Mechanical performance evaluation of thick composites laminates

• Main Author: Yogesh, Visweswaran
• Other Authors: Sunil Chandrakant Joshi
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150769
• Institution: Nanyang Technological University

The final year project aims at investigating mechanical performance of thick and thin composite laminates. The processing parameters for consolidation were investigated with experimental methods for two matrices, FS-3295 and FT-1095. TGA was performed on these two matrices to figure out physical properties, such as, decomposition temperature, and melting point. DSC was conducted to measure temperatures and heat flow. Finally, the project funneled into the study of FS-3295. Thermoplastic fabric was used as the new type of reinforcement for the composites. After understanding the process well, specimens were manufactured for mechanical testing according to ASTM standards. The mechanical responses of laminates subjected to flexural and compressive loads were studied. Laminates with three different thickness were cured, and three sample were tested for each thickness under flexure and compression. The force-displacement and stress strain graphs were plotted using the data obtained from the testing. Useful properties, such as maximum strength, strain, point of crack initiation, yield point, and fracture strength were investigated and compared between the samples with different thickness. In addition, the failure modes are also studied by means of visual and stereo microscopy study. Thicker specimens showed visible signs of delamination where slippage occurred between the layers. Plastic deformation was also greater with increased thickness of laminates. De-laminations and signs of internal fracture were spotted before the laminates failed. The delamination propagates from the center of the specimen and spreads out non evenly. Micro-cracks can also be seen around the peripheral regions. Specimens tested in compression generally showed shear failure which propagates along the 45-degree line. Fiber tearing and cracks are also found on the periphery.