Fiber Reinforced Polyurethane Foam Research Articles

The Effect of Damages on Modal Frequencies of Flat Glass Fiber Reinforced Polyurethane Foam Sandwich Structures

The Effect of Damages on Modal Frequencies of Flat Glass Fiber Reinforced Polyurethane Foam Sandwich Structures

Application of microwave holographic subsurface technology for non-destructive testing of reinforced polyurethane foam

Glass fiber Reinforced Polyurethane Foam (RPUF) has found wide application primarily in the aerospace and construction industry due to its outstanding properties. Unlike pure non-reinforced Polyurethane Foam (PUF), it has increased strength characteristics and at the same time retains unique heat and sound insulation properties. The paper considers the features of reinforced polyurethane foam examination in the Microwave (MW) range. It is shown that there is a significant difference in the recorded MW images compared to pure polyurethane foam. This is expressed primarily in the fact that the reinforcing fibers have a dielectric constant that is different from enclosing polyurethane foam, which leads to scattering and reflection of the incident electromagnetic wave on them. Experimental studies have shown that for RPUF, in contrast to PUF, there is an optimal wavelength range in which the contrast of defects against the background of glass fiber reflections is of the greatest value. An experimental comparison of two methods of examination back-scattering and forward-scattering methods was also carried out for RPUF. It is shown that the forward-scattering technology of measurements, if it can be implemented, has certain advantages since allows reducing the contrast of background reflections from the reinforcing fibers.

Application of microwave holographic subsurface technology for non-destructive testing of reinforced polyurethane foam

Glass fiber Reinforced Polyurethane Foam (RPUF) has found wide application primarily in the aerospace and construction industry due to its outstanding properties. Unlike pure non-reinforced Polyurethane Foam (PUF), it has increased strength characteristics and at the same time retains unique heat and sound insulation properties. The paper considers the features of reinforced polyurethane foam examination in the Microwave (MW) range. It is shown that there is a significant difference in the recorded MW images compared to pure polyurethane foam. This is expressed primarily in the fact that the reinforcing fibers have a dielectric constant that is different from enclosing polyurethane foam, which leads to scattering and reflection of the incident electromagnetic wave on them. Experimental studies have shown that for RPUF, in contrast to PUF, there is an optimal wavelength range in which the contrast of defects against the background of glass fiber reflections is of the greatest value. An experimental comparison of two methods of examination back-scattering and forward-scattering methods was also carried out for RPUF. It is shown that the forward-scattering technology of measurements, if it can be implemented, has certain advantages since allows reducing the contrast of background reflections from the reinforcing fibers.

현무암 섬유 보강 폴리우레탄폼의 열적 성능 및 극저온 환경에서의 기계적 특성 평가

LNG CCS which is a special type of cargo hold operated at –163℃ for transporting liquefied LNG is composed of a primary barrier, plywood, insulation panel, secondary barrier, and mastic. Currently, glass fiber is used to reinforce polyurethane foam. In this paper, we evaluated the possibility of replacing glass fiber-reinforced polyurethane foam with basalt fiber-reinforced polyurethane foam. We conducted a thermal conductivity test to confirm thermal performance at room temperature. To evaluate the mechanical properties between basalt and glass-fiber-reinforced polyurethane foam which is fiber content of 5 wt% and 10 wt%, tensile and an impact test was performed repeatedly. All of the tests were performed at room temperature and cryogenic temperature(-163℃) in consideration of the temperature gradient in the LNG CCS. As a result of the thermal conductivity test, the insulating performance of glass fiber reinforced polyurethane foam and basalt fiber reinforced polyurethane foam presented similar results. The tensile test results represent that the strength of basalt fiber-reinforced polyurethane foam is superior to glass fiber at room temperature, and there is a clear difference. However, the strength is similar to each other at cryogenic temperatures. In the impact test, the strength of PUR-B5 is the highest, but in common, the strength decreases as the weight ratio of the two fibers increases. In conclusion, basalt fiber-reinforced polyurethane foam has sufficient potential to replace glass fiber-reinforced polyurethane foam.

