Browse Topic: Foams
For sustainability reasons, the automotive market is requesting 100% monomaterial noise treatments, particularly for the end-of-life recycling without any part separation operation. But also, OEMs require super light, highly performance insulating noise treatments for electric vehicles in order to extend vehicle autonomy. PP melt-blown fiber felts present good mono-material characteristics with very good absorption, but generally not so good insulation properties behind an airtight barrier due to lack of stiffness. Moreover, these PP melt-blown fiber felts are relatively expensive and not thermoformable, thus forcing them to be used as 2D die-cut parts behind existing hard or soft trims classically. The shown optimization approach proposes to return to 100% thermoformable recycled and recyclable PET formulations blending unusual coarse mechanical specific fibers, in order to optimize the viscothermal exchanges, while maintaining good mechanical properties, with microfibers for best dissipation properties bonded by bi-component fibers. The insulation properties obtained as poroelastic spring behind a barrier allow a weight reduction of -50% compared to cotton felt while being 1 dB better for the Insertion Loss values (2 dB compared to a flexible foam) and perform as well as best PP melt-blown fiber felts while being more competitive as well as thermoformable. It is possible to adjust the sound insulation properties, sound absorption and hardness (static compressibility) using optimal PET fibers formulations but also thanks to felt verticalization processes. These optimization levers will be illustrated in this paper.
This paper investigates the feasibility of using flax fiber-reinforced composites in combination with additively manufactured polymer cores for helicopter rotor blades. A new rotor blade with flax composite spar and skin laminates and a 3D-printed ASA Aero core was designed to be geometrically equivalent to an existing carbon fiber/foam reference blade of the MERIT rotor test rig and manufactured using identical tooling. Material characterization included compression testing of the printed core at ambient and elevated temperatures, single-lap shear adhesion testing with epoxy laminates, and hygroscopic conditioning of core and laminate specimens. Structural testing comprised static beam bending, experimental modal analysis with axial pre-loading to approximate centrifugal stiffening, and sustained-load creep and recovery testing of the flax blade. The results show that the 3D-printed core provides sufficient compressive stiffness at curing temperature and adhesion to epoxy laminates, enabling its use as an internal consolidation tool during blade manufacturing. Compared to the carbon reference blade, the flax/3D blade exhibits reduced flapwise and lead–lag bending stiffness, altered modal behavior, and pronounced viscoelastic effects, including creep, incomplete recovery, and strong hygroscopic swelling. Component-level hygroscopic tests reveal that moisture-induced mass and thickness changes can generate sufficient internal stresses to locally initiate structural damage. Overall, the study identifies key limitations and design considerations for applying flax fiber composites in primary rotor blade structures.
Foam material models for automotive structural analysis typically require tensile and compressive data at multiple strain rates. The testing is costly and may require a long time to complete. For many applications, foams of similar chemistry are used and the foam structural responses, such as stiffness and compression force deflection, are controlled by the foam density. In such cases, Machine Learning (ML) lends itself as an ideal tool to detect the trends in material response based on density and strain rate. In this paper, two sets of polyurethane (PU) foams of different densities were tested at four strain rates ranging from 0.01/s to 100/s. ML models capable of predicting compressive stress-strain response for a range of densities were developed. The models demonstrated good prediction capability for intermediate strain rates at all foam densities and in extrapolating stress-strain curves at higher densities at all strain rates. The strain rate trends for density outside of the training data set were also correctly predicted by the models. This demonstrated that ML tools can successfully be used to estimate material stress-strain response thus significantly reducing the testing cost and time.
A study led by Tohoku University, Iwate University, The Japan Aerospace Exploration Agency (JAXA), National Astronomical Observation of Japan, Tokyo City University, and Kyoto University developed a novel copper-based alloy that exhibits a special shape memory effect at temperatures as low as -200 °C. Shape memory alloys can be deformed into different shapes when cold, but will revert back to their original shape when heated (as if “remembering” their default state, like memory foam). This exciting new alloy has the potential to be used for space equipment and hydrogen-related technologies, where challenging, cold environments below -100 °C are the norm.
Ride comfort is an important factor in the development of vehicles. Understanding the characteristics of seat components allows more accurate analysis of ride comfort. This study focuses on urethane foam, which is commonly used in vehicle seats. Soft materials such as urethane foam have both elastic and viscous properties that vary with frequency and temperature. Dynamic viscoelastic measurements are effective for investigating the vibrational characteristics of such materials. Although there have been many studies on the viscoelastic properties of urethane foam, no prior research has focused on dynamic viscoelastic measurements during compression to simulate the condition of a person sitting on a seat. In this study, dynamic viscoelastic measurements were performed on compressed urethane foam. Moreover, measurements were conducted at low temperatures, and a master curve using the Williams–Landel–Ferry (WLF) formula (temperature–frequency conversion law) was created.
One of the five major performances of vehicles, NVH(Noise, Vibration, Harshness), has recently emerged in electric vehicles, again. And, front loading NVH simulation is essential to respond nimbly to automotive industry these days. However, the two components of the simulation, mathematical sound absorption modeling equation, and the acoustic parameters, the input factor, is requiring improvement because of lack of robustness. In this study, we tried to strengthen, standardize, and refine the connectivity between micro (fine structure) and macro (acoustic parameter-related physical properties) characteristics, and improve the consistency with actual NVH performance. As a porous polymer material, polyurethane foam, which is widely used for the interior and exterior of automobiles, is treated as a target material. It is expected that further refining of the correlation between three-dimensional microstructure properties of foam such as pore, throat, strut, window, etc. and acoustic parameters such as air flow resistivity and porosity, etc., can result in more precise sound absorption performance in the modeling formula.
Recent experiments by a team from the West Virginia University focused on how a weightless microgravity environment affects 3D printing using titania foam, a material with potential applications ranging from UV blocking to water purification. ACS Applied Materials and Interfaces published their findings.
Researchers at the University of Bath working in collaboration with industrial partner, Integrated Graphene, have developed a new sensing technique based on graphene foam for the detection of glucose levels in the blood. Since it is a chemical sensor instead of being enzyme-based, the new technology is robust, has a long shelf-life and can be tuned to detect lower glucose concentrations than current systems.
Polyurethane foam (PU foam) is widely used in automotive noise reduction palliatives. As a decoupling insulator its acoustic performance depends on intrinsic properties, called “Biot” parameters. An important decoupling parameter is the apparent stiffness of the PU foam cell structure, as this controls the transportation of vibrational energy, with “softer PU foam” being the preferred option. However, some areas of application, for example in automotive carpet design, requires stiffer PU foam in order to accommodate under foot comfort. For a comprehensive approach to automotive component design, it is necessary to calculate the appropriate spatial PU foam properties ideally without the need for series of prototypes. This paper describes the methods and processes used when compiling and validating a material database capable of predicting the acoustic performance of flat sample or spatially complex 3D component with minimal prototype manufacture.
This recommended practice describes the materials, related equipment, and particular processing techniques utilized in process science curing of composite hardware where pressure is imparted specifically to the resin of curing composites. Included as Appendix "A" to this ARP is a discussion of the particular techniques developed for a processing science philosophy which has consistently produced void and porosity-free, large area, thick composite structures.
Light weighting in modern automotive powertrains call for use of plastics (PP, PA66GF35) for cam covers, intake manifolds and style covers, and noise encapsulation covers. Conventionally, in early stage of design these components are evaluated for static assembly loads & gasket compression loads at component level. However, engine dynamic excitations which are random in nature make it challenging to evaluate these components for required fatigue life. In this paper, robust methodology to evaluate the fatigue life of engine style cover assembly for random vibration excitations is presented. The investigation is carried out in a high power-density 4-cylinder in-line diesel engine. The engine style cover (with Polyurethane foam) is mounted on cam cover and the intake manifold using steel studs and rubber isolators to suppress the radiated noise. The style cover mounting ribs experience higher dynamic bending stresses due to the overhang of the mounting bosses from cam cover and intake manifold. The random vibration fatigue analysis provides good assessment for fatigue life of these components. The Computer Aided Engineering (CAE) results show good correlation with durability testing. The present work also covers the FE modelling techniques, material data and damping consideration in simulation for plastics for vibration fatigue analysis.
