Rate-Dependent Cohesive Models for Dynamic Mode I Interfacial Propagation and Failure of Unidirectional Composite Laminates

With the increasing application of composite materials in anti-impact structure, the development of reliable rate-dependent interlaminar constitutive model becomes necessary. This study aims to assess and evaluate the applicability of three types of rate-dependent cohesive models (logarithmic, exponential and power) in numerical delamination simulation, through comparison with dynamic test results of double cantilever beam (DCB) specimens made from T700/MTM28-1 composite laminate. Crack propagation length history profiles are extracted to calibrate the numerical models. Crack propagation contours and fracture toughness data are predicted, extracted and compared to investigate the difference of the three different rate-dependent cohesive models. The variation of cohesive zone length and force profiles with the implemented models is also investigated. The results suggest that the crack propagation length can be better predicted by logarithmic and power models. Although crack propagation length profiles are well predicted, the numerical calculated dynamic fracture toughness tends to be higher than that of experimental measured results. The three models also show differences in the prediction of maximum loading forces. The results of this work provide useful guidance for the development of more efficient cohesive models and more reliable interface failure simulation of impact problems.

Engineering Advice for Preventing Crack on the Upstream Surface of Super-High Arch Dam

In this paper, the crack stability and crack propagation regularity of the upstream surface of super-high arch dam along the water-stop structure were analyzed in the framework of fracture mechanics. According to fracture toughness of dam concrete, the relationship between the crack propagation length and the allowable water pressure was studied. Finally, two main specific engineering suggestions for avoiding this kind of crack on the upstream surface of super-high arch dam were given: (1) the value of checking water pressure should not exceed 0.4 MPa; (2) the flange of the water-stop structure near the upstream surface of dam should be changed toward the downstream.

Numerical Analysis on Roller Compacted Concrete under the Action of Pure Water Pressure

Based on the RCC（roller compacted concrete） gravity dam, considering the multiphase, heterogeneity and microscopic structure characteristics of RCC, we use the RFPA analysis system to analyze the whole destruction process of the RCC weak level under the action of the pure water pressure in this paper. By simulation, we obtained the distribution of the stress, elastic modulus, water pressure on the whole failure process of RCC weak level and several parameters, such as the up crack load, instability load and critical crack propagation length. By calculation, we got the double K fracture toughness of RCC under the different of water pressure, and the results show that the up crack toughness and instability toughness change regularly with the increasing of water pressure initial value in the mass.

Simulation of Reflective Crack Propagation Path in Asphalt Overlay under the Partial Wheel Load

Partial wheel load is one of the main causes that lead to shear-type reflective crack of asphalt overlay in the old cement concrete pavement. Based on the theory of fracture mechanics and finite element method, this paper focuses on the numerical simulation of the reflective crack propagation path in asphalt overlay under the partial wheel load. Calculation result and analysis show that reflective crack partially expands upwards at the side of wheel load under the effect of partial wheel load with a sequential increase of crack propagation length. As the crack propagation length increases, stress intensity factors grow rapidly in the early period, and then increase by degrees slowly and, in the later period, the amplitude grows increasingly. Stress and strain fields enhance as the reflective crack increases upwards and the crack propagation angle expands gradually with the increase of reflective crack propagation length.