Mechanical Performance Degradation of Glass Fiber-reinforced Polyurethane Foam Subjected to Repetitive Low-energy Impact

Polyurethane foam (PUF) has excellent thermal insulation performance owing to its closed cellular solid structure. Additionally, this microstructural characteristic provides outstanding impact absorption performance. Owing to these advantages, PUF is widely adopted in transportation applications. From the viewpoint of use in practical applications, it is necessary to evaluate the residual strength after repetitive low-energy impacts on the structure. Thus, in the present study, we investigated the effects of repetitive low-energy impact on mechanical behavior of glass fiber-reinforced PUF. After the free-falling type repetitive impact test, a series of compressive tests were performed to investigate the effect of impact conditions on the compressive performance. As a result, the critical impact energy causing degradation of the impact and compressive performance of RPUF was 1,092 - 1,228 J/m2. In the impact performance, the peak stress, impact duration, and peak strain decreased by 13.5%, increased by 28.5%, and increased by 35.2%, respectively, after 80 repetitions of a 1,500 J/m2 impact. Moreover, under the same impact condition, the elastic modulus decreased by 44.5% compared to that of the intact specimen.

Effect of Repetitive Impacts on the Mechanical Behavior of Glass Fiber-reinforced Polyurethane Foam

In a cryogenic storage structure, the insulation system is in an environment in which fluid impact loads occur throughout the lifetime of the structure. In this study, we investigated the effect of repetitive impact loading on the mechanical performance of glass fiber-reinforced polyurethane foam. The repeated impact loading test was conducted in accordance with the required impact energy and the required number of repetitive impacts. The impact behavior of glass fiber-reinforced polyurethane foam was analyzed in terms of stress and displacement. After the impact test, the specimen was subjected to a compression test to evaluate its mechanical performance. We analyzed the critical impact energy that affected mechanical performance. For the impact conditions that were tested, the compressive strength and elastic modulus of the polyurethane foam can be degraded significantly.

Experimental characterization of temperature dependent dynamic properties of glass fiber reinforced polyurethane foams

The static and dynamic compressive behaviors of glass fiber-reinforced polyurethane foams were characterized under cryogenic temperature conditions to help identify the essential design and parameters required to model the response of the foam accurately under the various loading conditions encountered in liquefied natural gas cargo containment systems. The material properties of polyurethane foams with varying concentrations and orientations of the glass fiber continuous strand mat were characterized by quasi-static, dynamic mechanical analysis (DMA), and low velocity impact testing. The testing results showed increased strength with increasing density and strain rate, as well as similar failure modes independent of the strain rate. In addition, the glass fibers dominated the DMA behavior and a glass transition temperature at or above 130 °C was observed for all foam varieties. Overall, the glass fiber reinforced polyurethane foam showed the typical static and dynamic compressive behaviors of foams at both room and cryogenic temperatures.

Protective rigid fiber-reinforced polyurethane foam composite boards: Sound absorption, drop-weight impact and mechanical properties

Polyurethane foam has been develocped for years. In the past, the most study is focused on one function of Polyurethane foam including noise absorption, thermal protection, and mechanical impact as well as cushioning properties, and thus interdisciplinary functions of these foam boards become an innovation research. Therefore, the objective of study is to develop the multifunctional protective composite boards which are suitable for diversified environments. In this study, the carbon fibers (CF) and glass fibers (GF) are used as reinforcements for PU composite boards which are denoted as CFR-PU and GFR-PU respectively. The composite boards are made with different thickness and different contents of reinforcing fibers. The drop-weight impact test adopts a circular drop weight that falls from a certain height in order to observe the deformation mechanism of the boards. Different fracture modes that are caused by the bursting, compression, drop-weight impact, and puncture resistance tests are then examined. The test results indicate that the CFR-PU and GFR-PU fiberreinforced composite boards have a satisfactory impact load of 90 % and a favorable absorption coefficient at a certain frequency, and also have improved mechanical properties.

