Measurement of Interfacial Fracture Toughness Under Combined Mechanical and Thermal Stresses

1998 ◽  
Vol 120 (4) ◽  
pp. 349-353 ◽  
Author(s):  
J. Jiao ◽  
C. K. Gurumurthy ◽  
E. J. Kramer ◽  
Y. Sha ◽  
C. Y. Hui ◽  
...  
Keyword(s):  
Strain Energy ◽  
Thermal Stresses ◽  
Strain Energy Release Rate ◽  
Double Cantilever Beam ◽  
Strain Energy Release ◽  
Interfacial Fracture ◽  
Polyimide Film ◽  
Interfacial Fracture Toughness ◽  
Interfacial Fracture Energy ◽  
Beam Technique

The interfacial fracture resistance of a polyimide passivation/underfill interface was measured using an asymmetric double cantilever beam technique. A thin layer of polyimide was coated on a standard epoxy as one of the beams and an underfill was flowed over the polyimide film and cured to form the second beam. The relative contributions of the thermal and mechanical stress were systematically varied by varying the thickness ratio of the two beams. The results indicate that the effect of thermal residual stress must be taken into account in the calculation of critical strain energy release rate to obtain the interfacial fracture energy.

Continuous Microindentation and Microscratch Measurements of Metal-Ceramic Adhesive strengths

1991 ◽  
Vol 239 ◽  
Author(s):  
S. Venkataraman ◽  
D. L. Kohlstedt ◽  
W. W. Gerberich
Keyword(s):  
Fracture Toughness ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Interfacial Fracture ◽  
Interfacial Shear ◽  
Work Of Adhesion ◽  
Interfacial Fracture Toughness ◽  
Heat Treated ◽  
Metal Ceramic

ABSTRACTTo investigate the effect of heat-treatment on the adhesion of Pt thin films to NiO substrates, the strain energy release rate, interfacial fracture toughness and interfacial shear strength were determined from continuous microscratch and continuous microindentation experiments. Samples were prepared by sputtering Pt onto single crystals of NiO, followed by a heat-treatment at temperatures of 300, 500 and 800°C and an oxygen partial pressure of either 0.21 or 10-5 atm. Continuous microscratch tests were performed by driving a conical indenter with either a 1 or 5 μm tip radius simultaneously into and across the Pt film. From the magnitude of the critical load at the point of film delamination and the area of the delaminated piece of the thin film, the strain energy release rate (practical work of adhesion) and interfacial fracture toughness were calculated. The practical work of adhesion and interfacial fracture toughness increased from 0.2 J/m2 and 0.2 MPa√m, respectively, for as-sputtered samples to 4.6 J/m2 and 1 MPa√m for samples heat-treated at 500°C and 10-5 atm. Preliminary analysis of continuous microindentation results for Pt/NiO samples yielded interfacial shear strengths of 270 MPa for as-sputtered samples and 725 MPa for samples heat-treated at 500°C and 10-5 atm. While these values are in good agreement with those determined by other methods for metal-ceramic systems, there are sufficient differences in test method for a single system to require additional analysis of the proposed models.

scholarly journals Interlaminar Fatigue Crack Propagation in Mode I of Carbon Fiber/PEEK Composites

1993 ◽  
Vol 2 (1) ◽  
pp. 096369359300200
Author(s):  
G C Christopoulos ◽  
S A Paipetis
Keyword(s):  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Double Cantilever Beam ◽  
Cyclic Strain ◽  
Strain Energy Release ◽  
Mode I ◽  
Interlaminar Fracture Toughness ◽  
Fatigue Cycle ◽  
Delamination Growth ◽  
Thermoplastic Matrix

A study of the mode I interlaminar fracture toughness of a unidirectional carbon fibre reinforced thermoplastic matrix composite has been made using Double Cantilever Beam, DCB, specimens. Delamination growth per fatigue cycle, da/dN, was related with the maximum applied cyclic strain energy release rate, GIMAX, using a power law.

scholarly journals Computation of mode I strain energy release rate of symmetrical and asymmetrical sandwich structures using mixed finite element

2021 ◽  
Vol 15 (56) ◽  
pp. 229-239
Author(s):  
Amina Mohamed Ben Ali ◽  
Salah Bouziane ◽  
Hamoudi Bouzerd
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Double Cantilever Beam ◽  
Mixed Finite Element ◽  
Strain Energy Release ◽  
Mode I

The use of composite materials is on the rise in different engineering fields, the main advantage of these materials for the aerospace industry is their low weight for excellent mechanical qualities. The analysis of failure modes, such as delamination, of these materials has received great attention from researchers. This paper proposes a method to evaluate the mode I Strain Energy Release Rate (SERR) of sandwich structures. This method associated a two-dimensional mixed finite element with virtual crack extension technique for the analysis of interfacial delamination of sandwich beams. A symmetrical Double Cantilever Beam (DCB) and asymmetrical Double Cantilever Beam (UDCB) have been analyzed in this study.  The comparison of the results obtained by this method and those found in the literature shows efficiency and good precision for the calculation of Strain Energy Release Rate (SERR).

Adhesion of Thermal Barrier Coating Systems and Incorporation of an Oxidation Barrier Layer

1996 ◽  
Author(s):  
Y.C. Tsui ◽  
T.W. Clyne
Keyword(s):  
Residual Stress ◽  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Interfacial Fracture ◽  
Thermal Barrier ◽  
Stress Distributions ◽  
Barrier Coating

Abstract The adhesion of various interfaces in thermal barrier coating systems strongly affects their stability and thermal cycling life. A new spontaneous debonding technique and the four point bend delamination test have been applied to measure the interfacial fracture toughnesses of various interfaces in several thermal barrier coating systems. The spontaneous debonding technique is based on spraying a relatively stiff layer on top of the ZrO2 coating. This raises the strain energy release rate for debonding, the magnitude of which is monitored via modelling of the stress distribution. The critical strain energy release rate for debonding (interfacial fracture energy) was then determined from the stress states before and after debonding. Thermal barrier coatings (TBCs), consisting of a Ni-22wt.%Cr-10wt.%Al-lwt.%Y bond coat and a ZrO2-8%Y2O3 top coat, were deposited on a nickelbased superalloy. Two methods, air (APS) and vacuum (VPS) plasma spraying, were used to produce the bond and the top coats. The corresponding as-sprayed residual stress distributions and the interfacial fracture energies were evaluated. It was found that a VPS bond coat and an APS top coat produced the most mechanically stable structure. A layer of vacuum plasma sprayed AI2O3 was then introduced between the top and the bond coat, designed to act as an oxygen diffusion barrier. The effect on residual stress distributions, and associated crack driving forces for debonding, at different interfaces were determined. The effect of the alumina layer on the oxidation behaviour was also studied. It is shown that the oxidation barrier could significantly enhance the coating life-time.

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