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Morphological features of voids were characterized for T300/924 12-ply and 16-ply composite laminates at different porosity levels through the implementation of a digital microscopy (DM) image analysis technique. The composite laminates were fabricated through compression molding. Compression pressures of 0.1MPa, 0.3MPa, and 0.5MPa were selected to obtain composite plaques at different porosity levels. Tension-tension fatigue tests at load ratio R=0.1 for composite laminates at different void levels were conducted, and the dynamic stiffness degradation during the tests was monitored. Fatigue mechanisms were then discussed based on scanning electron microscope (SEM) images of the fatigue fracture surfaces. The test results showed that the presence of voids in the matrix has detrimental effects on the fatigue resistance of the material, depending on the applied load level.

The introduction of carbon fiber reinforced polymer (CFRP) composites to structural components in lightweight automotive structures necessitates an assessment to evaluate that their crashworthiness dynamic response provides similar or higher levels of safety compared to conventional metallic structures. In order to develop, integrate and implement predictive computational models for CFRP composites that link the materials design, molding process and final performance requirements to enable optimal design and manufacturing vehicle systems for this study, the dynamic mechanical response of unidirectional (UD) and 2x2 twill weave CRFP composites was characterized at deformation rates applicable to crashworthiness performance. Non-standardized specimen geometries were tested on a standard uniaxial frame and an intermediate-to-high speed dynamic testing frame, equipped with high speed cameras for 3D digital image correlation (DIC).

Woven fabric carbon fiber/epoxy composites made through compression molding are one of the promising choices of material for the vehicle light-weighting strategy. Previous studies have shown that the processing conditions can have substantial influence on the performance of this type of the material. Therefore the optimization of the compression molding process is of great importance to the manufacturing practice. An efficient way to achieve the optimized design of this process would be through conducting finite element (FE) simulations of compression molding for woven fabric carbon fiber/epoxy composites. However, performing such simulation remains a challenging task for FE as multiple types of physics are involved during the compression molding process, including the epoxy resin curing and the complex mechanical behavior of woven fabric structure.

Adoption of high-pressure common-rail (HPCR) fuel systems, which subject diesel fuels to higher temperatures and pressures, has brought into question the veracity of ASTM International specifications for biodiesel and biodiesel blend oxidation stability, as well as the lack of any stability parameter for diesel fuel. A controlled experiment was developed to investigate the impact of a light-duty diesel HPCR fuel system on the stability of 20% biodiesel (B20) blends under conditions of intermittent use and long-term storage in a relatively hot and dry climate. B20 samples with Rancimat induction periods (IPs) near the current 6.0-hour minimum specification (6.5 hr) and roughly double the ASTM specification (13.5 hr) were prepared from a conventional diesel and a highly unsaturated biodiesel. Four 2011 model year Volkswagen Passats equipped with HPCR fuel injection systems were utilized: one on B0, two on B20-6.5 hr, and one on B20-13.5 hr.

Polymers are one of the major constituents in electrical components. A study investigating pre-combustion off-gassing and particle release by polymeric materials over a range of temperatures can provide an understanding of thermal degradation prior to failure which may result in a fire hazard. In this work, we report simultaneous measurements of pre-combustion vapor and particle release by heated polymeric materials. The polymer materials considered for the current study are silicone and Kapton. The polymer samples were heated over the range 20 to 400°C. Response to vapor releases were recorded using the JPL Electronic Nose (ENose) and Industrial Scientific's ITX gas monitor configured to detect hydrogen chloride (HCl), carbon monoxide (CO) and hydrogen cyanide (HCN). Particle release was monitored using a TSI P-TRAK particle counter.

Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). In this paper, two different injection molding tests were completed. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line region. Tensile samples were cut at different locations along the weld line on the injection molded plaques. The test results showed that both UTS and fracture strain increase when the sample locations are away from the insert. This trend is attributed to different meeting angles. Second, standard ISO tensile bars with and without weld line were injection molded to identify the size of the weld line affected zone. A FEA model was built in ABAQUS, where the tensile sample was divided into two different regions, the solid region and the weld line affected region.

The lack of electrical conductivity on materials, which are used in automotive fuel systems, can lead to electrostatic charges buildup in the components of such systems. This accumulation of energy can reach levels that exceed their capacity to withstand voltage surges, which considerably increases the risk of electrical discharges or sparks. Another important factor to consider is the conductivity of the commercially available fuels, such as biodiesel, which contributes to dissipate these charges to a proper grounding point in automobiles. From 2013, the diesel regulation in Brazil have changed and the levels of sulfur in the composition of diesel were reduced considerably, changing its natural characteristic of promoting electrostatic discharges, becoming more insulating.

