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This study aims to investigate a finite element analysis on Al/CFRP Hybrid composites with a flaw in-between bonding surfaces. 2D model was considered to simplify the 4-layered structures with a circular flaw. The determination of debonding condition on multi-layered hybrid composites is subtle because the crack paths are unpredictable. In this model, the crack profiles depend on the applied stress, materials, bonding strengths and initial shapes of the flaw. The main idea is to find the key reason of failure on this material by means of fracture mechanics approach. The crack opening profiles are interesting to determine what kinds of factors are more influential for the structure. Williams expansion was used to analyze the profiles by the simulation results. We finally take into account the results to discuss the main fracture mechanism with the influential factors.

This work investigates the fabrication of microholes in carbon-fiber-reinforced polymer (CFRP) composite by powder-mixed microelectrical discharge drilling (PM$\mu$EDD) method. Initially, pilot experiments were carried out to understand the effect of powder concentration on the machining time and material removal mechanism. Then the full-factorial experimental analysis was performed to investigate the micromachining performance of CFRP composite. The input factors considered for the full-factorial analysis were powder concentration (2, 4, and 6 g/L), capacitance (100, 1000, and 10,000 $\mu$F), and tool rotation (300, 400, and 500 rpm). The regression analysis was carried out to assess the significance of the chosen input factors. The surface morphology of the fabricated microhole was extensively studied to establish the material removal mechanism and failure mechanisms of the composite constituents.

The use of fiber-reinforced polymer (FRP) has been widely recognized to be an effective and economical way to strengthen existing structures or repair damaged structures for extending their service life. This study investigates the feasibility of using nonlinear guided wave to monitor crack-induced debonding in FRP-strengthened metallic plates. The study focusses on investigating the nonlinear guided wave interaction with the crack-induced debonding. A three-dimensional (3D) finite element (FE) model is developed to simulate the crack-induced debonding in the FRP-strengthened metallic plates. The performance of using fundamental symmetric ($S_0)$ and anti-symmetric ($A_0)$ modes of guided wave as incident wave in the second harmonic generation at the crack-induced debonding is investigated in detail. It is found that the amplitude of the second harmonic and its variation with different damage sizes are very different when using $S_0$ and $A_0$ guided wave as the incident wave, respectively. The results suggest that it is possible to detect potential damage and distinguish its type based on the features of the generated second harmonic.

Realizing the importance of widely used technique of plating for flexural retrofitting of reinforced concrete (RC) beams and its drawbacks due to premature failure(s), present work concentrates in developing a finite element tool model capable of successfully capturing multiple premature failure modes and their corresponding behaviors. The model is simple but focused; the capability and accuracy of the results have been validated through test literature, particularly focusing on the load capacities of beams at progressive stages of failure modes; which is from crack initiation through to complete failure, such as the load of crack initiation, first crack and complete failure. Acceptable accuracy is shown in terms of crack type(s), crack patterns, sequence, location and direction of propagation through the innovative use of cohesive zone model (CZM). The model clearly explains that debonding and peeling, although originating from a same location for most cases, are extensions of different types of cracks.

A restriction of the use of lead in electronics can be expected. Conductive adhesives are able to replace the lead containing solder. The alternative joining technology should not only replace lead, debonding of the connection must be possible for the purpose of repair and recycling, too. Possible methods for debonding are described as well as requirements of environmentally friendly adhesively bonded electronics.

In this work, a recently proposed numerical tool is used to predict the onset and growth of debonds appearing along a single glass/carbon fiber embedded in an epoxy matrix subjected to transverse loads. The fiber-matrix system is modelled using the FEA commercial code ABAQUS, together with a solving algorithm programmed in Python and named Sequential Linear Analysis (SLA). Besides, the interface behavior is modeled using the Linear Elastic Brittle Interface Model (LEBIM) included in ABAQUS by means of a UMAT subroutine. The developed models are able to reproduce the non-symmetrical (one-side) debond at the fiber-matrix interface. Moreover, the results obtained show that the appearance of a unilateral debond may be affected both by the material employed and the size of the matrix cell where the fiber is embedded.

Cortical bone consists of osteons embedded in interstitial bone tissue and there is a thin amorphous interface, named cement line, between osteon and interstitial bone. Due to fatigue and cyclic loading, the pullout or debonding phenomenon often occurs in osteonal and interstitial tissue bone. The study aims to construct a fiber-reinforced composite material debonding model for cortical bone, in which the bonding condition along the osteon, cement line and interstitial tissue bone are assumed to be imperfect. In the study, we used the complex variable method to obtain series representations for stress fields in the osteon, cement line and the interstitial tissue bone with a radial crack. The effects of material properties of osteon and cement line, crack position, and varying degrees of debonding on the fracture behavior were investigated by computing the stress intensity factor (SIF) in the vicinity of the microcrack tips. The investigation results indicated that the cement line was important for controlling the fracture toughening mechanisms and that the level of imperfect bonding among osteon, cement line and interstitial tissue bone had a pronounced effect on the crack behavior and should not be ignored.

This paper investigates on the transient behavior of debonded composite pretwisted rotating shallow conical shells which could be idealized as turbine blades subjected to low velocity normal impact using finite-element method. Lagrange's equation of motion is used to derive the dynamic equilibrium equation and the moderate rotational speeds are considered neglecting the Coriolis effect. An eight-noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the impact parameters. The time-dependent equations are solved by using Newmark's time integration scheme. Parametric studies are performed to investigate the effects of triggering parameters like angle of twist, rotational speed, laminate configuration and location of debonding considering low velocity normal impact at the center of eight-layered graphite-epoxy composite cantilevered conical shells with bending stiff , torsion stiff ([45°/-45°/-45°/45°]s) and cross-ply ([0°/90°/0°/90°]s) laminate configurations.

Based on the plate theory, a high-order nonlinear FEM model is developed for the coupling of shear/flexure with in-plane deformation of the RC slab strengthened with FRP. In this model, a special plate layer element is built, Darwin-Pecknold Constitutive Model is chosen by modification .Using the FEM model, the carrying capacity of FRP reinforced two-way RC slab is analyzed, the stress distributions of glue layer are obtained and the numerical results are in good agreement with the experimental data. Calculated results show that carrying capacity of FRP reinforced RC slab is about 114% higher than that of un-strengthened RC slab and concrete failure accounts for the disruption of RC slab strengthened with FRP. In addition, the effects of thickness of FRP strip on carrying capacity are discussed.