A Highly Controllable and Large-Stroke Split High-Speed Tensile Testing Machine for Soft Materials at Intermediate Strain Rates

Background: The dynamic mechanical behavior of soft materials is critical for the study of impact injury of biological tissues, and the development of tissue simulants and soft armors. However, the conventional collision-driven apparatuses are hard to measure the stress–strain curves of soft materials at intermediate strain rates steadily. Objective: This study aims at developing a tensile testing machine that achieves large deformation of soft materials with adjustable and steady velocity, and diminish the disturbance of vibration under high-speed loading. Methods: A split high-speed tensile testing machine (SHTTM) is designed, which mainly consists of two split components: one platform with a force sensor and a fixed gripper, and the other one integrating a mobile gripper and a collision-based driving component driven by a linear motor. Data acquisition devices and high-speed camera are used to record the force and strain field of the specimen. Results: The apparatus could conduct tensile test on soft materials at a constant speed up to 5 m/s with the stroke of 0.7 m. The stress–strain curves of soft materials with different moduli are obtained considering the conditions of uniaxial deformation, constant strain rate and stress equilibrium. Conclusions: This apparatus provides an innovative approach to study the dynamic response of soft materials within the range of 1–100 s⁻¹, with the merits of constant speed, large stroke and high signal-to-noise ratio. It enables the study of the rate-dependent mechanism of ubiquitous natural and synthetic soft materials and the development of strain-rate-adaptive soft protective systems.