REU Site in Advanced Engineered Wood Composites (2004)

Below are abstracts for the projects conducted by the 10 NSF supported REU students. Included with each abstract are the project supervisor and associated graduate students. The abstracts were written by the students. Structural Durability of FRP Drains in Bridge Decks Micah Florea, Tulane University Advisor: Roberto Lopez Anido Fiber Reinforced Polymers (FRP) are quickly becoming the material of choice to solve civil engineering challenges in corrosive environments. In the state of Maine, where deicing salts are generously applied to roadways every winter, conventional steel down spouts used to drain concrete bridge decks are quickly corroded and need constant replacing. Looking to lower maintenance costs, the Maine Department of Transportation has joined efforts with the University of Maine to design an FRP down spout to replace the degraded steel ones. Three identical prototypes were fabricated, embedded in a simulated concrete decking, and were submitted to a series of laboratory tests to ensure structural integrity and to optimize the design for longterm durability. The tests included an ice formation study, dual-ramp compression loading tests based on the AASHTO HS25 loading specification, 100,000 cycle fatigue tests, ultimate compression tests, and reverse push out tests. The prototype proved to be acceptable, but not optimal. The prototype design was slightly modified and the new design described in this report is approved as a safe, functional, and durable drain system to be fabricated and installed in bridge decks throughout the state of Maine. Timber Guardrail Splice Connection Design Chad Gibson, University of Evansville Advisor: William Davids Participating Grad Student: Josh Botting Research into designing an aesthetically pleasing and structurally sound timber reinforced guardrail system at the University of Maine is being sponsored by the New England Transportation Consortium. The project specifies the use of glulam beams, as opposed to the use of solid sawn timbers. The composite design will feature a strip of pultruded E-glass epoxy bonded to the tension side of the guardrail and bonded steel splice connections that will attach the railings to posts. Through modeling with the BARRIER VII program, it is apparent that large tensile forces must be transferred between rail sections. The splice connection design will remain as the central focus of this paper as a result of a tendency for structural failure at these critical locations. From BARRIER VII the projected critical axial load is 40 kips. A splice connection must be designed to transfer the loading across the rail system and be appropriately evaluated in a tension test. The connection, which has been tested, is a steel plate bonded to the FRP and bolted to the splice plate. The critical component of the splice is the steel to FRP bond. In order to assess this bond a test setup has been designed. The results of the test proved comparable to the capacity of standard W-beam guardrails. Extrusion of Wood-Plastic Composites Elizabeth Jordan, University of Connecticut Advisor: Douglas Gardner As an REU student the focus of my project was supposed to be the extrusion of wood-plastic composites involving nylon and pine wood flour. Unfortunately due to several miss haps with the equipment and machinery this project was not carried out. Sue to the fact that my original project did not pull through I have done a variety of things this summer and I have learned a great deal too. Although it may not sound like a lot I have also been able to gain an understanding of lab work and graduate school though the program this summer. This summer I have seen polypropylene and wood flour extrusion as well as masonite and polypropylene extrusion. Our most recent extrusion involving mixtures of polypropylene and wood flour actually came out very well. after successfully making the wood-four polypropylene wood composite we did a four point bending test on our samples. For this we used the Instron 8801 universal testing machine. With these tests we found the maximum loading strength of our boards and then plotted our results. we also used the instron machine to test some commercial boards. We did water soak tests for these. Our results from these boards were also plotted and recorded. By doing these tests I learned how to use the instron 8801 and how to plot and record data in excel. As stated earlier the woodtruder or Wt 94 was out of order for a good portion of the summer. While the machine was down I used the time to write work instructions and to begin a thermal expansion testing project. For the thermal expansion testing project I prepared samples and obtained a set up to test for the thermal expansion of wood-composites in relationship to time. Before I started my thermal expansion project and during the time that the extruder was still broken I wrote work instructions and helped other students with their projects. After all of this I have no real results to show other than the few tests that we just completed but I did gain a great deal of experience. Even though I did not get to finish my project I learned how research can be unpredictable and how problem solving a key aspect of it all. Multifunctional Reinforcements for Conventional Wood Composites: Lateral Nail Test Katherine Jordan, University of Connecticut/Materials and Metallurgy Engineering Advisor: Ciprian Pirvu Conventional oriented strand board(OSB) is commonly used in construction. In certain areas that are prone to hurricanes, high winds, and high humidity, such as coastal areas, traditional OSB structures become weakened where they are connected to the wall studs. By desiging an effective edge protection system, moisture can be prevented from entering the wood compostie and causing deterioration. Also, the reinforcment should increase the dimensional stability and connector durability of the compostie. During this project, eight different types of reinforcement were tested for lateral nail holding strengh. These reinforcements were designed to prevent moisture from entering the wood composite at the connection joints and to increase the nail holding strength of the composite. In order to determine which reinforcements performed the best under both wet and dry conditions, a lateral nail test was performed on each type of sample under both wet and dry conditions. The samples were composed of Polyester Resin or Vinyl Ester Resin, Regular OSB and either, Glass Fabric, Aramid Fabric, Chopped Strand Fiberglass, or Fiberglass particles. Advanced OSB, 3/8!inch and 1/2!inch plywood as well as Regular OSB were used as control samples with no reinforcement added. Half of all the samples were soaked in a water bath for twenty-four hours. Each sample was then nialed to a stud and tested on a 22 Kip Instron machine. Together with the results of a nail pullthough test and the moisture content test, the most effective reinforcement can be chosen. From lookinag at the results of the Lateral Nail Test I noticed that Aramid Fabric tended to act well and the _!inch Plywood and Advanced OSB also performed well under wet and dry conditions. Further analysis is necessary in order to determine which method of reinforcement provides the greatest amount of reinforcement at the most reasonable price and with the most efficient application process. Simulating the Failure and Load Deformation Response of Nailed and Bolted Connections Melissa Kahl, Syracuse University, Civil Engineering Advisor: Eric Landis The prospective applications of computer simulations have a tremendous potential for deciphering of real world situations. One such application would be to the failure of wood that is joined together with either a bolt or nail. If the details of this failure of the two dominate fasteners in wood construction were to be correctly predicted, then it would be possible to begin to take necessary steps to prevent this failure. This purpose of this project was to compare the load deformation curve and the aesthetic distortions of the wood produced by the computer simulation, to those produced by the data collected from a simple tension test of these joints. The computer simulation works by first creating a lattice of the wood specimen through the definition of several variables including the thickness of the wood, its width and height, and the number of nodes. The beams and verticals connecting the nodes where the bolt or nail is located are removed to represent the damage caused by these penetrations, creating a notch in the middle of the mesh. The bolted mesh is represented as a square hole in the mesh, as opposed to the nailed mesh that is represented with the beams around the hole curved to simulate the distorted grain surrounding the notch. Each node is then assigned the appropriate restraints. The nodes on the left border of the notch are given displacements to represent the force from the nail or bolt. The nodes on the right border of the specimen are all treated as fixed connections, excluding the end one which is treated as a pin. All of the other nodes are free to move. The experimental tension test was performed by inserting a bolt through a drilled hole in the wood and then through a piece of steel with a comparable predrilled hole. Steel was used to ensure that the wood failed on the side of the connection that was being recorded. Strain gauges were then attached to measure the extension of the wood. For the nailed connections, a concrete nail was used to hold the wood and the steel together and prevent slippage. All of the 20 tests for each connection were recorded with digital microscopy. The comparative results of the computer simulation and the tension tests were very similar. The typical computer simulation of the nailed and bolted connection predicted a generally linear extension vs. load curves that was very similar to the curves created from the tension test data. The visual deformations of the meshes when