Recently, graphene has attracted both academic and industrial interest because it can produce a dramatic improvement in properties at very low filler content. This review will focus on the latest studies and recent progress in the swelling resistance of rubber compounds due to the addition of graphene and its derivatives. This work will present the state-of-the-art in this subject area and will highlight the advantages and current limitations of the use of graphene for potential future researches.

High mileage NVH performance is one of the major concerns in vehicle design for long term customer satisfaction. Elastomeric bushings and brake rotors are key chassis components which tend to degrade as vehicle mileage accumulates with time. The degradation of these components normally causes the overall degradation of vehicle NVH performance. In the current paper two categories of problems are addressed respectively: road-induced vibration due to bushing degradation, and brake roughness due to rotor wear. A system integration approach is used to derive the design strategies that can potentially make the vehicle more robust in these two NVH attributes. The approach links together bushing degradation characteristics, brake rotor wear characteristics, the design of experiment (DOE) method, and CAE modeling in a systematic fashion. The concept and method are demonstrated using a production vehicle.

This paper describes the process of incorporation of 25% post-industrial recycled sheet molded composite (SMC) material in the 1998 Continental Hood inner. 1998 Continental Hood assembly consists of traditional SMC outer and this recycled hood inner along with three small steel reinforcements. BUDD Plastics collects SMC scraps from their manufacturing plants. The scrap is then processed and made into fillers for production of SMC. Strength of SMC comes from glass fibers and fillers are added to produce the final mix of raw materials. This recycled material is approximately 10% lighter and less stiff than the conventional virgin SMC. This presented unique challenges to the product development team to incorporate this material into a production vehicle in order to obtain the desired goal of reducing land fill and improving the environment.

This paper describes the results of permeation and sorption tests conducted to assess the properties of several plastic materials as barriers to fuel. The materials examined include ethylene-vinyl alcohol copolymers (EVOH), nylon, high density polyethylene, polyketone, poly-vinyledene fluoride (PVDF) as well as tetra-fluoro-ethylene, hexa-fluoro-propylene and vinyledene fluoride terpolymers (THV). The permeation from thin films of these materials exposed to methanol or CM15 was analyzed (speciated) by gas chromatography. These results are compared to those of parallel sorption experiments conducted on the same materials. The goal of this work is to determine the materials best suited for fuel barrier applications.

FMVSS 207/210 relates to seat system forward longitudinal strength and is one of the most important safety requirements for seats. Seat performance to satisfy FMVSS 207/210 can be simulated using LS-DYNA FEA code. When developing a seat design there is often a need to optimize the design to satisfy requirements/meet targets and to minimize weight. However LS-DYNA does not have optimization capabilities. This paper shows how the response surface based optimization can be used to meet FMVSS 207/210 requirements and reduce weight. A number of DOE runs are performed with different combinations of upper/lower/baseline gages. Data are collected for the maximum Von Misses stress and maximum effective plastic strain in each of the major seat parts along with the total weight of the seat. Based on the collected data the response surfaces are generated using Gaussian Stochastic Kriging method.

Compressible plastic foams are used throughout the interior and bumper systems of modern automobiles for safety enhancement and damage prevention. Consequently, modeling of foams has become very important for automobile engineers. To date, most work has focused on predicting foam performance up to approximately 80% compression. However, in certain cases, it is important to predict the foam under maximum compression, or ‘bottoming-out.’ This paper uses one such case-a thin low-density bumper foam impacted by a pedestrian leg-form at 11.1 m/s-to investigate the ‘bottoming-out’ phenomenon. Multiple material models in three different explicit Finite Element Method (FEM) packages (RADIOSS, FCRASH, and LS-DYNA) were used to predict the performance. The finite element models consisted of a foam covered leg-form impacting a fixed bumper beam with a foam energy absorber.

We have characterized the mechanical behavior of three commercially available polycarbonate-polybutylene terephthalate (PC-PBT) blends with and without thermoplastic film during quasi-static (1.7 × 10-5 m/s) and dynamic (2.2 and 8.9 m/s) three-point bend loading at -30, 22, and 88 °C. The materials tested were not very sensitive to testing speed. Flexural moduli decreased 20 to 30 % with increasing impact speed for one of the blends and remained constant for the other two materials; flexural strength increased 25 to 30 % with test speed. The presence of film did not have a statistically significant effect on strength, stiffness, or energy absorption in most cases. Testing temperature was found to have the most significant effect. Flexural stiffness, flexural strength and energy absorption during 2.2 m/s impacts increased 10 to 20 % at -30 °C and decreased 30 to 40 % at 88 °C.

