On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

Abstract

Automatic lay-up and in-situ consolidation with thermoplastic composite materials is a technology under research for its expected use in the profitable manufacturing of structural aeronautical parts. This study is devoted to analysing the possible effects of thermal degradation produced by this manufacturing technique. Rheological measurements showed that there is negligible degradation in PEEK for the temperatures reached during the process. Thermogravimetric analysis under linear heating and constant rate conditions show that thermal degradation is a complex process with a number of overlapping steps. A general kinetic equation that describes the degradation of the material with temperature has been proposed and validated. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that there is no remarkable degradation. The use of a combination of in-situ and ex-situ experimental techniques, including kinetic modelling, not only provides reliable information about degradation but also allows setting optimal processing conditions.

Influence of composite preform fabrication on the integrity of poly‐aryl‐ether‐ketone matrices

“…Conversely, the oxidative environment induces an exponential increase of PEEK 1 viscosity: the level of viscosity if multiplied by a factor 5 within 40 min. This change of viscosity is a consequence of crosslinking as already reported by several authors 34,31,44,32 …”

“…Whatever the type of preform, PEEK and PEKK matrices always degrade according to the process of chain breakage and crosslinking described by many authors 25,23,21,24 . The same evidence of the degradation process as reported in the literature has been observed such as the decrease in decomposition temperature by TGA, 9,31,28 the decrease in crystallization temperature 43,28 or the increase in viscosity 31,44,32,34 . The comparison of semi‐finished products of different architectures indicates that the transformation of the matrix into yarn or film as well as the presence of additives have an effect on the thermal stability of PAEK.…”

“…This change of viscosity is a consequence of crosslinking as already reported by several authors. 34,31,44,32 Both PEEK Yarn 1 and PEEK Yarn 2 exhibit an initial viscosity that is lower than the raw material, no matter whether they were tested in air or argon atmosphere. This can be due to the lower M w of yarn references according to Mark-Houwink equation, but also to a lubricating effect of the sizing that is generally composed of low-molar mass aliphatic molecules.…”

A comparison of mechanical properties and X-ray tomography analysis of different out-of-autoclave manufactured thermoplastic composites

“…However, the automatic lamination of thermoplastic composites is still under research, and consequently achieving the same production level as thermoset processing is challenging. Even though it was a technology studied during the decade of the 1980s, [1][2][3][4] there is a renewed interest in thermoplastic lamination [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] that could be mainly attributed to technological advances, such as the recent development of promising heat sources which may offer low power consumption as diode laser, modern industrial automated equipment like multi-tow heads, and higher quality thermoplastic prepregs.…”

“…Automatic lamination of thermoplastic composites is a high-complexity process where many physical phenomena take place, such as thermal transfer, crystallization and intimate contact, among others. 5,10,21,28 In contrast with more conventional manufacturing methods, the key phenomena occur during a very short time (typically few milliseconds). At the time when the resin is melted, the polymer chains are diffused and the voids occluded into the raw tapes must be evacuated during the consolidation of the roller, followed by ultra-fast cooling down, in the order of 10,000-15,000 C/min.…”