M. Mohamed

Testing and Evaluation of Polyurethane-Based GFRP Sandwich Bridge Deck Panels with Polyurethane Foam Core

AbstractThis paper presents the evaluation of an innovative low-cost small-scale prototype deck panel under monotonic and fatigue bending. This new system introduces a trapezoidal-shaped polyurethane foam core with a thermoset polyurethane resin that has a longer pot life to facilitate the infusion process. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness. The panels consist of two glass fiber–reinforced polymer (GFRP) facings with webs of bidirectional E-glass–woven fabric that are separated by a trapezoidal-shaped low-density polyurethane foam. The GFRP panels were manufactured using a one-step vacuum-assisted resin transfer molding process. The specimens studied were constructed in the Composite Manufacturing Laboratory in the Mechanical and Aerospace Engineering Department at Missouri University of Science and Technology. Small-scale prototype deck panels were tested both statically and dynamically in four-point bending to inves...

Experimentation and simulation of moisture diffusion in foam-cored polyurethane sandwich structure

The moisture diffusion behavior of two-part thermoset polyurethane neat resin, woven E-glass fiber-reinforced polyurethane face sheet, closed-cell rigid polyurethane foam core and their corresponding sandwich specimens was investigated in this study. The vacuum-assisted resin transfer molding process was used to manufacture the polyurethane sandwich panels. Open-edge moisture diffusion experiment was conducted for sandwich panel and its constituents by immersing each type of samples in distilled water at room temperature for nearly seven months. Moisture diffusivities and solubility for neat resin, face sheet and foam core specimens were characterized according to the experimental analysis. The moisture diffusion behavior for closed-cell polyurethane foam was found to deviate significantly from classical Fick’s law, and a multi-stage diffusion model was thus proposed to explain this deviation using a time-dependent diffusivity scheme. A user-defined subroutine was developed to implement this scheme into the commercial finite element analysis code ABAQUS. A three-dimensional dynamic finite element model was developed to predict the moisture diffusion behavior in neat resin, face sheet, foam core and sandwich specimens. This finite element model was then validated by comparing simulation results with experimental findings.

Manufacturing and evaluation of polyurethane composite structural insulated panels

Composite materials are increasingly used in applications of civil infrastructure and building materials. The new generations of two-part thermoset polyurethane resin systems are desirable materials for infrastructure applications. This is due to high impact resistance, superior mechanical properties, and reduced volatile organic compounds when compared to the conventionally used resin systems such as vinyl ester and polyester. Glass fiber-reinforced two-part polyurethane composites and low-density polyurethane foam are used to design and manufacture composite structural insulation panels using vacuum assisted resin transfer molding process for temporary housing applications. Using these types of composite panels in building construction will result in cost-efficient, high-performance products due to inherent advantages in design flexibility. Use of core-filled composite structures offers additional benefits such as high strength, stiffness, lower structural weight, ease of installation and structure replacement, and higher buckling resistance than the conventional panels. Energy efficiency is known to be inherently better with the core-filled composite panel than in a metallic material. The panels can be designed to resist the required loads, and the study aims to evaluate the ability of lab scale tests and models to predict part quality in full-scale parts. Furthermore, it discusses the manufacturing challenges. Flexural tests and energy consumption evaluations were performed on these structural components. Finite element simulation results were used to validate the flexural experiment findings.

Manufacturing and Performance Evaluation of Polyurethane Composites Using One-Part and Two-Part Resin Systems

Polyurethane (PU)-based composites show superior performance compared to polyester and vinylester composites. The demand for PU composites is increasing in high technology as well as conventional applications such as infrastructure and automobile. In this study, glass fiber reinforced composite laminates using one-part and two-part PU resin are manufactured using vacuum-assisted resin transfer molding (VARTM) process. A new generation two-part thermoset PU resin system is investigated and compared with commercial one-part PU resin systems. The mechanical performance of glass fiber reinforced composites manufactured using two different PU resin systems is evaluated. Tensile and flexure tests are conducted on both neat resin and glass/PU composites. Low-velocity impact tests are performed on both types of glass fiber reinforced PU composite specimens. Mechanical properties including strength and modulus were measured and analyzed for the two resin systems. Differential scanning calorimetry (DSC) is used to study the cure behavior of both resin systems. A Brookfield LVDV-II programmable rotational type viscometer is employed to study the viscosity profiles of the resin systems. The influence of resin properties on the overall performance of glass fiber reinforced composites is discussed.

Impact Characterization of Polyurethane Composites Manufactured Using Vacuum Assisted Resin Transfer Molding

Glass fiber reinforced composites are finding various applications due to their high specific stiffness/strength, and corrosion resistance. Vacuum assisted resin transfer molding (VARTM) is one of the commonly used low cost composite manufacturing processes. Polyurethane (PU) resin system has been observed to have better mechanical properties and higher impact strength when compared to conventional resin systems such as polyester and vinyl ester. Until recently, PU could not be used in composite manufacturing processes such as VARTM due to its low pot life. In the present work, a thermoset PU resin systems with longer pot life developed by Bayer MaterialScience is used. Glass fiber reinforced PU composites have been manufactured using one part PU resin system. Performance evaluation was conducted on these composites using tensile, flexure and impact tests. Finite element simulation was conducted to validate the mechanical tests. Results showed that PU composites manufactured using novel thermoset PU resins and VARTM process will have significant applications in infrastructure and automotive industries.© 2012 ASME

Effect of salt water exposure on foam-cored polyurethane sandwich composites

This study investigated the effect of moisture absorption on the mechanical performance of polyurethane sandwich composites. The core material was a closed cell polyurethane foam. Face sheets were made of E-glass/polyurethane composite laminates. Vacuum-assisted resin transfer molding process was used to manufacture specimens for testing. The foam core, laminates, and sandwich composites were submerged in salt water for prolonged periods of time. Mechanical property degradation due to moisture absorption for each constituent was evaluated. Compression test was performed on the foam core samples. Laminates were evaluated by three-point bending tests. The interfacial bond strength in the sandwich structure was evaluated by double cantilever beam mode-I interfacial fracture test. The testing results revealed that the effect of salt water exposure on the compressive properties of the foam core is insignificant. The flexural modulus of polyurethane laminates degraded 8.9% and flexural strength degraded 13.0% after 166 days in 50% salinity salt water at 34°C conditioning. The interfacial fracture toughness of polyurethane sandwich composites degraded 22.4% after 166 days in 50% salinity salt water at 34°C conditioning.