Fatigue Behavior of Neat and Short Glass Fiber Reinforced Polymers under Two-Step Loadings and Periodic Overloads
Abstract An experimental study was conducted to evaluate the variable amplitude fatigue behavior of a neat polymer (polypropylene impact co-polymer) and a polymer composite made of polybutylene terephthalate (PBT) with 30 wt% short glass fibers. Fatigue tests were conducted on un-notched and notched specimens at room temperatures. Plate-type specimens were prepared in the transverse direction with respect to the injection mold flow direction and a circular hole was drilled in the center of notched specimens. Two-step loadings (high-low and low-high) tests at two damage ratio of 0.2 and 0.5 at stress ratios of R = 0.1 and -1 were conducted to investigate load sequence effects and prediction accuracy of the linear damage rule. Different behaviors were observed for unreinforced and short glass fiber reinforced polymers under the two-step loading tests.
Abstract Short glass fiber reinforced polyamides (SFRPs) are a choice material for automotive industry, especially for in the engine compartment. To develop their application field to more and more complex hydrothermal and mechanical environments, reliable or even predictive simulation technologies are necessary. Integrative simulation takes into account the forming process during final Finite Elements Analysis (FEA). For SFRPs, injection molding is taken into account by computing glass fibers orientation. It is further used to compute a specific anisotropic constitutive model on each integration point of FEA model. A wide variety of models is now available. Integrative simulation using Digimat has been proved very efficient for static and dynamic loadings.
Effect of Water Absorption on Tensile and Fatigue Behaviors of Two Short Glass Fiber Reinforced Thermoplastics
Abstract An experimental study was conducted to evaluate the effect of water absorption on tensile and fatigue behaviors of an impact-modified short glass fiber polyamide-6 and a short glass fiber polybutylene terephthalate. Specimens were prepared in the longitudinal and transverse directions with respect to the injection mold flow direction and immersed in water. Kinetics of water absorption was studied and found to follow the Fick's law. Tensile tests were performed at room temperature with specimens in the longitudinal and transverse directions and with various degrees of water absorption. Mathematical relations were developed to represent tensile properties as a function of water content. Load-controlled tension-tension fatigue tests were conducted in both longitudinal and transverse directions and correlations between tensile and fatigue strengths were obtained.
Effect of Fiber Orientation on the Mechanical Properties of Long Glass Fiber Reinforced (LGFR) Composites
Abstract Long glass fiber reinforced (LGFR) composites have been widely used in automotive industry to reduce vehicle weight and maintain relatively high mechanical performances. Due to the injection molding process, the distribution of fiber orientations varies at different locations and through the panel thickness, resulting in anisotropic and non-uniform mechanical properties. The current practice of computer modeling of these materials is generally using isotropic properties adjusted by a certain scale factor. The effect of fiber orientation is not carefully considered due to the complexity of fiber orientation distribution in the LGFR parts. The purpose of this paper is to identify key factors affecting vehicle attribute performances where LGFR composites are used; and provide an efficient way for accurate CAE modeling of LGFR composites. In this study, tensile coupons cut from a simple geometric injection molded plaque are tested.
The definition method and the two load/source method of a transmission loss test of an automotive tuning device are discussed in this paper. For the definition method, the accuracy penalty due to the imperfect anechoic termination quality is studied based on an empirical acoustic model of glass-wool and the best practice of constructing an anechoic termination is attempted. The conclusion is verified with numerical simulations. For the two load/source method, the difference in the two source/load impedances compounded with the error of measured acoustic pressures, as related to transmission loss accuracy, is discussed and demonstrated.
Composite materials have found applications in the aviation industry because of an appropriate combination of properties - high stiffness, high heat performance and lower specific gravities. The Automotive industry has similar needs, and the application of composites in semi-structural application is a natural next phase. This is also necessitated because of global emphases on fuel efficiency and safety considerations in automotive applications. In this paper, thermoplastic composite material technology solutions and case studies for a number of applications, such as front-end-modules, door modules and instrument panel carriers are presented. Since processing and material modeling of composites is of critical importance in the design process, this paper also describes a new definition of isotropic properties of long glass composites, and perhaps the only way of honestly comparing such materials.