Polymeric foams for cryogenic temperature application: Temperature range for non-recovery and brittle-fracture of microstructure

In the present study, low-temperature material characteristics of polyurethane foam, glass fiber-reinforced polyurethane foam, and polyisocyanurate foam were investigated. These foams are key candidate materials for use in membrane-type liquefied natural gas insulation systems. Liquefied natural gas insulation systems should be able to withstand severe environmental conditions, such as fluid induced impact loading under cryogenic temperatures. For the robust design of insulation system, both failure characteristics and deformation recovery capacity of the materials must be evaluated. Therefore, the failure characteristics and the deformation recovery ratio of the foams were investigated at various temperatures and strain rate levels. The present study revealed that the fracture behavior and the recovery ratio were significantly affected by decreases in temperature. As a newly obtained insight, it has been found that the recovery ratio for all tested materials significantly decreased at −163°C. This finding is the opposite of the behavior that typically occurs at low temperatures. In particular, polyurethane foam specimen after experiment at the temperature of −163°C was easily broken into pieces even under the application of small loads. In addition, it has been revealed that polyisocyanurate foam showed superior mechanical characteristics at cryogenic temperatures owing to the ring structure of isocyanurate.

Cryogenic impact resistance of chopped fiber reinforced polyurethane foam

Liquefied natural gas (LNG) is primarily carried by a membrane type LNG ship, which has a cryogenic containment system composed of dual tightness barriers and insulation boards. The insulation board should have cryogenic reliability as well as high thermal insulation for the safe and efficient transportation. Sandwich construction and fiber reinforced polyurethane foam (PUF) are generally used for the insulation board and the core materials, respectively. During the operation of the LNG ship, cavitation and sloshing could generate an impact load on the PUF, which is an ongoing concern in the ship building industry.Therefore, the cryogenic impact resistance of the chopped E-glass fiber reinforced PUF was investigated with respect to the amount of chopped fibers. The drop weight impact test was conducted at a cryogenic temperature of −196°C using liquid nitrogen. The applied maximum impact pressure, permanent strain and damage factor were measured to assess the damage caused by the impact test, from which the critical impact energy was investigated. From the experimental results, a criterion was suggested to assess the cryogenic impact resistance of the PUF and it was determined that the chopped fiber reinforcement significantly increased the impact resistance of the PUF at the cryogenic temperature.

Effect of mixing conditions on the morphology and performance of fiber-reinforced polyurethane foam

Polyol derived from soybean oil was used as a natural source preparation to create an environmentally friendly polyurethane foam. In order to stiffen these foams, wood fibers were added to provide reinforcement at low cost, while preserving the environmental friendly nature of the material. Mixing is a crucial step in the manufacture of reinforced foams and determines the fiber distribution and cell structure and hence the performance of the material. In this study, the effect of stirring variables on the mechanical properties of polyurethane foams was investigated and foams made using hand mixing were compared to foams made with a mechanical stirrer. Cell morphologies of the reinforced foams were characterized using scanning electron microscopy, X-ray computed tomography, and 3D stereo microscopy. The mechanical performance of the reinforced foam was essentially independent of stirring time and mainly depended on the variation in stirring rate. For foams made with high fiber fractions using a mechanical stirrer, the fibers were not as effective in increasing the compressive strength and modulus as they were in foams prepared by hand stirring. This suggests that mechanical stirring causes damage to the fibers, particularly at high fiber content.

Cryogenic characteristics of chopped glass fiber reinforced polyurethane foam

Liquefied natural gas (LNG) is mainly carried by membrane type LNG ships, whose cargo containment system is composed of dual tightness barriers and two insulation boards. The insulation board should have not only cryogenic reliability against thermal load, but also high thermal insulation performance for safe and efficient transportation of LNG. Although polyurethane foam (PUF) has been widely used for the insulation board due to its low production cost and relatively good thermal and mechanical properties, the cryogenic reliability of PUF is a remaining concern in marine fields due to its brittleness at cryogenic temperatures.In this work, the PUF was reinforced with chopped E-glass fiber because of its good dispersion and distribution characteristics. The compression, tension and the fracture toughness test were conducted with respect to the amount of the chopped E-glass fiber both at the room (25°C) and cryogenic (−150°C) temperatures. From the experimental results, it was found that the chopped E-glass fiber reinforcement increased the fracture toughness of the PUF much, especially at the cryogenic temperature. Therefore, the PUF reinforced with chopped glass fibers will improve much the reliability of the LNG cryogenic containment system during the voyage of LNG ships.

