Volume 11 (2011): Issue 2 (June 2011)

Titanium as well as carbon based biomaterials, seem to be good candidates for future blood-contact applications. Bio-materials such as: Ti, Ti+DLC, TiN; Ti(C, N) with higher carbon concentration and DLC (diamond like carbon) were under examinations. Trials on surface modification of PU (polyurethane) substrate using ion mill were performed. Materials were deposited as thin films by the hybrid pulsed laser deposition (PLD) technique to examine the influence of the fabricated surfaces on cell behavior. The metallic titanium as a target was used for titanium based-film and graphite one for DLC. Phase content of deposited films was controlled by the flowing gas mixture of Ar+N₂ and Ar+N₂+C₂H₂ type in the reactive chamber. Sputtering of graphite was carried out in Ar atmosphere. The kinetic energy of the evaporated particles was controlled by application of variation of different reactive and non reactive atmospheres during deposition. Transmission electron microscopy (TEM) was used to reveal structure dependence on specific atmosphere in the reactive chamber. The measurement of the strength of bonds between biomaterials and cells is a major challenge in cellular biology since it allows for the identification of different species in adhesion phenomena. The biomaterial examinations were performed in static conditions with Dictyostelium discoideum cells and then subjected to a dynamical test to observe the cell detachment kinetics. For a given cell, detachment occurs for critical stress values caused by the applied hydrodynamic pressure above a threshold which depends on cell size and physicochemical properties of the substrate, but it is not affected by depolymerization of the actin and tubulin cytoskeleton. Tests revealed differences in behavior in respect to the applied coating material. The strongest cell-biomaterial interaction was observed for the carbon-based materials compared to the titanium and titanium nitride.

A surface fuctionalization was realized by: (i) fabrication of migration channels by laser ablation, (ii) electrospinning and (iii) deposition of multilayer film from polyelectrolites. A goal of the performed research was formation of scaffolds for bio-mimetic coatings. Surface morphology examinations and biomedical studies on porous and semi-porous materials with application of human endothelial cells HUVEC line were performed by application of confocal laser scanning microscopy (CLSM).

Plasma spraying is most used thermal spray process for coating of bioceramic and bioinert materials. It is line of sight technique, easy to use and inexpensive as compared to other processes used for coatings. The main disadvantage of this technique for coating hydroxyapatite (HA) is that due to high temperature of plasma (of the order of 16000°C) HA tends to degrade into amorphous calcium phosphates. These amorphous phases are not desirable and have a tendency to dissolve in body environment. In this article an attempt has been made to understand the plasma spraying process for coating of hydroxyapatite.

Over the past twenty years, the increase of use of structural materials in Aerospace is due to many reasons. While the properties of metallic materials are mastered, the risk behavior of composite materials requires monitoring of the structure. That's why many methods of non-destructive testing (NDT) have been implemented and applied for the evaluation of defects in composites.

The purpose of our research is the development of a new NDT tool for detecting delamination damages in aircraft's structures. The principle diagnostic is based on the application of a reproducible impact wave on a composite panel and its propagation trough an accelerometer sensor network. The presence of defects will be identified by the temporal and frequency response change compared to calibrated reference recorded before the damage.

Therefore, in this paper an experimental study of impact behavior of a composite laminate structure will be presented. The panel is made from a guarded composite long carbon fiber laminate. In the study, the shock propagation wave induced in the materials will take into account the fiber orientation (0°, 45°, 90°, -45°) and plies arrangement (plies stacking sequence of tilt-up). First results of this new NDT for detecting damages of an aircraft structure composite demonstrate the wide possibilities of this technique.

This article describes recent refinement of the traditional wedge test technique used to characterize durability of the adhesive joints. We propose two types of measuring protocols to monitor precisely and continuously the propagation of an "effective" crack during long term mode I fracture mechanic test. First method is directly derived from the traditional wedge test technique and consist in monitoring the surface strain of adherent with resistive gauges. The second method consist in replacing constant applied displacement by constant force loading and monitoring the beam deflection. Applications of these techniques are presented concerning crack propagation and nucleation monitoring leading to better understanding of the phenomena occurring in the joint subjected to an external load.

The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated laths of ferrite into the retained austenite. The purpose of the present paper is to demonstrate how a thermodynamic method can be used for solving a problem of the decarburisation of bainite laths. This should in principle enable to examine the partitioning of carbon from supersaturated ferrite laths into adjacent austenite and the carbon content in retained austenite using analytical method. The obtained results illustrates that the estimated times with the reference to the executed thermal processing are not capable of decarburising the sheaf of ferrite included thick laths of bainitic ferrite during the period of austempering. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but it is a mixture of bainitic ferrite, retained austenite and carbides.