Shrinkage Analysis of a Constrained Thin Walled Injection Molded Component Using a Traditional Flatbed Scanner and Photometric Techniques
A study was performed to determine the effects of varying the wall thickness and material glass fiber concentration for parallel and perpendicular shrinkage rates for a constrained thin-walled box shaped component. An analysis of the shrinkage for the bottom portion of a 3 dimensional constrained thin walled injection molded component was performed using measurements made from bitmap images of the components that were obtained from a traditional flatbed scanner. The shrinkage rates were determined by comparing mold cavity hatch lines to the correlating transposed hatch lines on the plastic molded component. The perpendicular and parallel shrinkage rates were determined and are discussed as a function of thickness and glass fiber content. A wide range of processing control factors was used in the study.
This work presente a type of composite material that can be used in the manufacture or repair of ducts in draining of petroleum and derivatives. The characterization of microstructures, identification of the type of matrix and volumetric fraction of the composite material are presented. The composite material was submitted the aging in petroleum for a maximum period of 30 days in the temperature of 60°C and atmospheric pressure. The microstructural characterization was effected before and after the procedure of aging in petroleum. The composite material used has polyester matrix and continuous fiberglass and lined. The microstructure after the aging indicated the absorption of petroleum for the composite material, mainly for infiltration through the surface and porosities and for the interface between fiber and matrix. Also, curve of absorption of petroleum in function of the time is presented.
A polymer electrolyte membrane (PEM) fuel cell powered uninhabited air vehicle using compressed hydrogen, is being developed by California State University, Los Angeles in collaboration with Oklahoma State University and Horizon Fuel Cell Technologies. A 150-Watt PEM fuel cell, augmented by a 60 Watt, 350-mAH lithium ion battery pack, powers an aerodynamically efficient composite airframe constructed of carbon and fiberglass. The battery provides additional power for takeoff and climb while the fuel cell powers cruise conditions. The UAV has an overall weight of 5 kg and a 4-meter wingspan. A test flight is scheduled for September, 2007 with the goal of achieving a world record flight time of 16 hours for this class of UAV.
Fiberglass laminated parts are used in automotive industry, especially for limited quantities of parts production. They are useful on prototypes and special vehicles, among other things. If the parts are not laminated with required quality, the result can jeopardize the vehicle parts application. This paper shows a simple manner of vacuum bagging process application for fiberglass and carbon fiber parts lamination with dimensional and surface quality required. It also shows the mould fabrication process and its importance to the laminated parts quality.
Research Work for the Improvement of the Durability of Glass Fiber-Reinforced Nylon 66 by Modifying the Glass Fiber Diameter
As for the polyamide (nylon) resins, i.e., nylon 6, nylon 66, nylon 46 and so on, when they are reinforced by glass fibers (GF), their static mechanical strength and heat distortion temperature increase considerably, and many faults of them are improved. However, when repeating stress is applied to a GF-reinforced nylon, the interface stress concentration between nylon and GF is easily to happen and so, depending upon working condition, the damage phenomenon similar to fatigue flaking is often observed for the GF-reinforced nylon by the reason of the insufficiency of interface strength between nylon and GF. In this study, thus, it mainly focused on the improvement of the fatigue property of GF-reinforced nylon. Actually, we compounded of nylon 66 and GF the fiber diameter of which was smaller than conventional GF, and investigated the mechanical and physical properties of the nylon 66 / GF composite we prepared.