Effects of impact velocity on the crush behavior of aluminum 5052-H38 honeycomb specimens are investigated by experiments. An impact test machine using pressurized nitrogen was designed to perform dynamic crush tests. A test fixture was designed such that inclined loads can be applied to honeycomb specimens in dynamic crush tests. The results of dynamic crush tests indicate that the effects of impact velocity on the normal and inclined crush strengths are significant. The trends of the inclined crush strengths for specimens with different in-plane orientation angles as functions of impact velocity are very similar to that of the normal crush strength. Experimental results show similar progressive folding mechanisms for honeycomb specimens under pure compressive and inclined loads. Under inclined loads, the inclined stacking patterns were observed. The inclined stacking patterns are due to the asymmetric locations of the horizontal plastic hinge lines.

There are many different vibration sources in a car. Engine, gears, road roughness, impacts against the wheels cause vibration and sound that can decrease the parts and the car durability as well as affect drivability, safety and passengers and community comfort. In 4×4 cars, some extra vibration sources are the parts responsible for transmitting the torque and power to the rear wheels. Each of them has their own vibration modes, excited mostly by its imbalance or by the second order engine vibration. The engine vibration is a very well known phenomena and the rear driveshaft is designed not to have any vibration mode in the range of frequencies that the engine works or its second order. The imbalance of a driveshaft is also a design requirement. That means, the acceptable imbalance of the driveshaft is limited to a maximum value.

Experimental modal analysis (EMA) provides many parameters that are required in numerical modeling of dynamic and vibratory behavior of structures. This paper discusses EMA on an exhaust system of an off-road car. The exhaust structure is tested under three boundary conditions: free-free, supported with two elastomeric mounts, and mounted to the car. The free-free modal parameters are compared to finite element results. The two-mount tests are done with the mounts fixed to a rigid and heavy frame. The rigidity of the frame is verified experimentally. The on-car test is done with realistic boundary conditions, where the exhaust structure is fixed to the engine manifold as well as the two elastomeric mounts. The two-mount and the on-car tests result in highly complex mode shapes.

A methodology for modeling elastomeric mounts as nonlinear lumped parameter models is discussed. A key feature of this methodology is that it integrates dynamic test results under different conditions into the model. The first step is to model the mount as a linear model that is simple but reproduces accurately results from dynamic tests under small excitations. Frequency Response Functions (FRF) enables systematic calculation of the parameters for the model. Under more realistic excitation, the mount exhibits non-linearity, which is investigated in the next step. For nonlinear structures, a simple and intuitive method is to use time-domain force-displacement (F-x) curves. Experiments to obtain the F-x curves involve controlling the displacement excitation and measuring the induced forces. From the F-x curves, stiffness and damping parameters are obtained with an optimization technique.

This paper presents the continuation of the modeling work described in a companion paper “Modeling of Nonlinear Elastomeric Mounts. Part 1: Dynamic Testing and Parameter Identification” by the same authors. That paper discussed a dynamic test procedure and an optimization methodology to identify and model an elastomeric mount as a non-linear lumped parameter structure. This paper discusses a numerical modeling methodology to confirm or improve the agreement between the dynamic test results and the input-output relationship of the analytical model generated in the companion paper. In this paper, the model developed in the companion paper and the model parameters are input into a dynamic simulation model using a commercial simulation package. The model is then run to produce the numerical force-versus-displacement (F-x) curves of the mount. The numerical F-x curves are compared with the F-x curves obtained from the experiments.

The sound barrier performance of elastomeric vehicle weather seals was investigated. Experiments were performed for one bulb seal specimen following a reverberation room method. The seal wall vibration was measured using a laser Doppler vibrometer. The acoustic pressure near the seal surface was measured simultaneously, allowing the sound intensities on both side of the seal, and the sound transmission loss to be evaluated. The vibration response of the bulb seal and its sound transmission loss were then computed using the finite element method. Model predictions for the same seal geometry were found to be in excellent agreement with the experimental data within the frequency range of interest, comprised between 500 Hz and 4000 Hz.