Abstract The paper deals with the identification of the delamination in composites on the basis of the information for the displacements from the surfaces of damaged bodies. The identification of the active delamination region on the interface between two layers of given composite material is a non-linear programming problem that consists of minimization of a Kohn-Vogelius type of functional [3...

A recent variational mechanics analysis of microcracking damage in cross-ply laminates of the form [(S)/90n]s, where (S) is any orthotropic sublaminate much stiffer than [90n], has been extended to account for the presence of delaminations emanating from the tips of microcracks in the [902n]T sublaminate. The new two-dimensional stress analysis is used to calculate the total strain energy, effe...

Layered borosilicate zeolite precursor ERB-1P (Si/B = 11) is delaminated via isomorphous substitution of Al for B using a simple aqueous Al(NO3)3 treatment. Characterization by PXRD shows loss of long-range order, and TEM demonstrates transformation of rectilinear layers in the precursor to single and curved layers in the delaminated material. N2 physisorption and base titration confirm the exp...

Effect of elastic anisotropy on indentation-induced thin film interfacial delamination, especially, at the initiation and early growth stage, is examined. The indentation load is modeled as a constant pressure over an expanding semi-spherical cavity. The delamination process is approached by a cohesive zone model. The rest of the problem is formulated within the general anisotropic elasticity t...

Fiber reinforced polymeric composites can be employed for the construction of structures that are highly durable and easy to fabricate. At EMPA, a prototype footbridge with girders and deck made of pultruded composite sections has been designed and constructed. For thin-wall pultruded sections such as I-beam or T-beam, delaminations can form easily at the web/flange junction. If the delaminatio...

Impact tests were carried out on composite laminates and composite scarf repairs, while both were subjected to in-plane loading with tensile pre-strain levels up to 5000 microstrain. The results show that pre-straining of the composite laminates has no noticeable influence on the size of the delamination area for the given impact energy of 8 J, which represents a typical barely-visible impact o...

In the present research, the effects of delamination size and location on vibration characteristics of laminated composite beams are investigated both analytically and numerically. In the analytical method, the delaminated beam is modeled as four interconnected Euler–Bernoulli beams and the constrained and free mode models are both simulated. The differential stretching and the bending-extensio...

Polymers are used in biological micro-nanoelectromechanical systems BioMEMS/NEMS applications due to their desirable mechanical properties, biocompatibility, and reduced cost relative to silicon microfabrication processes. Understanding the interfacial properties of the films that are used in BioMEMS/NEMS serves as a useful tool in obtaining higher device yield and greater mechanical reliabilit...

In this paper we report on the mechanism of delamination in light-emitting diode (LED) packages and its effects on thermal characteristics of LEDs. The LED samples were subjected to moisture preconditioning treatments followed by heat block testing. Transient thermal measurements were performed for the investigation of the thermal behavior of the delaminated LEDs. Increase of thermal resistance...