preforming method process options and how they relate to the types of reinforcing materials applications properties and production rates achieved. It will be shown how application material and production requirements drive selection of the dry fiber preforming process. The pros and cons of each dry fiber preforming process will be discussed to provide guidance for process selection based on the design requirements of an application material selection and production requirements. For structural applications complex dry fiber preforming will be shown for complex laminate schedules with mixtures of reinforcing materials such as engineering fabrics woven materials and unidirectional fabrics in complex fiber alignments. The use of inserts and core materials with complex dry fiber preforms also will be shown and discussed. Last the pros and cons of the need for net-shape dry fiber preforms for high volume applications and structural applications will be discussed with examples and pictures.
The tensile strength of a composite is dependent on the properties of the fiber the properties of the matrix resin the fiber content the geometry and orientation of the fibers and the interfacial strength between the fiber and the matrix. We have found we can successfully model the strength with knowledge of the fiber length distribution the average through-thickness fiber orientation and the stress / strain curve for the unfilled resin. Surprisingly accurate strength predictions (within 10%) have been validated for both flow and cross-flow directions which can greatly simplify analysis and allows for a quick estimate of the strength values of any reinforced plastic using material data that is generally available.
DuPont™ SHIELD Technology allows polyamide and polyphthalamide resins to be used at higher temperatures than could be previously achieved. This SHIELD Technology combines several innovations including a new polymer backbone polymer modifications and a special set of additives to enhance performance. The resistance to thermo-oxidative damage and chemical degradation is highly superior to standard polyamide polyamide and polyphthalamide resins. Examples of improved performance include: Improved air oven aging-retaining >50% of initial mechanical properties after at least 1000 hours at 210°C Improved fluid aging resistance-maintaining >75% of its impact strength after 5000 hrs at 150°C in hot oil. Improved CaCl2 resistance resisting cracks three times the number of cycles of standard glass-reinforced nylons.
Automotive sunroof systems which have become a must-have for the added comfort and styling to today's cars increasingly rely on engingeering plastics functionalities to replace mtals. Structural and semi-structural sunroof module components sunroof frames in particular typically need to meet a wide range of technical requirements with a clear focus on the integration of functions safety cost and weight reduction. The glass-reinforced materials thermoplastics and thermosets currently used for sunroof frames are mostly based on PBT/ASA PBT PA PP and unsaturated polyester SMC. These products are not a perfect match for the application needs of today and the future. Glass-reinforced SMA/ABS on the other hand offers an ideal unique combination of properties required in sunroof frames and systems. SMA/ABS-GF compounds such as Polyscope's Xiran SG grades have clear technical and commercial benefits such as; high dimensional stability and precision very large warpage compliance to mold cavity shape good performance at low wall thickness high creep resistance excellent adhesion without surface treatment low density high economic value good chemical resistance and easy recylability with efficient waste streams.
To date the only types of fibre-reinforced PVC composites were made of short fibres mixed with PVC dry blend before being extruded but that process cuts the fibres giving limited properties to the finished products. New technologies have been developed that allow long and continuous fibre lengths to be maintained in PVC composites via processes without shearing. The first technology consists of a rigid impregnation of the fibres by a water-based PVC dispersion followed by drying gelation by hot air and calendering. Reinforcement can be unidirectional (UD) fibres (e.g. fiberglass) to produce tapes or in the form of fabrics to produce prepregs especially in flax fibres. The second technology consists of a dispersion of PVC powder into a network of fibres by an alternative electrostatic field followed by a gelation in a flat calender. The plates obtained present isotropic properties and an excellent ratio of rigidity to impact toughness. The presentation shows the outstanding properties obtained with these composites by keeping the original length of the fibres and the possibilities offered in term of applications.
