Characterisation of BMI composite materials
Woon, Ianson Tian Huang
Date of Issue2016
School of Mechanical and Aerospace Engineering
Due to the heterogeneity of composite materials, it is known that composite materials tend to be vulnerable to delamination. As such, this work aims to investigate the Mode I and Mode II interlaminar fracture toughness of the Bismaleimide (BMI) specimens. This is seen of importance because propagation of delamination occurs without visibly detectable sign, and understanding the BMI material’s resistance to interlaminar fracture will allow future applications to develop failure criteria for future product selection. The Double Cantilever Beam (DCB) Mode I and End Notch Flexure (ENF) Mode II standard tests were conducted on the BMI samples for both dry and wet with [0/90] and [-45/45] layout samples. Both tests were performed so that the fracture toughness, G, can be calculated during initiation and propagation due to tensile or shear load force. Results from the interlaminar Mode I fracture toughness of the BMI [0/90] layout samples showed a variable trend towards slight increase or slight decrease, depending on the amount of moisture and temperature during aging. Results indicated that the 50°C wet samples had the highest resistance to delamination during initiation and propagation. Furthermore, results from the interlaminar Mode II fracture toughness of the BMI [0/90] layout samples indicated that the increase in moisture and temperature during aging enhances the resistance during initiation and propagation. However, the Mode II fracture resistance showed a decreasing trend along with an increase in moisture content for the case of BMI [-45/45] layout samples. Finally, at the end of the two standard tests, the delamination results with significant difference in resistance were further backed up with observations seen in the morphological analysis performed by using a Scanning Electron Microscope (SEM).
Final Year Project (FYP)
Nanyang Technological University