Test Fixtures for ASTM C158 Model: G-ASTM-C158

Flexural Testing of Glass (Modulus of Rupture). Glass is a unique challenge because its strength is a function of time and environment (static fatigue). This standard requires a specific stress rate (typically 1.1 MPa/s) rather than a constant crosshead speed. MTO’s Load Rate Control algorithm is essential here; it adjusts the crosshead velocity in real-time to maintain a constant increase in fiber stress on the specimen’s tension face. Furthermore, because glass is highly sensitive to contact stresses, our C158 fixtures utilize rubber-coated or high-polish rollers to prevent surface bruising at the load points. For customers in the automotive or architectural glass sectors, we emphasize the use of our environmental chambers, as moisture levels can significantly alter the crack propagation velocity at the microscopic level during the test.