A Math-Based Methodology for Fatigue Longevity Prediction of 3D Woven Fiberglass Reinforced Vinyl-ester Composites
In the DOE-Delphi Composite Chassis Cross-Member program, 3TEX 3Weave™ (3D woven fiberglass mat)/vinyl-ester (Dion 9800™) composites have been investigated as a candidate material. One of the most important mechanical properties for qualifying these composites for such applications is the mechanical fatigue longevity. In this work, a predictive math-based technology has been developed as a virtual engineering tool for the design of 3TEX 3Weave™/vinyl-ester composite parts by using a state-of-the-art simulator, GENOA™ (Generalized Optimization and Analysis) PFA (Progressive Failure Analysis), developed jointly by Alpha Star Corp and NASA. This math-based GENOA™ methodology effectively tracks the details of damage initiation, growth, and subsequent propagation to fracture, for composite structures subjected to cyclic fatigue, thereby predicting the fatigue life.
Material Modeling and Finite Element Analysis of Hydroform - Short Glass Fiber Filled Thermoplastic Front-End Structures
Abstract Increasing use of engineering thermoplastics in the applications such as load bearing automotive components necessitates accurate characterization and material modeling for predicting part performance using finite-element simulations. Uniaxial tensile test data on glass filled thermoplastic resins exhibit highly nonlinear deformation with no clear demarcation between elastic and plastic regions. Hence, the estimation of modulus and yield stress values, required for the finite element analysis, is invariably through the subjective interpretation of the CAE analyst, which may not be consistent and unique. Use of parameters such as tangent modulus, yield stress and the post yield data calculated at 0.2% strain for finite element computations does not yield good correlations with experimental values. This paper outlines an alternate approach for evaluating material parameters for short glass filled engineering thermoplastics.
Transmissibility and Experimental Analyses of Laminated Fibrous Micro-Composite E-Springs for Vehicle Suspension Systems
E-spring is an optimized trend of springs for vehicle suspension systems. Experimental and transmissibility analyses of laminated fibrous composite E-springs are conducted. The mechanical and frequency-response-based properties of these springs are investigated experimentally at both of the structural and constitutional levels. Thermoplastic-based and thermoset-based fibrous composite structures of the E-springs are modified at micro-scale with various additives and consequently they are compared. The experimental results reveal that additives of micrometer-sized particles of E-glass fibers as well as mineral clay to an ISO-phthalic polyester resin of the composite E-spring can demonstrate superior characteristics. The transmissibility analysis of laminated fibrous composite E-springs reveals superior frequency ratio.
The advantage of higher strength to weight and higher stiffness to weight ratios for composite structure compared to metallic structure is well known in the aerospace industry, especially to commercial airline world. Its increased usage in the airplane structure is a direct reflection of the benefit in reduction of operating costs by lowering the fuel usage. This factor turned out to be more important for the airlines after the September 11, 2001 incident and also due to the increase in fuel prices. Besides reduction in the operating costs, airlines are seeking ways to reduce their maintenance costs. Most of the damage to the aluminum structure airplanes is attributed to corrosion. The non-metallic composite structure has an excellent property of resistance to corrosion. The structure is more damage tolerant due to the absence of fastener holes. As a result, its increased usage serves the airlines by lowering the maintenance and inspection costs.
The damage generated during the drilling of Glass Fiber Reinforced Plastics (GFRP) is detrimental for the mechanical behavior of the composite structure. Effect of drill geometry on drilling of glass/epoxy (GFRP) laminates using three types of drill, namely standard twist drill, Zhirov point and multifacet (MFD) has been studied. A woven glass fiber reinforced plastic laminate of 9 mm thickness was prepared and drilling was carried out using a CNC vertical machining centre. The thrust force and hole quality machined during drilling were compared for each drill geometry. Zhirov drill gives the benefit of less cutting force, and best surface finish. From the experiments it is found that the multifacet drill produces delamination free hole and better surface finish among other two geometries.
An aircraft rotatable airfoil assembly in the nature of a helicopter machine and having two airfoils diametrically disposed about an axis of rotation. Air baffles are mounted on the radially inner and radially outer ends of the airfoils and for blocking the vortices inherently generated by the orbiting of the airfoils. The baffles thereby avoid vortices which reduce the lift force on the aircraft by eliminating the air flow from under the airfoil to above the airfoil and around the airfoil inner and outer ends. The assembly can be included in an airliner or an automobile. The aircraft is arranged for vertical and horizontal flight.