The primary objective of the Composites Design and Manufacturing HUB (cdmHUB) is to accelerate the development of a comprehensive simulation tool set for the composites community for use in lightweighting vehicles. The cdmHUB provides a platform for the birth development refinement integration and commercialization of the simulation tools necessary to bring composites design and manufacturing simulation to a level consistent with high- performance composites simulation tools for geometric and structural modeling such as CATIA NASTRAN ABACUS and ANSYS. The cdmHUB is a cloud-based cooperative platform that can host composites design and manufacturing simulation tools that may be accessed with a web browser from the Internet.
Long fibre thermoplastics (LFT) based on polypropylene / glass fibre (PP/GF) composites has become one of the most widely used plastics in semi-structural and structural automotive applications in both aesthetic and non-aesthetic parts. LFTs are commercially available in pre-compounded pellets for injection moulding and are developed with specific properties for targeted functions. In a rationalizing effort to reduce costs heat histories and create in-house flexibility of material blending in-line compounding (ILC) of base materials including resin additives (heat stabilizers colors coupling agents etc.) and glass roving reinforcements for direct moulding of LFT parts (D-LFT) has been developed in the last 10 years. Two major versions of D-LFT technology currently exist on the market both relying on twin-screw extrusion for ILC -- one utilizing compression moulding and the other injection moulding. These two technologies have their specific features related to fibre length orientation and resulting properties. The objective of this paper is to address some of them.
The automotive industry is changing. Today less means more as engineers are challenged to reduce vehicle weight to meet CAFE and emissions regulations. This presentation will highlight several high-performance solutions for mass-reducing thermoplastic compounds / composites including the strength-to-weight advantages and design considerations for: increasing performance with glass fiber reinforcement; “stiff and tough” very-long-fiber composites; going lighter by using carbon fiber compounds including carbon fiber polypropylene; and shedding weight with glass microspheres and blowing agents.
The higher mechanical characteristics and mass specific energy absorption capabilities of composite materials motivate their use in large primary structures as well as structural and crashworthy components over more traditional metallic designs. Numerical simulation has become a common tool in structural design and crashworthiness. A well-established simulation practice is needed to significantly reduce the amount of experimental testing required during product development and certification. Due to the complex mechanical behavior of advanced composite materials the capability of the existing analytical and numerical models to predict the crushing behavior is limited. The merits and weaknesses of a progressive failure material model MAT54 of a commercially available explicit finite element solver LS-DYNA are highlighted through single-element investigations. Then the suitability of MAT54 to simulate the quasi-static crushing of a composite specimen is evaluated. Through extensive calibration by trial and error the crushing behavior of a semi-circular sinusoid specimen comprised of carbon fiber/ epoxy unidirectional prepreg tape is properly simulated both in terms of the specific energy absorption and load –penetration behavior. The study is extended to five different geometries in order to evaluate the effect of geometric features on crush behavior both from an experimental and numerical standpoint. Finally an energy-absorbing composite sandwich structural concept comprised of a deep honeycomb core with carbon fiber/ epoxy facesheets subject to through-thickness crushing and penetration is considered. With the aid of the building block approach and extensive calibration of the material models and contact formulations the full-scale crush behavior is predicted.
Modeling the behavior and failure of composite materials is challenging and requires models that take into account the material anisotropy nonlinearities and progressive damage and failure. This behavior depends on the local material composition (matrix and fibers) and underlying microstructure (fiber length content orientation) as induced by the manufacturing process. This tutorial will address the modeling of short-fiber-reinforced plastics (in Part 1) and continuous-fiber composites (in Part 2) materials and structures. Part 1 also will cover tests needed to calibrate the material model that can be used in FEA analysis taking into account the fiber orientation predicted by injection molding simulation; Part 2 also will cover the use the classical laminate theory to model the linear behavior of CFRP structures and the use of coupon test results to calibrate the nonlinear stress-strain and failure behavior of the composite.
This paper presents simulation results for prediction of fiber orientation in a center-gated disk using Folgar Tucker model with Newtonian flow and experimentally measured orientation at the gate as an initial condition. A steady moving front with circular shape was included to capture the effects of the frontal flow on fiber orientation. Quadratic and invariant-based optimal fitting closures are also assessed in shear and planar extensional flows and compared with experimental evolution of fiber orientation.
