2016 – Various – Employing Knitted-Fabric Composites for Bridge Construction – Team 8
About the Project
The “Bridge in a Backpack” system, developed at the University of Maine’s Advanced Structures and Composites Center (ASCC), is currently constructed using Concrete Filled Fiber-reinforced polymer (FRP) Tubes (CFFTs) made with braided fabrics. This project aims to investigate the potential for using a knitted reinforcing fabric in the CFFTs. It is unknown what the outcome of using knitted fabrics will be, but possible benefits include changes to the strength of CFFTs, stiffness of CFFTs, ability to manufacture FRP sleeves with non-constant cross sections, and the ability to manufacture FRP sleeves having a shape that is similar to the desired final shape, thus reducing residual stresses due to shaping of the FRP sleeves.
This project propose is to investigate if it is possible to knit carbon fiber yarn, and to investigate the potential of knitted reinforcing fabrics by manufacturing and characterizing properties of braided and knitted coupons. Specifically, we will be following the ASTM D30/39 standard Test Method for Tensile Properties of Polymer Matrix Composite Materials. The estimated completion date is May 2016.
Weekly Updates
Week of October 4th, 2015
Our group had our kickoff meeting with our project supervisor, David Erb. Mr. Erb is the Senior R&D Program manager at the Advanced Structures and Composites Center here on campus and will be our main point of contact throughout this project. The meeting with Mr. Erb helped us to plan out what the deliverables should be by the end of each semester and the scope of the project.
Week of October 11th, 2015
The focus for this week has been on researching different types of composites that could potentially be used for this project. The research consisted of figuring out differences between braided fabrics and knitted fabrics, different types and styles of knitting, structure of a knit, and general behavior of a knitted composite.
Week of October 18th, 2015
No knowledge is useless knowledge. The objective this week was to get as many literature reviews done on as many relevant articles as we can. David Erb suggested that we look at Dr. Habib Dagher’s articles that he wrote about the “Bridge in a Backpack” system. Dr. Dagher’s article is very relevant and has given us a greater understanding as to what we need to know as we continue with this project.
Week of October 25th, 2015
This week we have been working on our interim report which is a mid-semester report where we describe all that we have done so far this semester. Our main focus was nailing down our literature reviews and making sure our Gantt chart was set up correctly so we know what needs to be done in a timely fashion for the rest of the year.
Week of November 1st, 2015
More research was done on resins, fibers, concrete, and composites to further prepare ourselves for our second meeting with Mr. Erb. Different components were assigned to each member such as fibers, concrete, composites, and resins. We also got a chance to look at the FAK knitting machine. Below is the a picture of main operating board. This where the power is turned on and the speed of the drum is controlled. It has two indication lights on it. One lets the user know there is power to the machine and the other indicates the machine has lost tension, the yarn broke, too much tension, or another safety feature has been broken.
Week of November 8th, 2015
Our group this week did research on the FAK or Fiber Analysis Knitter machine because there are some parts that need to be replaced in the machine. Once the parts are delivered to the ASCC we would like to get our hands on the machine to fix and adjust the machine to have it running smoothly by the time we need to knit some tubes and test them.
Week of November 15th, 2015
This week our group had our second meeting with David Erb where we discussed where we were in terms of research and basic understanding of knitted and braided composites. We developed what the scope of the project is and what deliverables Mr. Erb wants from us. Mr. Erb gave us some contacts where we could potentially buy knitted fabrics and yarns to use when the machine is up and running.
Week of November 22nd, 2015
We were donated some free samples of light carbon and light E-glass sleevings. A&P Technologies were kind enough to donate some of their sleevings to us so we can infuse and test the braided fabrics. We also looked into more companies such as Zoltech to find specific yarns that we could potentially use whether it be carbon fiber, Kevlar or another type.
Week of November 29th, 2015
The Advanced Structures and Composites Center requires safety training before anyone is allowed to work there. We did a safety training meeting at the ASCC, and several online safety questionnaires. We all successfully obtained our safety certifications. This allows us to access the building during normal work hours. This is great news as next semester we will be performing our testing and fine-tuning of the knitting machine.
Week of December 6th, 2015
The final week of the semester we finished our interim report, planned goals for the next semester, made a Gantt chart, and finalized paperwork to be able to work in the ASCC. We will keep in contact of over winter break, and discuss more what will need to get done over winter break to make sure we are still on track.
Week of December 27th, 2015
Carlton, James and Eric all met up over break to work on the knitting machine. They threaded the yarn through the machine and fixed the Tube Assembly on the Take-Up which takes up the slack of the knitted tube as it comes through the machine. Unfortunately, they were not able to get the knitting machine to start knitting properly.
Week of January 17th, 2016
We have been working actively to try to find yarns to be able to fabricate our tubes. We have successfully found 272 Denier (D) E-glass yarn from PPG Fiber Glass. They have generously donated us 15,000 yards of yarn. Below is a picture of the E-glass yarn called a bobbin.
At the same time we have been vigorously working on the knitting machine and reading the operation manual to understand the machine. We met with our adviser to discuss a game plan for the semester and to collaborate on working with him to fix the knitting machine.
Week of January 24th, 2016
There has been nonstop working on the knitting machine as it needs a lot of fixing. We fixed the Air-relay sensing arms and figured out how to operate them using the air to have them properly timed and operate correctly. We have added o-rings on the meterhead dials to control the skew roll. We then investigated how they worked, and adjusted them so we could adjust the timing of the yarn feed rate with the timing of the needles. We also fixed several needles on the current drum and deemed that there were several needles that were permanently broken and needed to be replaced. The low tab called the butt of the needle were broken off so they weren’t engaging.
This is a picture of the meterhead tower. This is the front view showing the three meterhead dials. The machine is capable of knitting three different yarns together.
Week of January 31st, 2016
Finally after a lot of adjusting we have a fairly good understanding on how to use the knitting machine. The final adjustments we made were adjusting the brush to open the needles and the finger guide. The brush finally opens are the needles right before they take the yarn. The finger guide now has enough clearance for the needles to not get jammed and guide the string into the needles without cutting the yarn or hitting the needles. The sinkers have been replaced and slide freely. We have got the machine knitting PVA yarn (Elmer’s Glue) flawlessly. This week we also finally got our E-glass yarn delivered.