Presentation on theme: "Tensile Strength of Composites"— Presentation transcript:
1 Tensile Strength of Composites Santa Rosa Junior CollegeEngineering 45Fall 2011Tim Robbins, Nick Howard, Nick Johnson, Saul Estrella
2 An Introduction to Composites Composites are defined as any material containing two or more substances which significantly displays the properties of all constituent parts in order to create a whole with a better combination of properties.Picture of ski composite(Courtesy: Materials Science and Engineering:An Introduction, 7th Edition)
3 An Introduction to Composites Much of the time, composites are made of two materials:The matrix, which is the main and continuous material.The dispersed phase, which is suspending within the matrix and does not have to be continuous.There are three main categories of composite materials:Particle-reinforcedFiber-reinforcedStructural
4 Particle-reinforced Composites Particle-reinforced composites use small particulates as the dispersed phaseExample: concrete, where the cement is the matrix and the sand/gravel forms the dispersed phase(Courtesy: Materials Science and Engineering:An Introduction, 7th Edition)
5 Fiber-reinforced Composites Fiber-reinforced composites use fibers with large strength to weight ratios as the dispersed phaseExample: our samples containing carbon fiber fabric and fiberglass (dispersed phase) in an epoxy matrixDifferent possible fiber alignments(Courtesy: Materials Science and Engineering:An Introduction, 7th Edition)
6 Structure CompositesStructure composites are made of layers of materials that have direction specific strengthExample: skis, where layers of fiberglass are laminated together in order to give strength in more than one direction(Courtesy: Materials Science and Engineering:An Introduction, 7th Edition)
7 Applications of Fiber-reinforced Composites Aerospace components (wings, propellers, fuselages, etc.)BicyclesRacecarsHelmetsSurf BoardsBoeing 787 composite fuselage.(Courtesy: Leo Watson)
8 Our ExperimentObjective: The purpose of our experiment was to find the stress-strain profiles for composites made of combinations of epoxy, carbon fiber fabric, and fiberglass.Our intent was to compare the results from two composite samples with that of a third purely epoxy control sample.
9 Mold CreationWe used the TAP Silicone RTV Mold Making System. This system is composed of liquid silicone which is activated by a tin catalyst.After mixing the two parts of the molding material together, we slowly and carefully poured it over the sample.After about a week, the mold was completely cured.
10 Resin Resin choice: Polyester Epoxy Tap Plastics: 1 to 1 General Purpose Epoxy ResinIdeal for high strength applicationsMinimal Shrinkage (<1%)Published Properties: (Courtesy: TAP Plastics)Tensile Strength: 7,500 psiFlexural Strength: 11,500psiHardness: 95 Rockwell R
11 Samples We created three samples: Pure epoxy control Epoxy with S-2 woven fiberglassEpoxy with unidirectional carbon fiber fabric
12 TestingWe were unable to successfully test our samples in the tensile strength machine, so we instead did a three-point test.However, since we did not design our experiment around the three-point test, our results are largely qualitative.
13 Three-Point TestThe three-point test is done by placing the specimen across two supports and applying a compressive load in the middle.Due to our sample shape, the flexural strength is calculated according to the equation:(Courtesy: Materials Science and Engineering:An Introduction, 7th Edition)Ff = load at fracture pointL = distance between supportsR = radius of the specimen
14 Control Sample Measured: σfs= 3853 psi (the number for L is taken as ~3 in.)σfs= 11,500 psi(from TAP technical specifications)
15 Epoxy with Fiberglass Measured: σfs= 33015 psi (the number for L is taken as ~3 in.)
16 Epoxy with Carbon Fiber Fabric Measured: σfs= psi(the number for L is taken as ~3 in.)
17 Control Sample Image shows difference in thread sizes between control and carbonfiber sample after stretching control.
20 IssuesOur biggest issue was that our samples slipped out of the tensile machine due to not being completely cured.If we were to repeat this experiment, there are several things we could do to fix this problem:Apply heatNot test samples prematurelyDo a three-point test from the start
21 AcknowledgmentsDr. Younes Ataiiyan for all his guidance and advice, especially when things did not go according to plan.TAP Plastics for giving us student discounts and advice concerning material selections.
22 Works Cited Callister, William. Materials Science and Engineering: An Introduction. 7th ed. York, PA: John Wiley & Sons, Inc., 2007.TAP Plastics. TAP Plastics, Inc., Web. 13 Dec <http://www.tapplastics.com/>.Watson, Leo. Aviation Spectator. Aviation Spectator, Web. 13 Dec