Development of Modulus of Rupture Testing Machine for the Measurement of Flexural Strength of Brittle Materials

Ceramics and other brittle materials like glass, plastic, wood, and concrete beams or slabs are highly valuable both for domestic and industrial applications. Most of these brittle materials fail during transportation or use when minimal force is applied. It is wise to note that careless selection of these materials could lead to significant losses in both human and material resources. Meanwhile the modulus of rupture testing machine that can be used to measure the ability of these materials to withstand stress before failure are not readily available and at the same time very expensive in Nigeria. A machine is therefore developed to measure the modulus of rupture of brittle materials. The machine is developed using rigid metallic frame, 500 N load cell, HX711 load cell amplifier, 12 V dc motor, L298N motor driving module, arduino atmega 2560 board, 20x4 I2C liquid crystal display(LCD), MicroSD card module and infrared sensor. The frame provides structural support for other units of the machine, the loading system applies a controlled force on the material to be tested, the stage holds the specimen in place, and the data acquisition system records measurements. The machine is designed such that the loading head can be changed to carry out either three point bending (3-PB) test or four point bending (4-PB) test. The machine was successfully developed and calibrated. The calibration results demonstrated excellent measurement accuracy, with a maximum percentage error of only ±0.20%, indicating that the load cell and force measurement system provide reliable and precise load measurements over the operating range. The machine was used to measure the MoR of four tile samples. The values obtained when compared to those obtained experimentally were found to be very close with average percentage error of approximately 0.50%. The statistical analysis showed that the mean modulus of rupture measured by the developed machine (24.477 MPa) was very close to that obtained experimentally (24.351 MPa). The paired t-test carried out on the results indicated that there was no statistically significant difference between the two methods at the 97 % confidence level. This signifies that the machine can perfectly be used to determine the MoR of ceramic and other brittle materials.