Bending Strength Test Method

The three-point bending test machine used on this page is not a commercial universal testing machine, but a simple device built by the site administrator. While the absolute accuracy is not high, it is expected to provide sufficient reproducibility for the purpose of "comparing test specimens fabricated under the same conditions."

The vertical control for applying load uses a stepping motor and lead shaft. The approximate displacement is controlled by calculating the lead shaft feed from the motor rotation angle.

The load is measured with a load cell rated at 100 kg. The signal from the load cell is read to record load changes during testing.

Most of the fixture body (base and holding parts) is 3D printed with PLA-CF, and the parts in contact with the test specimen (support point contact surfaces and center pusher) are fitted with SUS dowel pins with a diameter of φ10 mm. This prevents wear and deformation of plastic parts while providing the simplest possible contact conditions for the test specimen.

As described above, since this is a "DIY simple testing machine," the values obtained here do not fully comply with strict test standards. On this site, relative comparison when changing fabrication conditions or materials under the same fixture and conditions is the main purpose.

The bending strength test on this page is a simple evaluation for the purpose of "comparing test specimens fabricated under the same conditions." It is not a measurement that fully follows strict test standards in a dedicated test room, but is positioned as an experiment within the range possible in a home environment.

The external dimensions of the test specimen (thickness, width, etc.) are assumed to be as set during modeling, and dimensional measurements of individual test specimens are not performed before testing. Therefore, the values shown here should be treated as "comparison of bending strength when calculated based on design dimensions."

Regarding the test environment, it is not an environment where temperature and humidity can be controlled with dedicated equipment. Since testing is conducted in a home workspace, room temperature and humidity depend on the environment at the time. While extreme changes due to air conditioning or dehumidifier on/off are avoided, please note that this is not a strict environmental test.

Measurements are basically performed using three test specimens fabricated under the same conditions. The maximum load of each is recorded and treated as reference values for confirming trends.

Note that on this site, standard deviation and statistical variation evaluation are not performed. Also, detailed observation of fracture surfaces and classification of failure modes are not conducted, and data is published here for roughly comparing "which conditions/materials seem relatively stronger."