Factors influencing the measured adhesive strength between glass and encapsulant of photovoltaic modules

Peel tests are used in Photovoltaic (PV) industry to check the encapsulation quality of PV modules. The test results are influenced by variable factors including peel speed, peel angle, mechanical strength of both adhesive and adherend, as well as testing environment. This paper analyses the correlation of measured peel strength with several main factors of peel speed, peel angle and curing state of encapsulant. Laminates with a structure of Glass-Ethylene Vinyl Acetate (EVA) - double Polyethylene Terephthalate (PET/PET) are fabricated at variety conditions to achieve different curing states of EVA. Peel test between glass and EVA of these laminates are examined at the angle of 90o. Peel strength at different speeds and at angles of both 90o and 180o are also evaluated at fixed lamination condition. Finite Element Model (FEM) for 90o peel test is developed using Abaqus software. The interfacial fracture energy between Glass and EVA is calculated using Virtual Crack Closure Technique (VCCT). Results show that peel strength increases with the increasing peel speed and curing state. Fracture energy calculated from FEM modelling also indicates an increasing trend with peel speed.