Optimization of Parameters in Fiber Reinforced Polyurethane Composited Reaction Injection Molding

In order to explore effects of various processing parameters on the mechanical properties of jute fiber reinforced polyurethane foam composites, jute fiber reinforced polyurethane composites were prepared by variable fiber reinforced reaction injection technology. The influence of jute fiber contents, fiber length, mold pressure and fiber modification treatment to the impact toughness was analyzed by orthogonal test in this paper. The microstructure and fracture micrograph of impact fracture specimens were studied with scanning electron microscope (SEM). The results showed that the best impact performance was obtained while fiber content was 10%, fiber length was12.5mm, mold pressure was 80tons, and jute fibers were modified by alkali. Furthermore, the result was compared with the corresponding research of glass fiber and carbon fiber reinforced polyurethane composites, and provided a theoretical basis for the application of the fiber reinforced polyurethane foam composites.

A feasibility study of polyurethane composite foam with added hardwood pulp

Polyurethane (PU) composite foams were prepared by pour method with soy-based polyol (soyol). Foams were tested for the evaluation of mechanical properties and cell morphologies as a portion of wood fiber present. Thermal behaviors as well as foam morphology were investigated. Scanning electron microscopy results exhibited that PU composite foam had improved cell size due to the presence of wood fiber. Thermal gravimetric analysis and differential scanning calorimetry results clearly showed the most substantial increase of the glass transition temperature (Tg) and decrease of the decomposition temperature (Td) in the fiber reinforced PU foam. PU composite foam had no influence on compressive strength; however, it had caused slight reduction in tensile strength. PU composite foam displayed a broad distribution of inter-domain spacing associating with morphological changes.

Characterization of the Compressive Behavior of Glass Fiber Reinforced Polyurethane Foam at Different Strain Rates

A glass fiber reinforced polyurethane foam (R-PUF), used for thermal insulation of liquefied natural gas tanks, was characterized to determine its compressive strength, modulus, and relaxation behavior. Compressive tests were conducted at different strain rates, ranging from 10−3 s−1 to 10 s−1 using a servohydraulic material testing system, and from 40 s−1 to 103 s−1 using a long split Hopkinson pressure bar (SHPB) designed for materials with low mechanical impedance such as R-PUF. Results indicate that in general both Young’s modulus and collapse strength increase with the strain rate at both room and cryogenic (−170°C) temperatures. The R-PUF shows a linearly viscoelastic behavior prior to collapse. Based on time-temperature superposition principle, relaxation curves at several temperatures were shifted horizontally to determine Young’s relaxation master curve. The results show that Young’s relaxation modulus decreases with time. The relaxation master curve obtained can be used to convert to Young’s modulus at strain rates up to 103 s−1 following linearly viscoelastic analysis after the specimen size effect has been considered.

Acoustic characteristics of unidirectionally fiber-reinforced polyurethane foam composites for musical instrument soundboards.

Unidirectionally fiber-reinforced composites for the soundboard of musical instruments were made using glass fiber or carbon fiber and light-weighted hard polyurethane foam. The vibrational properties and frequency response characteristic of the composites were investigated by changing fibers, volume fraction of fibers and fiber distribution, and the results obtained were compared with those of Sitka spruce for soundboard. The composites, which had 5 to 6 volume percent of carbon fiber filaments distributed uniformly, exhibited almost the same acoustic property as Sitka spruce for soundboard. The results indicated that the acoustic characteristic of wood for soundboard in all audible frequency range could be mostly represented using a simple wood model composed of unidirectionally oriented fibers and porous matrix foam.