High-density Rigid Polyurethane Foam Research Articles

A dynamic constitutive model for high-density rigid polyurethane foam subjected to impact loading

This study experimentally and numerically investigated the dynamic response of high-density rigid polyurethane foam (RPUF). Firstly, drop-weight tests were conducted under three impact velocities, 2.42 m/s, 3.43 m/s, and 4.85 m/s. Test results showed that the dent depth and absorbed energy rise as impact velocity increases. Then the constitutive model for high-density RPUF based on an ideal elastoplastic constitutive model is proposed based on the measured mechanical properties, including quasi-static uniaxial compression tests, quasi-static uniaxial tensile tests, triaxial confining pressure tests, and split-Hopkinson pressure bar tests. Finally, the numerical simulation of the drop-weight tests was conducted. It was shown that the proposed dynamic constitutive model can accurately describe the dynamic performance of a high-density RPUF subjected to impact loading.

Design and mechanical analysis of shear thickening fluid/polyurethane composite sandwich

In this paper, high density rigid polyurethane foam is used as sandwich skeleton and shear thickening fluid as material core. A shear thickening fluid/polyurethane sandwich structure with light impact resistance was designed and fabricated. High strain rate impact test was carried out. It was found that STF-2/PU reached the peak load of 4978N in 13 ms after receiving 20 J impact energy, and the energy absorption ratio was as high as 43%. The shear thickening fluid/polyurethane honeycomb sandwich foam prepared by secondary foaming process has stable structure and can effectively absorb impact energy to achieve good protection effect.

Mechanical performance and cushioning energy absorption characteristics of rigid polyurethane foam at low and high strain rates

This study elucidates the mechanical response of rigid polyurethane foam (RPUF) at different strain rates and densities. A series of quasi-static and dynamic loading tests on the RPUFs were performed to determine the deformation modes, stress-strain curves, and effects on density, strain rate, and energy absorbing performances. Consequently, the static compressive behavior of RPUF significantly depends on density and strain rate, while the dynamic compressive behavior of RPUF significantly depends on density. However, the effect of strain rate is not evident at high strain rates (500 s−1–2500 s−1). The elastic modulus, compressive strength, and yield stress of RPUF increase with a rise in density. The experimental results show that the compressive strength is enhanced at a high strain rate loading when compared with that at quasi-static loading. Based on the measured stress-strain curves, the variation in energy absorption and efficiency with respect to RPUF density was studied. The typical damage mechanism of RPUF with different densities was investigated via scanning electron microscopy. Cell wall buckling is the prominent failure mode in the high-density RPUF; however, the main failure modes of low-density RPUF are wrinkling and stretching of cell faces.

Investigating relative density effects on quasi-static response of high-density Rigid Polyurethane Foam (RPUF)

This study aims at characterisation of various densities of Rigid Polyurethane Foam (RPUF) under quasi-static tension and compression. The density of foam is key parameter in selection of suitability for structural applications. Various densities of RPUF are synthesised using commercial grade Polyols and Methylene diphenyl isocyanate (MDI). The ratio of mixing both constituents was maintained at 1:1.15 for polyol and MDI respectively. Free rise density of the foam was achieved at 234 kg/m3 and is considered the baseline density for comparison. The higher than baseline densities were achieved by blowing the mixture into a mould with variable pouring times and three densities in the range of 252 kg/m3, 303 kg/m3 and 353 kg/m3 were achieved. The tensile and compression specimens were prepared from the manufactured blocks. SEM images were taken from the blocks of various densities and uniform cell patterns were observed for all densities. The specimens were then tested under compressive and tensile loads. It was found that the specimen exhibit consistency in results and the density affects the mechanical properties directly. Optimum density of foam for energy absorption capability of RPUF based on specific work done is also estimated. A phenomenological model based on relative density of foam was developed to assess material behaviour which can reduce the requirement of test specimens for obtaining a set of particular material properties.

Construction of 3-D realistic representative volume element failure prediction model of high density rigid polyurethane foam treated under complex thermal-vibration conditions