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 CAE model predictions and to better understand the effect of material and manufacturing variability prototype molded underbody components were fabricated and subsequently built into underbody assemblies to assess their structural performance. Non-destructive component and assembly tests were devised to assess the general static and modal performance of the underbody component and a quasi-static destructive test of a built-up underbody assembly was developed to simulate the deformation and loading observed in the worst case vehicle impact design load case. The paper will discuss the preparation and fabrication of the built-up test assemblies the structural stiffness and modal performance testing of trimmed underbody molded components and assemblies and the destructive testing of assemblies. The predicted performance was investigated for two composite thickness assumptions to account for the additional thickness observed in the prototype components. Predictions were then compared to the measured test results to understand the status of correlation between the response of idealized components and the as-molded prototype test components. A comparison of the non-destructive stiffness and modal test results to the predictions indicated that the stiffness and modal response were reasonable. The destructive underbody test was developed to better represent the physical composite and metallic components. The destructive underbody test was limited by buckling of the longitudinal rail. The results correlated well with predictions up until rail buckling occurred after which significant local damage was
Folgar Tucker model has been in use in commercial software for predicting fiber orientation for fiber/polymer suspensions. One of the major challenges in modeling injection molding processes is the complex flow in the frontal region. However the standard method of using the model with Hele Shaw approximation limits its capability as a prediction tool especially near the advancing front region and in the outer layers of the molded part. In this work the effects of the fountain flow region were assessed by including a simplified semi-circular cap to the finite element mesh. Simulations were performed with a fixed mesh and a full 2-D velocity field was solved using Navier Stokes equation for steady state and the orientation equations were decoupled from momentum equations. We looked at combinations of inlet conditions for orientation and the model parameters to determine which are most compatible with the geometrical simplification used to describe the front. All combinations of model parameters and initial conditions considered in this work qualitatively reproduce the measured orientation profile. However large discrepancies between predicted and experimental orientation near the walls suggest the need for a robust approach to handle the effects of the advancing front on fiber orientation.
The Automotive Composites Consortium (ACC) is conducting a multi-year project to develop a better understanding of the root causes of the visual surface distortion effect known as bond-line read-through (BLRT). Initial studies using a finite-element analysis (FEA) based approach showed good agreement with experimental observations and highlighted the importance of accounting for viscoelastic adhesive material properties. A parametric FEA-based study of a small laboratory scale coupon was conducted to examine the effect of the adhesive joint cross-section geometry and adhesive type on the predicted peak curvature resulting from an elevated temperature adhesive cure. The parameters evaluated in this study were uniform and non-uniform adhesive thickness SMC substrate thickness adhesive bead width and adhesive type.
Hydrogen fuel cell-driven electric cars continue on a slow but steady progression toward commercial viability. Dismissed by many as being too expensive fuel cells are within range of the cost of other vehicle propulsion systems due to advancements in design and manufacturing that have taken place in recent years. Composites have been an integral part of the success of proton exchange membrane (PEM) fuel cells. Bipolar plates made from conductive bulk molding compound have proven to be effective durable and low cost in comparison to other materials. This presentation documents properties recent developments and successful commercialization of thermoset bulk molding compound for transportation fuel cell applications.
Automakers have developed successful computer simulation processes to meet the most stringent crash noise/vibration/ harshness (NVH) and aerodynamic and vehicle dynamics requirements making computer-aided engineering (CAE) an established component in today vehicle-design process. Engineers and management are comfortable with CAE deliverables for traditional metal-based vehicle design and now require reliable simulation technologies and methods to integrate engineered plastic such as carbon fiber laminates in their standardized and automated simulation procedures. This presentation will discuss the challenges of composite material calibration how CAE simulation can be used to aid material characterization the unique modeling and visualization requirement for composites and how optimization simplifies the design of laminate composite structures tailoring the material itself to the loading requirements and avoiding overdesign of part.
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