Introduction

You can find the material comparison tool here: material.nathantsoi.com.

There are many things to consider when choosing which type of 3D printer filament to use for a project. Considerations include the material's price, tensile strength, and ability to resist changes in temperature, moisture, or different types of chemicals.

While some manufacturers provide specifications that cover some of these considerations, I wanted to test the tensile strength and Young's Modulus of different engineering-grade materials under different conditions. In particular, PA6 nylon is particularly susceptible to moisture absorption during normal operation in the environment. Therefore, I built a tensile strength test rig and tested many materials. The results can be viewed at material.nathantsoi.com.

This article describes the testing methodology and the test rig I built to carry out the experiments:

Testing Methodology

My goals during testing were to make as fair a comparison between different materials as possible using a setup with a cost accessible to hobbyists. The cost of a typical universal testing machine starts at $10,000 and can go up to more than $150,000. My goal was to design a capable test rig that could be built for around $100.

The requirements for the test machine were defined by the test protocol.

Test coupon

The main factor that influences the cost of a typical universal testing machine is the amount of force the machine needs to exert on the test coupon. Therefore, I started by computing the force the machine would have to exert on the test coupons. Upon examining the ultimate tensile strength of the strongest materials I planned to test, I chose to use the ASTM D638 type V coupon, which has a cross-sectional area in the test section of 9.54mm^2, allowing breakage with under 200Kg of force.

For each material, I print 8 test coupons using the manufacturer's provided settings. In the case where a large temperature range is provided, I printed at the high end of the range for maximum layer adhesion. For maximum strength, the coupons are oriented so that the layer lines are parallel to the axis of the test.

Storage Protocol

Because we are concerned with the water absorption of the materials, I store four coupons in an air-tight container, with a pack of silica desiccant, from immediately after printing until the test is performed.

To test the filament's properties after water absorption in a humid condition, four more coupons are stored in a sealed container with 5 grams of water for 7 days. The water is added to simulate the conditions of a humid environment. These four coupons are then tested after 168 hours and the results are reported under the "wet" material property results.

Each reported result is the average of the 4 test episodes corresponding to the 4 coupons in the test.

Test Protocol

All materials were tested in the same environment at room temperature.

The following procedure is followed four times, once for each test coupon, for each material:

  1. The test coupon is loaded into the test rig clamps using a consistent clamping force.
  1. The test rig coupon and clamps are loaded into the test rig.

  1. The test rig is zeroed and data collection is begun.

  2. Until the coupon breaks, the test rig moves 200 steps in the positive direction and then measures the force exerted on the coupon via a load cell.

  3. The coupon breaks. Data collection is stopped and the test rig is stopped.