Expandable reinforcing material such as that used for the outer panel of a door has been used to compensate for the lack of stiffness in automotive body panels. This material can improve panel stiffness and reduce vibration that causes radiated noise. Material properties in practical use have generally been evaluated by sensory methods. These properties, however, have not been sufficiently quantified to optimally design reinforcing material. We have developed evaluation methods aimed at ensuring reinforcement and also at reducing vibration and deformation in a panel. By employing these evaluation methods along with simulation of a material's basic properties, we are able to achieve the optimal design of materials for outer body panels.
This paper describes the design and development of the rear compartment structure of the sixth generation Corvette, C6, which starts in the 2005 model year. The improved design integrates the rear compartment packaging to address issues seen on fifth generation Corvette, C5. The molded composite fiberglass reinforced, tub and surround panels are similar to the C5. These large panels are modified to fit the new styling theme of the C6, while also addressing the packaging requirements of the updated underbody structure and exhaust system. New composite side support brackets and cross car reinforcement combine to address several desired improvements. These side support brackets are designed to package the rear audio speakers, electrical modules, wiring and cable routing while also addressing build variation and localized stiffness improvement. The side brackets support the surround panel increasing the manufacturing control of the surround panel.
The use of injection molded long glass fiber composites to replace metal in automotive components continues to find success. This paper will discuss the use of these composites to replace steel in running boards, a very demanding application. The success of an injection molded-in-color composite running board on a 2004 mid size SUV has opened the door to realize the benefits of composites in these large exterior parts. These benefits include significant weight reduction, corrosion resistance, scratch and mar resistance, design flexibility, and cost out opportunities. 40% long glass fiber polypropylene was formulated to meet the rigorous structural and aesthetic requirements demanded by global OEM manufacturers for these large structural parts.
Investigation and Analysis of the Influences of Glass Fiber Content and Orientation on the Dimension Change of Reinforced Polyamide Parts due to Moisture Absorption
The investigations in this work were focused on the determination and analysis of the factors such as contents and orientations of glass fibre, which influence the dimension change of reinforced polyamide parts significantly. The influence of various environmental conditions on dimensional changes of reinforced polyamide parts was also investigated and a correlation between the dimension change, glass fiber content and orientation under various conditions has been established. On the basis of process parameters in the injection molding of the tested standard specimens and technical parts, the glass fibre orientations in the part were simulated with help of the software tool MoldFlow. In correlation with the determined expansion coefficients of standard specimens, the expansion of further standard specimens and of technical parts was calculated by the help of Finite Element Analysis. The calculated results for the polyamide parts were compared with the measured values.
The Ford GT is a niche vehicle with a very limited production volume. A solution was needed that would minimize cost, particularly up-front investment, and produce a lightweight, high-class vehicle interior, while maintaining the standard quality, material and design requirements.
Dent resistance has become one of the key performance criteria of automotive outer body panels due to the increased use of lightweight sheet steels for vehicle weight reduction. In order to sustain or improve the dent resistance of body panels with reduced metal thickness, commercial patches have been attached to the inner surface of exposed panels. The actual patch effects on dent resistance are not evident. Hence, the understanding of benefits of using a patch to improve dent resistance is also limited. In this study, the effects of a patch on dent resistance are investigated. A special fiberglass patch is developed to compare with commercial patches. Fixed load  and fixed speed, single loading conditions are carefully designed and incorporated into the quasi-static and dynamic dent test. For comparison purposes, the incremental quasi-static loading condition is also examined.
