End-friction effects on compressive fracture of fused silica glass: A novel double-cylinder test

Accurate determination of the intrinsic compressive strength of glass is crucial for protective engineering, yet conventional tests often overestimate this property due to radial constraints induced by end friction. This study establishes a reliable methodology for determining the intrinsic compressive strength of brittle glass materials. An innovative double-cylinder (DC) specimen configuration is introduced, effectively eliminating end-friction effects and enabling measurements under nearly ideal uniaxial stress conditions. Through systematic quasi-static and dynamic uniaxial compression experiments, the contributions of contact friction and material inertia are successfully decoupled. The results demonstrate a quasi-static strength of 2.24 GPa for DC, approximately 10% lower than that of conventional single-cylinder (SC) specimens, directly quantifying the constraint strengthening effect induced by end friction. Under dynamic loading at strain rates of approximately 750 s⁻¹, both DC and SC specimens exhibited strength increases of about 5%. High-speed imaging and numerical surface stress analysis revealed two distinct fracture modes: constrained shear fracture in SC specimens with cracks initiating at contact surfaces, and free tensile fracture in DC specimens with cracks originating at the glass-glass interface. These findings clarify the influence of end friction in compression testing and provide a reliable approach for evaluating the true compressive strength of brittle glasses in engineering applications.