Chevron notch testing of bonded polymeric interfaces

• Main Author: Lim, Terence.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/53440
• Institution: Nanyang Technological University

Thermoplastics are extremely attractive substrate materials for microfluidics systems, with the important benefits of producing of low-cost disposable devices for a wide range of bio-analytical applications. Many research activities have been directed towards the fabrication of microfluidic systems, and the bonding of thermoplastic layers is considered one of the most critical steps in fabrication. An ability to characterise the bond toughness is important for comparing the performance of alternative bonding techniques. Of the many bond testing techniques available, the chevron test is particularly appealing because the measurement of bond toughness occurs during stable propagation of an interfacial crack. Thus, a chevron test has been employed because it provides low scattering data and minimum plastic deformation under Mode I condition as compared to other bond toughness measurement techniques. Chevron test was used to quantify the work of fracture of bonds between polymethylmethacrylate plates bonded (a) with the solvent chloroform and (b) with an ultraviolet-curing adhesive. Bond toughnesses of 321±138 J/m2 and 15.3±3.69 J/m2 were recorded for solvent and adhesive bonding respectively. In the case of the adhesive-bonded samples, different patterns of bonded interfaces have been examined, to explore how the macroscopic bond toughness depends on the design of the pattern. The effect of pattern might enhance the bond strength when a crack propagated along discontinuously bonded interface, as it requires greater energetic cost for multiple crack initiations. The results show that when a crack propagates across a discontinuous bonded interface, there is a significant drop in bond toughness of between 26.7% and 66.7% compared to a continuous bonded interface.