Papers by Keyword: Blister Test

Abstract: The blister test is a promising test method to determine the interface fracture toughness of thin films adhering to rigid fibre reinforced plastics. In this paper nonlinear finite element analysis is used to determine a suitable layout for both the shaft loaded and the pressurised blister test. On the example of a PET film adhering to a quasi-isotropic fibre reinforced plastic, it is shown that energy release rates in a range of 0-1500N/m can be obtained for a 0.5mm thick film if test parameters are carefully selected. The two main causes for deviations of the analytic solution from the FEA results is attributed to infringement of the membrane limit condition and plastic deformation in the film.

Abstract: Large advancements have been achieved in understanding nucleation and growth of CVD diamond, but adhesion of diamond film to substrates is poor and there is no good methods about how to quantitative evaluation of the adhesive strength. The blister test is a method appropriate for measuring the adhesion of CVD diamond. In this test a pressure difference is applied across a thin film and the pressure when the film separates from substrate is measured, and the adhesive strength of diamond thin film was calculated using analytical model. Using the finite element model, the deflection at the center of a free-standing window sample of diamond thin films is calculated as a function of applied pressure and the adhesive strength is obtained using the FEM. The result indicates that finite element method-based prediction of the total energy release rate is in good agreement with that obtained from analytical expressions and experimentally observed values.

Abstract: Adhesion properties of diamond thin films are essential to their performance in technical applications. To obtain the adhesive strength precisely and quantitatively has been the frontier issue to the related scientists and engineers. In this paper, a new experimental equipment for blister tests was designed purposely and fabricated considering related influencing facts. A free-standing window of diamond thin film with the support of silicon wafer was obtained by the aid of photolithography and anisotropic wet etching technology so as to improve the precision of quantitative adhesion measures of diamond films. The mechanics for calculating the quantitative driving force of blister-induced delamination of diamond thin film is presented, which is on base of intensive modeling and simulation. The laser interferometer measurement with fine solution was used to pick up dynamic signals of diamond thin film bulge deformation in micrometer scale and the relationship demonstration of stress to strain of the diamond thin film was available, as a consequence, the adhesive strength could be obtained precisely and quantitatively by the valid model. The paper confirms the accessibility to precise quantitative adhesion measures of diamond films and the results will be beneficial to wide application of diamond thin films in the related fields.

Abstract: In order to measure the mechanical properties of gold films on silicon substrate, two types of specimens, i.e., bridged films and circular membranes, are manufactured. Using a wedge tip, the bridged gold films are indented so that the films are pushed off, which is called as V-peel test. The load-deflection curves obtained by the V-peel test are analyzed with the concept of geometrically nonlinear beam by using the minimum potential energy theory together with Ritz method. Thus, Young’s modulus and residual stress of the bridged gold films are obtained. Blister test is also conducted to measure the Young’s modulus and residual stress of a circular gold membrane, of which deformation is measured by Twyman-Green interferometer. By gradually increasing the external pressure applied on the membrane, the interfacial fracture toughness between the gold membrane and silicon substrate is measured based on the concepts of interfacial fracture mechanics.

Abstract: Adhesion energy values for thermal oxide scales cyclically grown at 850 and 950°C in air on ferritic and austenitic stainless steels were obtained using an inverted blister test and a tensile test working in the SEM chamber. The blister test used water pressure for debonding the metalscale interface, whereas the tensile test led to transverse compression generating scale spallation by buckling. Adhesion energy, defined by energy for interface crack propagation by unit area, was shown to be in the range 10 to 650 J.m–2 for the chromia-rich scales with thickness in the micrometer range. Ferritic grades gave less adherent scales than austenitic ones, and a great influence of titanium was evidenced, greatly increasing scale adhesion; niobium was less operative. Adhesion was well connected with nature and morphology of Ti and/or Nb-containing precipitates at the metal-scale interface.