Effects of Blank Quality on Press-Formed PEKK/Carbon Composite Parts.

Valentina Donadei,Arnt Offringa,Francesca Lionetto,Michael Wielandt,Alfonso Maffezzoli

doi:10.3390/ma11071063

Abstract

The causes of delamination and porosities during press forming of pre-consolidated flat laminates (blanks) made of carbon fiber-reinforced poly(ether ketone ketone) (PEKK) were addressed in this study. In particular, the quality of the blank laminate was investigated before and after infrared heating. The consolidation quality was evaluated by thickness measurements, non-destructive inspection (NDI), and optical microscopy. The experimental results confirmed that deconsolidation phenomena can be related to residual stresses formed during blank forming in an autoclave, then released during infrared heating (IR) of the blank, determining most of the defects in IR heated blanks. These defects, generated at the pre-heating stage, were not fully removed in the consolidation stage of the press forming process. An annealing treatment, performed on autoclave-consolidated blanks above the glass transition temperature of the matrix, was proposed to reduce the formation of defects during IR heating. The stress relaxation phenomena during annealing were modelled using a simple viscoelastic model.

Highlights

Composites are multifunctional materials combining the attractive features of different materials in order to obtain outstanding mechanical and physical properties which can be tailored to meet the requirements of a particular application
After infrared heating (IR) heating, the blank laminates not subjected to any heat treatment presented some macroscopic defects on the surface, like bulges, evidenced by the red arrows in Figure 5a, and macroscopic defects on the surface, like bulges, evidenced by the red arrows in Figure 5a, and delaminations and porosities, as evidenced by the optical microscopy image of Figure 5b
IR heating heating was thethe prepreg manufacture since it was believed that water sorption during storage could cause delamination during since it was believed that water sorption during storage could cause delamination during IR heating

Summary

Introduction

Composites are multifunctional materials combining the attractive features of different materials in order to obtain outstanding mechanical and physical properties which can be tailored to meet the requirements of a particular application. Continuous fiber-reinforced thermoplastic (CFRTP) composites are increasingly being used in automotive and aerospace industries for structural applications thanks to an increased toughness, a low level of moisture uptake, an easy welding ability, a high repair potential, and recycling possibilities [6,7]. Another key advantage of thermoplastic composite materials is given by their potential shorter processing time in comparison to thermosetting matrix composites due to the absence of the curing reaction of the matrix [8,9]. As recently reported in the literature, stamping/press forming is a promising manufacturing process for high-performance thermoplastic composites [15]

Methods

Results

Conclusion