The stair phase coding method is an important phase unwrapping method, but needs to project and capture many fringe patterns. Therefore, to reduce the number of fringe patterns, we propose a stair phase coding method based on arc cosine with only four patterns. We project and capture a set of three-step phase-shift sinusoidal fringe patterns and a cosine pattern encoding stair phase, and then we compute the wrapped phase and background light from the three-step phase-shift sinusoidal fringe patterns, normalized cosine pattern can be estimated via background light, and the cosine pattern encoding stair phase. Arc cosine calculation is applied to the normalized cosine pattern to obtain the stair phase, then the fringe order is determined from the stair phase. A semi-periodic fringe order correction algorithm based on the dilation image processing technique is proposed to ensure the accuracy of fringe order. The continuous phase is obtained from the wrapped phase and the fringe order. Experiments are carried out to verify the performance of the proposed method using a face model and a foam board with two hollows. The results show that our algorithm can achieve accurate three-dimensional measurement with only four patterns.
Weight reduction in automotive applications have led to the processing of thermoplastic polymers by foam injection molding. The density of the foamed polymer can be reduced up to 20%. Whilst, work has been reported on the weight reduction of the foamed polymer by using different types of blowing agent technologies, there has been limited studies in the areas of the sound transmission loss and sound attenuation properties of these materials. The present study is intended to understand the effect of chemical blowing agent (CBA) on the properties of polypropylene. The molded specimens were characterized using density, Differential scanning colorimetry (DSC), Thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FT-IR) and sound transmission loss (STL) measurements. Specimens were also tested for tensile properties, flexural properties, Izod impact strength and Heat deflection temperature (HDT) as per standard test protocol. Cell structures were observed using stereo microscope. The obtained results indicated significant improvement in sound transmission loss at 3% and 5% chemical blowing agent dosage. This improvement was accompanied with a reduction in the density.
Electrification is one of the megatrends across the industries, like electric vehicles, electric aircraft, etc. which needs advancement in power electronics component technology. As technology advances in miniaturization of power electronics, thermal-management issues threaten to limit the performance of these devices. These may force designers to derate the device performance and ultimately these compromise in design may increase the size & weight of the application. One of the technologies capable of accomplishing these goals employs a class of materials know as metal foam. Metal foams are lightweight cellular materials inspired by nature. The main application of metal foams can be grouped into structural and functional and are based on several excellent properties of the material. Structural applications take advantage of the light-weight and specific mechanical properties of metal foam. Functional applications are based on a special functionality, i.e. a large open area in combination with very good thermal conductivity for heat dissipation. This paper reports the results of an experimental investigation on the heat transfer performance of metal foam and solid metal under forces & natural convection. Experiments have been conducted with aluminum metal foams in two different pore densities and solid aluminum using air as fluid medium. Pore densities of metal foam used for experiments are 10PPI & 20PPI. Experiments are performed for two different flow rates using two speed fan and two power rating (heat load) using heating coil as source. Thermocouple were placed at heat source side and on opposite side of samples to effectively measure the surface temperature. Surface temperature of samples are measured and compared for all the samples. Experiment results shows that same thermal response can be achieved with 50% smaller size of foam as compared to solid aluminum along with weight benefit (~5x) under forced convection.
