PG-EAM - Graduate Program in Aeronautical and Mechanical Engineering
PT EN
Master's Dissertation 2022

Strain rate effects on the fracture toughness of thermoplastic composite laminates subjected to compressive load

Author

João Antonio Brassanini Flores

Concentration Area

Projeto Aeronáutico, Estruturas e Sistemas Aeroespaciais

Defense Date

29/06/2022

Thesis Number

78544

Abstract

This work presents an experimental study on the fracture toughness behaviour of thermoplastic poly-arylene-ether-ketone (PAEK) reinforced with woven carbon fibres, subjected to different strain rates under compressive loading. The specimens were submitted to quasi-static and dynamic conditions. Quasi-static tests were carried out using a servohydraulic universal testing machine at a loading rate of 0.2 mm/min whilst the dynamic tests were performed using a Split Hopkinson Pressure Bar (SHPB) with the specimens subjected to strain rates of 450/s and 750/s. In addition to the data acquisition system, the SHPB apparatus was also equipped with a high-speed image system to monitor the fracture process. The results were evaluated using two different data reduction schemes: (I) digital image correlation (DIC) based strain field measurements and (II) strain energy release rate (SERR) evaluation through the J-integral method, where this scheme takes into account the anisotropy effects of the material. The tested samples were submitted to a fractographic analysis using a Scanning Electron Microscope (SEM) to verify the material fracture aspects at different strain rates. The results revealed a dependency of the fracture toughness on the strain rates, where a fracture toughness enhancement was observed at higher strain rates.

Keywords

Materiais compósitos Laminados Resistência à fratura Tenacidade Deformação Fibras de carbono Ensaios de materiais Varreduras Engenharia de materiais