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The dynamic mode-I energy release rate of cracks propagating along elastic interfaces in double cantilever beams under high loading rates is derived analytically for the first time by accounting for structural vibration, wave propagation, and the Doppler effect along with the assumption of crack tip energy conservation. The developed theory can be used to study the "stick-slip" crack propagation behavior commonly observed in experiments, a progression of crack initiation, propagation, arrest, and reinitiation. In addition, the developed theory can be applied to measure crack initiation toughness as well as crack arrest toughness. The developed theory is verified against results from finite-element-method simulations of two experimental cases under high loading rates, demonstrating the excellent ability of the developed theory in capturing the crack propagation behavior as well as the ability in assessing dynamic mode-I energy release rate. [ABSTRACT FROM AUTHOR]

A dynamic mode-I energy release rate (ERR) of a double cantilever beam (DCB) under impact from a striker is derived for the first time for isotropic and orthotropic composite materials, accounting for DCB properties, a striker mass and an initial impact velocity. This is achieved in the context of structural vibration analysis by employing beam dynamics. It is found that the initial impact velocity determines the magnitude of the ERR, which is proportional to the velocity squared, while the delamination length ratio and the mass ratio between the striker and the DCB defines the time response. To understand the transient effect, a dynamic factor is defined as a function of the mass ratio. This factor decreases with an increasing striker mass, indicating a transition in the dynamic response from flexural-wave dominant to quasi-static-motion dominant, allowing an attunable dynamic effect. The developed theory is verified against the finite-element simulations for isotropic and orthotropic materials as well as experimental verification using published data. This work allows the measurements of fracture toughness under the impact load with the derived analytical solution. In addition, the developed theory can guide a design of impact tests and provide a fundamental understanding of impact-induced fracture for carbon-fiber-reinforced plastics. [Display omitted] [ABSTRACT FROM AUTHOR]

• Analytical theory for dynamic energy release rate of a double cantilever beam. • Consideration of dynamics, including vibration, and dispersive wave propagation. • Stationary and propagating delamination under high loading rate are both considered. • Theory predicts dynamic energy release rate, and initiation, propagation and arrest. • Finite-element-method simulations and experimental results validate the theory. Analytical theory for the dynamic delamination behavior of a double cantilever beam (DCB) under high loading rate is developed. Structural vibration and wave dispersion are considered in the context of Euler-Bernoulli beam theory. The theory is developed for both initiation and propagation of delamination in mode I. Two solutions for the energy release rate (ERR) are given for a stationary delamination: an accurate one and a simplified one. The former is based on global energy balance, structural vibration and wave dispersion; the latter is 'local' since it is based on the crack-tip bending moment. For the simplified solution to be accurate, sufficient time is needed to allow the establishment of all the standing waves. For a propagating delamination, a solution for the ERR is derived using the same simplification with the crack-tip bending moment. The obtained ERR solutions are verified against experimental data and results from finite-element simulations, showing excellent agreement. One valuable application of the developed theory is to determine a material's dynamic loading-rate-dependent delamination toughness by providing the analytical theory to post-process test results of dynamic DCB delamination. [ABSTRACT FROM AUTHOR]

The double cantilever beam (DCB) tests are widely used to assess the interfacial delamination properties of laminated composites. For quasi-static loads, the DCB tests are standardized based on the beam mechanics; for dynamic loads, however, such as high-loading-rate impact and cyclic loads, there is no established analytical theory. This presents a significant obstacle preventing the research community from assessing the delamination behavior of composites or adhesives for their application under complex in-service loads. In this paper, the theory of evaluating dynamic mode-I delamination driving force for DCBs under general displacement loads is developed for the first time, accounting for structural vibration effects. The developed theory is demonstrated by two examples: high-loading-rate split Hopkinson bar impact and cyclic fatigue loads. The analytical solutions are validated by published experiment results and in-house tests. This work provides a fundamental analytical tool to study and assess the fracture behavior of fiber reinforced-polymer composite and adhesive materials under various loading conditions. [Display omitted] • Analytical theory developed for mode-I dynamic energy release rate. • Quasi-static, dynamic, and general cyclic loads solved analytically. • Structural vibration included to account for dynamic effect. • Dynamic effect studied and quantified with induced displacement. • Finite-element-method simulation and in-house fatigue test verify the analytical theory. [ABSTRACT FROM AUTHOR]

The theory of dynamic three-point bending tests under high-loading rates is developed for the first time with account for structural vibration. Analytical solutions for dynamic normal (flexural) and shear stresses are derived. To study the dynamic effect, dynamic factors for both types of stresses are defined and investigated by employing a dimensionless characteristic time and a strain rate. It is found that both dynamic factors attenuate with respect to the characteristic time and, therefore, the quasi-static time thresholds and loading conditions are obtained. In addition, the dominant failure mode is studied for potential application in brittle materials in terms of normal-to-shear stress ratio, which is oscillatory in contrast to the quasi-static case. The developed theory is verified with a split Hopkinson bar test together combined with digital image correlation as well as finite-element simulations. The findings of this study can provide a guideline for test design, such as selection of specimen geometry and loading rate. As the theory provides a modal decomposition of dynamic normal and shear stresses, it can also be used in the field of structural health monitoring. • Development of theory for dynamic three-point bending under high loading rates accounting for structural vibration. • Evolution of dynamic factors to derive classification of dynamic and quasi-static condition and loading rates. • Investigation of the dominant failure mode with respect to the normal-to-shear stress ratio. • Verification of the developed theory against Hopkinson bar test with digital image correlation method. [ABSTRACT FROM AUTHOR]