Microbond fibre bundle pullout technique to evaluate the interfacial adhesion of polyethylene and polypropylene self reinforced composites

Self reinforced polymer composites possess a comparable shear and tensile strength unlike the glass or carbon fibre reinforced composites. Important deciding factors of overall efficiency of composite materials are the interfacial adhesion properties between the fibre and the matrix. Structural properties and processability of composite materials are also dependent on adhesion between the fibre and the matrix. Polypropylene and polyethylene self-reinforced composites are the systems investigated here for the purpose of analyzing the interfacial properties of these systems. Multiple fibre pullout test is an alternate method for single fibre pullout test with added advantages of more reliable statistically averaged data with less standard deviation and minimized chances for fibre breakage during testing. This test can also be verified for various volume fractions unlike single fibre pullout test. Micro bonds of matrix materials are cured on a bundle of fibres and by using a micro vise as an additional fixture, the interfacial strength and other interfacial properties are evaluated through fibre pullout. Surface tension between the fibre and the matrix plays an important role in this test. Thus from the contact angle and the frictional properties of the interface, the interface properties are evaluated. Interface properties obtained from this meso-mechanical semi empirical method are also compared with the properties evaluated from micromechanical formulations. Spectroscopic studies revealed the bonding characteristics during the interface formation and after failure. Fractography reveals the cause and nature of failure and substantiate the analysis.