Study of Defect Coalescence in Heterogeneous Material Systems Using Broad Band Dielectric Spectroscopy

Abstract

Composite materials are essential for many modern applications, including airplanes and cars, energy conversion and storage devices, medical prosthetics, and civil structures. Detecting the initiation, growth, accumulation, and coalescence of micro-damage in these heterogeneous materials and predicting the onset of component failure using conformal Broadband Dielectric Spectroscopy (BbDS) is a promising area of ongoing research. Recently, the authors have developed the critical path concept and Heterogeneous fracture mechanics concept that depicts the effect of defect nucleation, growth, coalescence, and fracture plane development and correlation of these damage mechanisms to change in dielectric response respectively. Current research applies those concepts to detect the damage mode and the critical fracture path (conduction path) that leads to eventual failure. Also, the use of BBDS to detect the weak adhesion bonding is proposed, where the change in dielectric properties as a function of the frequency of the applied potential through the thickness of the sample is measured in the vicinity of the weak region. It is observed that at low frequency the gradient in the potential indicates a spike which marks the charge concentration around the imperfect region.

State Variable Methods of Assessment, Prognosis, and Control of Composite and Bonded Structures

“…We have observed over a wide range of composite materials and applied conditions (mechanical, thermal, electrical, chemical) that the through thickness dielectric response is directly and uniquely related to the internal microstructure and changes in local morphology [4,5,6]. More recently, Vadlamudi has succeeded in coupling ABAQUS predictive modeling of the development of microdamage (at the fibermatrix level) with COMSOL multiphysics modeling (by coupling those analyses) to predict the response to microdamage observed in Figure 3 (and in many other results obtained by the authors) [7,8]. An example of those results is shown in Figure 4.…”

(Invited) Towards the Physical Reliability of 3D-Integrated Systems: Broadband Dielectric Spectroscopic (BDS) Studies of Material Evolution and Reliability in Integrated Systems

“…The microwave-dielectric material interactions are reasonably granular and uniquely suitable for studying the buried structures and material interfaces inherent in integrated circuit devices. For example, such interactions can detect the weak adhesion bonding; a steep gradient of S-parameters at low frequencies indicates a charge concentration around the imperfect region 12 . Thus, in principle, detailed studies of broadband RF interaction with integrated circuit devices under stress should enable fast insitu detection of physico-chemical changes in the entire device such as defects, failure modes and mechanisms without the need for physical failure mode analysis (FMA).…”