Fracture Mechanics and Testing of Interface Adhesion Strength in Multilayered Structures – Application in Advanced Solar PV Materials and Technology

Abstract

Quantitative characterization techniques based on fracture mechanics were proposed and used to examine the interface strength in multilayered structures. Novel in situ micro-fracture testing for nanolayers inside a Scanning Electron Microscope (SEM) is developed to observe fracture evolution during bending deformation of nanolayered films. Other quantitative technique on interface fracture mechanics has been the 4-point bending or double cantilever beam bending methods. In this paper we will discuss about these two techniques and their applications. In particular, the Double Cantilever Beam bending test method using Delaminator v8.2 Adhesion testing system has been used to quantify the adhesion strength between the Solar PV backsheet and encapsulant. The environmental conditions in tropical countries makes the photovoltaics components vulnerable to salt mist and water vapour as well as acid penetration. Under moisture condition, the hydrolysis reaction of water vapour with backsheet materials release acetic acid, causing delamination and further corrosion of the encapsulant and inter-metallic connectors on solar cells by the salt mist leading to electrical shorts, heat accumulation and fire. Understanding the interface strength between these two materials and its degradation with typical environments in tropical and near-ocean regions is instrumental to enable robust and reliable solar PV technology for such regions.