Eco-efficient and cost effective natural fibre - thermoplastic composites have gained attention to a great extent in the automotive industry. Most of the OEM specifications for automotive interior parts, for example, instrument panels, recommend the composite should have a minimum flexural modulus of 1900 MPa, a notched Impact strength greater than 150 J/m at room temperature and a melt flow index of 5 g/10min and above [1, 2 and 3]. The objective of this work was to develop a high performance hybrid composite by injection molding process of the composites made from natural fibre in combination with glass fibre or calcium carbonate in a thermoplastic matrix to meet the specifications required for automotive interior parts applications. Mechanical properties, such as tensile and flexural strengths and moduli of the composites prepared, were found to be highly promising.
The advantages of magnetic implant induction welding (Emabond™)1 technology for various thermoplastics were widely discussed since the mid-eighties in a series of technical articles and reports, and presented to the professional Societies (SAE, SPE, SME, etc). In 1998-2003, we reported to SAE International our technical achievements in optimizing the mechanical performance of welded nylon (6, 66, 6/66, 46, etc.) using frictional (linear and orbital vibration, ultrasonic), contact (hot plate), and non-contact (laser through-transmission) welding technologies. Our recent developments focused on optimization of mechanical performance of induction welded nylon 6, which has reached a new performance level through continuous improvement of magnetic implant induction welding technology, including properties of the formulated magnetic implant material, new equipment, SPC process control, optimized design of joints, etc.
Investigation and Description of the Weight and Dimension Change of Injection Molded Polyamide Parts by Moisture Absorption
In the scope of this work, the weight and dimensional changes of norm test pieces and technical parts (e.g. cages) of reinforced and unreinforced polyamides due to moisture absorption have been investigated. The diffusion coefficients of the tested polyamides for various conditioning environments were determined on the basis of the test results. The weight change due to moisture absorption as function of conditioning time can be represented within a limited tolerance from the measured results by using the Fick's Diffusion Law and an appropriate geometric factor. Furthermore, the dimensional change in relation to weight increase of tested parts were determined and presented here. Further, the influences of fiber content and orientation on the dimension change of various reinforced test parts were investigated.
Optimization of Manufacturing Process of Glass Fibers/Phenol Composites. Effects of Solidification Conditions, Fiber Length and Additional Materials on their Mechanical Properties
The aim of these experiments is to determine the best way to obtain high mechanical properties for phenol resin and glass fibers based composites. Various ways of fabricating the material were studied, as well as its best composition. The conditions of drying, molding processes were optimized. From the most conventional method, using ethanol as a solvent to newer ones, including continuous ways of processing and the use of water instead of ethanol, a lot of possibilities exist to produce such a material. This paper explains the advantages and drawbacks of a whole range of manufacturing processes.
The use of door modules as a pre -assembled functional unit inside a car door is discussed. This includes reasons why a door module should be used and why a long glass fiber reinforced polypropylene (PP) product is a good material of choice. As an example the development of the door modules for the new Ford Fiesta is given, including the mechanical and production design of the StaMax® P long glass PP carrier. * Special attention is paid to the excellent dimensional reproducibility of this material which is critical for door module designs in which the carrier also manages the wet and dry separation (e.g. “sealed” designs). Further integration potential for future door modules is also highlighted.
The effect of laser welding parameters such as laser power, laser speed, working distance and weld pressure on the weld strength, microstructure and meltdown of modified T-joints were studied using a diode laser and a contour welding technique. Specimens made of 30% glass reinforced nylon 6 were used in this study. A regression model was fitted to the data based on a central composite experimental design. The model showed that low levels of laser power at lower laser speed gave the maximum weld strength. It was observed that increases in weld pressure had a negative effect on weld strength. Meltdown was found to increase proportionally to the line energy and weld pressure.
Modular front-end carriers to pre-assemble front-end components such as cooling systems, lights, and bumper beam have been in production in different vehicles for several years. Compression molded or overmolded steel/plastic carriers have traditionally been used. The present paper explains the design, material options, and engineering optimization of a composite front-end carrier, which utilizes long glass fiber injection moldable resins and adhesively bonded steel reinforcements. Experimental evaluation of prototypes shows the system met the functional performance requirements at minimum weight.