BEHAVIOR OF UDM PROCESSED EPOXY BASED TiO2 NANO FILLER COMPOSITE ADHESIVE JOINTS UNDER FATIGUE LOADING

Abstract

In this investigation, the work has been carried out for determining the fatigue life cycles of single lap shear adhesive joint of Ultrasonic Dual Mixing (UDM) processed epoxy based TiO2 nano filler composite and neat epoxy. Bond line thickness of the adhesive joints was maintained to 300 μm with the help of placing wire of 150 μm diameter in between adherents. Adherent surface were prepared by sand blasting and then cleaning with acetone prior to bonding. Average and maximum surface roughness of adherents was found to be 3 μm and 22 μm respectively. Static tests have been carried out to find the ultimate lap shear strength of neat and composite epoxy adhesive. Ultimate lap shear strength of neat and composite epoxy adhesive joints was found to be 14.09 MPa and 15.02 MPa respectively. For fatigue tests stress ratio was taken to be 0.1 and tests were carried at frequency of 17.5 Hz at Stress levels (80, 70, 60, 55, 50, 40%) of ultimate tensile lap shear strength of adhesive joints. There was a considerable increase in the fatigue life cycles of the composite epoxy as compared to neat epoxy. Fatigue limit of neat epoxy joint was 40 % of UTLSS, while for composite epoxy joints it was 50% of UTLSS. Finite element mathematical model was made in ANSYS for determining the local stresses and stress distribution inside the adhesive layer. Crack initiation and propagation behavior was explained with the help of mathematical model. Homogeneous distribution of TiO2 nano particles in epoxy matrix was seen under FESEM. Composite epoxy adhesive joints went under adhesive failure, while neat epoxy adhesive joints went under both adhesive and cohesive failure.