Polymer and Metal Tensile Testing:
- Measure the cross-sectional are (thickness and width) of specimen by using a caliper
- Load the specimen to the equipment.
- Lower the specimen to the bottom clamp slowly and tighten it by the hand
- Clamp the specimen tightly by the upper clamp
- Activate the specimen protection
- Set all the readings to zero
- Execute the test
- Get the data, fill in the following table and plot the graph of Stress vs. Strain using Excel
- Remove the Specimen
- Finally compare all the three curves in one frame of axes and discuss about the differences.
- Why there are variations in the mechanical properties of material of the same type?
- Why differences exist in mechanical properties of different materials?
- What is the majority difference between polymer and metals in terms of mechanical behaviour?
(B) Scanning Electron Microscope (SEM)
- Vent the column and insert specimen
- Pump down (evacuate)
- Select accelerating voltage, spot size and working distance
- Turn on high voltage
- Select load current (3-5kv for polymers and 15kv for metals and ceramics)
- Turn up filament (touch the orange bar)
- Select TV rate
- Adjust the image and save.
- What do you think may be caused if there is too much moisture on the specimen?
- What is the working distance and accelerate voltage if the specimen is titanium?
- Why can’t we heat the filament too fast?
(C) Composite Material Processing
- Take 5 pieces of the fiber matt.
- Weigh the fiber matt and record down the weight of the fiber matt used. In this case we will use 1:1 ratio between fibers and matrix; 5:3 ratio between epoxy and hardener solution.
- Arrange the plastic sheet, Teflon sheet and tissue paper in the following way.
- Calculate the weight of epoxy required (62.5% x weight of the fiber matt) and record down in the logsheet.
- Calculate the weight of hardener solution required (37.5% x weight of the fiber matt) and record down in the logsheet.
- Pour and weigh the required amount epoxy into the plastic cup.
- Pour and weigh the required amount hardener solution into the plastic cup.
- Stir and mix the solution with ice cream stick for 2-3 minutes.
- Put the first fiber matt on the Teflon sheet.
- Pour small amount of the solution and spread over the fiber surface.
- Quickly put the second fiber matt on top of the first fiber matt.
- Pour some of the solution on and spread over the fiber surface.
- Repeat step number 11-12 for all the five fiber matt.
- Quickly cover the fiber matt with Teflon sheet, tissue paper and the plastic sheet as shown in the arrangement in step number 3.
- Put on some weight and leave it for 1-2 hours.