The mechanical failure behaviors prediction model of rigid polyurethane foam (RPUF) treated under complex thermal-vibration conditions was constructed by experiment of tensile properties and numerical simulation for the further analysis of the failure progress and mechanism of RPUF. On the basis of scanning electron microscope (SEM) observation, a realistic representative volume element (RVE) of RPUF was firstly established by means of Voronoi-spherical tessellations. Tensile properties of RPUF treated under different thermal-vibration conditions were measured subsequently. Results of the tensile properties characterization of RPUF suggested that the thermal and vibration treatment on RPUF reduced its tensile strength and fracture elongation decrease due to the chemical degradation of polyurethane (PU) matrix and physical breaking of the foam structure. The tensile constitutive relationship derived from the tensile experiments was assigned to the realistic RVE, and the thermal-vibration failure prediction model of RPUF was further constructed in the ABAQUS software. The numerical simulation results revealed that the stress concentrations appeared and extended along with the weakness regions of RPUF structure under the external load. The stress-strain curves of thermal-vibration treated RPUF obtained from the prediction model were in well agreement with the experimental results, and the average computation error was less than 3%. It indicated that the prediction model can accurately describe the failure progress of thermal-vibration treated RPUF. This work provides ideas for the design of the foam materials with high thermal-vibration aging resistance by numerical simulation in the future.

Calculation of Boil-Off Gas (BOG) Generation of KC-1 Membrane LNG Tank with High Density Rigid Polyurethane Foam by Numerical Analysis

Abstract Recently, a new type of LNG tank named “KC-1 membrane LNG tank” has been developed by Korean Gas Corporation (KOGAS), and Samsung Heavy Industries (SHI) is currently building KC-1 membrane type LNG carriers. Unlike other LNG tanks, the KC-1 membrane LNG tank has a single-insulation structure rather than a double-insulation structure. For a given tank’s boundary condition, heat transfer analysis is performed from the external to the internal environment of the LNG tank by numerical simulation for three tanks. In each tank, the main thermally resistant layer of insulation is assembled with a High density rigid Polyurethane Foam (H-PUF), which is blown with one of three different types of hydrofluorocarbons-namely-HFC-365mfc, 245fa, and 245fa-e (enhanced). Advantage of such blowing agents is that it has a lower Ozone Depletion Potential (ODP) than HCFC-141b or carbon dioxide (CO2) that has been used in the past as well as having low thermal conductivity. A Reduced Order Model is utilized to a 3-dimensional section of the insulation to calculate equivalent thermal conductivity. The equivalent thermal conductivity of the insulation is then applied to the rest of LNG tank, reducing the size of tank simulation domain as well as computation time. Tank’s two external and internal boundary conditions used are those defined by the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC) and the United States Coast Guard (USCG) conditions. Boil-off Rate (BOR) of the tank that has the insulation with H-PUF blown with HFC-245fa resulted in 0.0927 %/day and 0.0745 %/day for IGC and USCG conditions, respectively.

Mechanical and Thermal Properties of High-Density Rigid Polyurethane Foams from Renewable Resources

Mechanical and Thermal Properties of High-Density Rigid Polyurethane Foams from Renewable Resources

Expandable Graphite For Halogen-Free Flame-Retardant of High-Density Rigid Polyurethane Foams

ABSTRACT We obtained the high-density rigid polyurethane foam (RPUF) filled with expandable graphite (EG) by airtight cast molding, and its fire performance was evaluated. The results show that the LOI values increase linearly with EG content, especially the LOI value of the 20 wt% EG-filled RPUF composites increases rapidly to 39.5% from 22.5% of pure RPUF. When the pure RPUF was burned, no clear transition process between burning spots and virgin material is observed. But when the EG/RPUF composite was burned, EG produced high-volume expanded graphite and covered the surfaces of the materials, which can prevent combustible gases from feeding the flame, and it also separates oxygen from the burning material efficiently. The thermal degradation of foam was investigated using thermogravimetric analysis (TGA). The result shows that the thermo-oxidative degradation of pure RPUF takes place in the range of 220–350°C and 450–650°C, respectively. The thermal stability of RPUF composites increased slightly when it contained 20 wt% EG. The mechanical and electrical properties of EG/RPUF were also discussed. Generally, addition of EG resulted in a slight decrease in the mechanical properties and no influence on the electrical conductivity.

Development of a model for occipital fixation--validation of an analogue bone material.

Several implant systems may be used to fuse the skull to the upper cervical spine (occipitocervical fusion). Current biomechanical evaluation is restricted by the limitations of human cadaveric specimens. This paper describes the design and validation of a synthetic testing model of the occipital bone. Data from thickness measurement and pull-out strength testing of a series of human cadaveric skulls was used in the design of a high-density rigid polyurethane foam model. The synthetic occipital model demonstrated repeatable and consistent morphological and biomechanical properties. The model provides a standardized environment for evaluation of occipital implants.

Composition for reinforced and filled high density rigid polyurethane foam products and method of making same: Deaver, D.T. (Tecnik International Corporation) US Pat 4 005 035 (25 January 1977)

Composition for reinforced and filled high density rigid polyurethane foam products and method of making same: Deaver, D.T. (Tecnik International Corporation) US Pat 4 005 035 (25 January 1977)