Composites are more and more increasing their importance as one of the most interesting group of materials, because of their unique properties. Hole drilling operations are common in composite parts to facilitate fastener assembly. As composites are non-homogeneous this operation causes some damages like delamination and others that reduce bearing and fatigue strength of the composite part. A p...

Modeling generic size features of delamination, such as area or length, has long been considered in the literature for damage prognosis composites through specific models describing state evolution with load cycles time. However, delamination shape never considered, despite that it holds important information diagnosis and prognosis, including area, its center, perimeter, useful structural safe...

Whilst drilling is the most frequently employed operation of secondary machining for structure joining, delamination is a very serious defect during drilling of fiber-reinforced composite materials,. The evaluation of the delamination damage in the material is important but rather difficult, particularly for carbon fiber-based composites, because their colour makes visual inspection difficult. ...

Air – coupled ultrasonic investigation possess a great potential for investigation of aerospace composite materials, because it avoids disadvantages caused by immersion or contact techniques. In the work the test sample of the GLARE3-3/2 composite material with artificial delamination type defect was investigated. Numerical and experimental investigations using focussed air – coupled ultrasonic...

Thermal cycling tests are carried out under a temperature gradient using specimens of thermal barrier coating (TBC). Vertical cracks in the topcoat grow direction thickness, and transverse topcoat, which can lead to delamination, vicinity interface with bondcoat. At 1223 K at substrate surface, heat flux 1.39 MW/m2, remarkable growth is observed, whereas slower lower temperatures conditions. Th...

In this work, a comparative study on different drill point geometries and feed rate for composite laminates drilling is presented. For this goal, thrust force monitoring during drilling, hole wall roughness measurement and delamination extension assessment after drilling is accomplished. Delamination is evaluated using enhanced radiography combined with a dedicated computational platform that i...

A thermodynamically consistent damage model is proposed for the simulation of progressive delamination in composite materials under variable-mode ratio. The model is formulated in the context of Damage Mechanics. A novel constitutive equation is developed to model the initiation and propagation of delamination. A delamination initiation criterion is proposed to assure that the formulation can a...

A capacitor-based circuit model is proposed to explain the electrochemical delamination of two-dimensional materials from their native substrates where produced gas bubbles squeeze into the interface. The delamination is actually the electric breakdown of the capacitor formed between the solution and substrate. To facilitate the procedure, the backside of the ubstrate has to be shielded so that...

Ultrasonic guided waves are used to detect the delamination between skin and honeycomb of a composite helicopter rotor blade. Theoretical work is carried out for guided waves in the trailing edge of a rotor blade, which is a multilayer composite skin/NOMEX half space structure. The dispersion relation is obtained with the global matrix method. Theoretically driven experiments are conducted on a...

Using detailed finite element models, a fracture analysis of solder bumps and under bump metallurgy (UBM) in flip-chip packages is carried out. Our objective is to identify likely fracture modes and potential delamination sites at or near these microstructural components. In order to study flip-chips, whose dimension spans from sub-micron thickness UBM layers to several millimeters wide package...