Study of the welding process for the integration of peek/carbon fiber composites for aeronautical applications

Author(s)

Samia Danuta Brejão de Souza

• Document type: Doctoral Thesis
• Institution: Universidade Estadual Paulista (Unesp)
• Defense date: 2017-08-07
• Advisor: Edson Cocchieri Botelho; Luís Rogério de Oliveira Hein

Abstract

The development of advanced polymer composite technology has as one of its functions the joining of materials that combine characteristics such as high mechanical strength and stiffness allied to low specific mass. One of the main problems of the use of polymer composites in structural applications is their effective union for the integration of components. In this sense, recent studies show that welding techniques by electric resistance and induction are promising processes for the union of structural composites, because they are fast methods and both require little surface preparation. This work aims to evaluate the best welding parameters by electric resistance and induction for PEEK (poly(ether-ether-ketone)) laminates reinforced with carbon fibers for aeronautical applications. For this purpose, for resistance welding, the most suitable parameters are evaluated by statistical process control, involving time, electric current and pressure and three several types of resistive elements (300 s, 32 A e 1,5 MPa). For induction welding, the parameters evaluated are time, current and pressure. However, only time and pressure are used for statistical control (current is not variable) (50 s, 150 N). The welded laminates were conditioned in UV, hygrothermal and salt spray chambers, in order to simulate flight conditions, and after these conditions, were characterized in mechanical tests (Lap Shear, Iosipescu, End Notched Flexure and Compression Shear Test), thermal analysis (DMA and TMA) and morphological analysis of fractures from mechanical tests using scanning electron microscopy (SEM) and optical microscopy (OM). In this work, the mechanical properties of the fractions were evaluated. From the results obtained it was observed that although the value of Lap Shear tensile strength was higher for induction welding (24.8 ± 7.0 MPa) in relation to resistance welding (15.82 ± 3.53 MPa), the tensile values of the mechanical properties were higher for resistance welding. For example, for the ENF test, the Average maximum shear stress for the strength was (341.9 ± 55.9) MPa and for the induction was (92.6 ± 17.7) MPa. This was, it can be concluded that considering the parameters processing used, the resistance welding and induction welding are promising for the composites joint of PEEK/carbon fiber for aeronautical application. (AU)

• FAPESP's process: 13/13214-9 - STUDY OF WELDING PROCESS FOR THE INTEGRATION COMPOSITE PEEK / CARBON FIBER WITH FOR AERONAUTICAL APPLICATIONS
• Grantee: Samia Danuta Brejão de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate