Analysis of interlaminar stress and nonlinear dynamic response for composite laminated plates with interfacial damage

By considering the effect of interfacial damage and using the variation principle, three-dimensional nonlinear dynamic governing equations of the laminated plates with interfacial damage are derived based on the general sixdegrees-of-freedom plate theory towards the accurate stress analysis. The solutions of interlaminar stress and nonlinear dynamic response for a simply supported laminated plate with interfacial damage are obtained by using the finite difference method, and the results are validated by comparison with the solution of nonlinear finite element method. In numerical calculations, the effects of interfacial damage on the stress in the interface and the nonlinear dynamic response of laminated plates are discussed.

A STUDY OF THE INFLUENCE OF INTERFACIAL DAMAGE ON STRESS CONCENTRATIONS IN INTRAPLY HYBRID COMPOSITES

In the axial tensile failure process of intraply hybridcomposites, the breakage of some fibers may lead to interfacialdamage, thus directly influencing the local stress concentrationsnear the sites of breakage. A modified shear-lag model, in which theinterfacial damage is considered, is proposed. Based on the model,the influence of interfacial shear strength on the stressconcentrations and the lengths of interfacial damage zone is firststudied. The present results also provide an important theoreticalbasis for investigating the failure mechanism and hybrid effects forsuch kind of composites.

Interface bond degradation and damage characteristics of full-length grouted rock bolt in tunnels with high temperature

Full-length grouted bolts play a crucial role in geotechnical engineering thanks to their excellent stability.However,few studies have been concerned with the degrading performance of grouted rock bolts caused by extensive and continuous heat conduction from surrounding rocks in high-geothermal tunnels buried more than 100 m(temperature from 28C to 100C).To investigate the damage mechanism,we examined the time-varying behaviors of grouted rock bolts in both constant and variable temperature curing environments and their damage due to the coupling effects of high temperature and humidity through mechanical and micro-feature tests,including uniaxial compression test,pull-out test,computed tomography(CT)scans,X-ray diffraction(XRD)test,thermogravimetric analysis(TGA),etc.,and further analyzed the relationship between grout properties and anchorage capability.In order to facilitate a rapid assessment and control of the anchorage performance of anchors in different conditions,results of the interface bond degradation tests were correlated to environment parameters based on the damage model of interfacial bond stress proposed.Accordingly,a thermal hazard classification criterion for anchorage design in high-geothermal tunnels was suggested.Based on the reported results,although high temperature accelerated the early-stage hydration reaction of grouting materials,it affected the distribution and quantity of hydration products by inhibiting hydration degree,thus causing mechanical damage to the anchorage system.There was a significant positive correlation between the strength of the grouting material and the anchoring force.Influenced by the changes in grout properties,three failure patterns of rock bolts typically existed.Applying a hot-wet curing regime results in less reduction in anchorage force compared to the hot-dry curing conditions.The findings of this study would contribute to the design and investigations of grouted rock bolts in high-geothermal tunnels.

Nonlinear free vibration analysis of piezoelastic laminated plates with interface damage

This paper presents a nonlinear model for piezoelastic laminated plates with damage effect of the intra-layers and inter-laminar interfaces. Discontinuity of displacement and electric potential on the interfaces are depicted by three shape functions. By using the Hamilton variation principle, the three-dimensional nonlinear dynamic equations of piezoelastic laminated plates with damage effect are derived. Then, by using the Galerkin method, a mathematical solution is presented. In the numerical studies, effects of various factors on the natural frequencies and nonlinear amplitude-frequency response of the simply-supported peizoelastic laminated plates with interfacial imperfections are discussed. These factors include different damage models, thickness of the piezoelectric layer, side-to-thickness ratio, and length-to-width ratio.

NONLINEAR BUCKLING BEHAVIOR OF DAMAGED COMPOSITE SANDWICH PLATES CONSIDERING THE EFFECT OF TEMPERATURE-DEPENDENT THERMAL AND MECHANICAL PROPERTIES

On the basis of the first-order shear deformation plate theory andthe zig-zag deformation as- sumption, an incremental finite elementformulation for nonlinear buckling analysis of the composite sandwichplate is deduced and the temperature-dependent thermal and mechanicalproperties of composite is consid- ered. A finite element method forthermal or thermo-mechanical coupling nonlinear buckling analysis ofthe composite sandwich plate with an interfacial crack damage betweenface and core is also developed.