The open-cell polyurethane foam has a significant influence on the dynamic response of the Seat-occupant Coupling System (SoCS). Hardness, as an important property of foam, significantly impacts the compliance of human body support. Therefore, it is necessary to study the effects of varying foam hardness on the vibration transmitted to the human body. In this study, the effects are investigated by combining the test and simulation. In the test, the vibration transmission characteristic is measured and analyzed using Transmissibility, Seat Effective Amplitude Transmissibility (SEAT) value, and Weighted Root-Mean-Square value (W-RMS). In addition, the properties o dynamic stiffness and damping are also discussed. In the simulation, combined with the test results of dynamic stiffness/damping, a three-degree-of-freedom (3-DOF) model of SoCS is established. Meanwhile, by introducing goodness of fit, the consistency of simulation and test results is evaluated and quantified. The results indicate that (1) With increasing foam hardness on the seat pan, the resonance frequency almost remains constant, and the transmissibility associated with the resonance increases. (2) When the foam becomes harder, the damping characteristic also changes obviously, which causes that the vibration of SoCS attenuates faster and the SEAT value and W-RMS also go smaller. (3) Moreover, both the dynamic stiffness and damping decrease with the increasing foam hardness, which reveals they are consistent in this case. (4) The simulation results are in good agreement with the test results, which further indicate the validity of the proposed 3-DOF model.
Integration of acoustic material concepts into vehicle design process is an important part of full vehicle design. The ability to assess the acoustic performance of a particular sound package component early in the design process allows designers to test various design concepts before selecting a final solution and long before a design freeze. This paper describes an innovative acoustic material concept which is easily integrated in a design process through the use of vibro-acoustic simulation and a database of intrinsic properties of acoustic materials: The Biot Parameters. Biot parameters are widely used in simulation in many industries (and used the most in the automotive industry) to describe the physical interactions between the acoustic waves travelling through foams, fibers or homogeneous metamaterials and the solid and fluid phase of these poro-elastic materials. Therefore, the surface absorption, the insertion loss and the added damping provided by the acoustic treatments on the base plate can all be predicted accurately. Simulation can be performed at component and full vehicle level using Biot parameters since these are the intrinsic properties of the porous material, the same way Young’s Modulus is an intrinsic property of steel. Furthermore, Biot parameters can be directly used in FEM (Finite Element Method), BEM (Boundary Element Method) and SEA (Statistical Energy Analysis) thanks to the existence of porous finite elements or the use of TMM (Transfer Matrix Method). This paper introduce a new acoustic material concept which provides a combination of absorption, transmission loss and added damping on the panel it is attached to. It has shown unique vibro-acoustics performance when tested on a German car manufacturer flagship vehicle and provides the ability to reduce the space needed for sound package component compared with classical solutions. It is manufactured by impregnating a fraction of total thickness of a PU foam. This results in two acoustic layers, one light foam and the other a heavy and high damping layer. A description of the Biot parameter measurements of each layer and test results for each sample tested along with standard deviation are provided. Finally, a simulation analysis using TMM is performed to assess the airborne and structureborne acoustic performance of this new unique material.
There are many opportunities for lightweighting with ductile iron castings. Current research shows ductile iron castings free of massive carbides can be achieved at under 2 mm (0.080”) through alloying or process changes which means that significant weight reductions are possible. In fact, for aluminum components over 4 mm thick, ductile iron may provide lightweighting opportunities at a cost savings. However, the conventional guidelines for casting design are inadequate when using ductile iron at dimensions less than the typical machine stock. This paper will discuss the current research on thin walled ductile iron, when it is superior to aluminum, design considerations, and current DOE SBIR funded research efforts to address these inadequacies. Research results on efforts to quantify and improve surface roughness in expanded polystyrene for lost foam casting are also discussed.
During the vehicle design state, vehicle noise and vibration are taken into consideration. The tire is a large contributor to the noise and vibration experienced inside the vehicle cabin. Any unevenness or asperities in the road cause the tire structure to vibrate, which in turn causes components in the vehicle to vibrate and generate noise. It is common in the industry to use foam inserts inside the tire air cavity that reduces the noise generated. This foam is typically intended to reduce a specific resonance in the tire-the resonance due to the air cavity. Recently, there is interest in using foam as a structural damper to reduce structural resonances in the tire. A new analytical tire model for determining the effect that structural damping foam has on the noise and vibration characteristics of the tire has been developed. The theoretical formulation of this model is presented, as well as comparison with experiments and a parametric analysis of the model. The model shows good agreement with experimental results and also gives some additional insights into how the tires’ response can be altered by different design parameters.
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