https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 05 Mar 2026 19:54:36 GMT 2026-03-05T19:54:36Z http://hdl.handle.net/10985/25861 Anomalous hydraulic fluid absorption by carbon fiber/PEKK composites: physical and mechanical aspects LESIMPLE, Gwladys; ILIOPOULOS, Ilias; MIQUELARD-GARNIER, Guillaume; BENETHUILIERE, Thibaut; BIZET, Stéphane; FAYOLLE, Bruno AbstractCarbon fiber (CF)/polyetherketoneketone (PEKK) composites are exposed to Skydrol, a hydraulic fluid made of phosphate esters widely used in the aviation field. The present study investigates Skydrol absorption of CF/PEKK composite layups and the associated PEKK matrix. A significant unexpected increase of Skydrol uptake is observed for cross‐ply composites (0.50%) compared to unidirectional ones (0.06%), independently of ply number. The use of ‘model’ fluids like water and ethanol allows to identify the origin of this anomalous Skydrol absorption in the case of cross‐ply layup. We propose that the latter involves an imbibition process governed by the fluid surface tension and the presence of submicronic cavities. SEM imaging of composite cross‐section after ion beam polishing confirms fiber‐matrix submicronic debonding in the interlaminar region in the cross‐ply composite. SEM–EDX confirms the presence of Skydrol into the submicronic cavities. Despite this anomalous absorption, off‐axis tensile testing as well as ILSS testing show no significant impact of Skydrol on CF/PEKK mechanical properties with less than 10% difference compared to the initial values. Highlights Absorption by diffusion of Skydrol in neat PEKK and CF/PEKK composites, Link between fluid surface tension and anomalous Skydrol absorption, Evidence of submicronic cavities in CF/PEKK composites by means of SEM–EDX, Low impact of Skydrol on CF/PEKK mechanical properties. Wed, 01 May 2024 00:00:00 GMT http://hdl.handle.net/10985/25861 2024-05-01T00:00:00Z LESIMPLE, Gwladys ILIOPOULOS, Ilias MIQUELARD-GARNIER, Guillaume BENETHUILIERE, Thibaut BIZET, Stéphane FAYOLLE, Bruno AbstractCarbon fiber (CF)/polyetherketoneketone (PEKK) composites are exposed to Skydrol, a hydraulic fluid made of phosphate esters widely used in the aviation field. The present study investigates Skydrol absorption of CF/PEKK composite layups and the associated PEKK matrix. A significant unexpected increase of Skydrol uptake is observed for cross‐ply composites (0.50%) compared to unidirectional ones (0.06%), independently of ply number. The use of ‘model’ fluids like water and ethanol allows to identify the origin of this anomalous Skydrol absorption in the case of cross‐ply layup. We propose that the latter involves an imbibition process governed by the fluid surface tension and the presence of submicronic cavities. SEM imaging of composite cross‐section after ion beam polishing confirms fiber‐matrix submicronic debonding in the interlaminar region in the cross‐ply composite. SEM–EDX confirms the presence of Skydrol into the submicronic cavities. Despite this anomalous absorption, off‐axis tensile testing as well as ILSS testing show no significant impact of Skydrol on CF/PEKK mechanical properties with less than 10% difference compared to the initial values. Highlights Absorption by diffusion of Skydrol in neat PEKK and CF/PEKK composites, Link between fluid surface tension and anomalous Skydrol absorption, Evidence of submicronic cavities in CF/PEKK composites by means of SEM–EDX, Low impact of Skydrol on CF/PEKK mechanical properties. http://hdl.handle.net/10985/20462 Quantitative Structural Study of Cold-Crystallized PEKK TENCE-GIRAULT, Sylvie; QUIBEL, Jonathan; CHERRI, Alexis; BIZET, Stéphane; ILIOPOULOS, Ilias; FAYOLLE, Bruno; ROLAND, Sébastien Poly(ether ketone ketone) (PEKK) is a semicrystalline polymer investigated for highly demanding applications in aerospace, transportation, electronics, and oil & gas industries. The properties required for these applications, such as thermomechanical and chemical stability, are intimately linked to the crystalline state of the material. PEKK exhibits a polymorphism that depends, among other factors, on its thermal history. The control and quantification of the crystalline state of PEKK is the subject of this study. Amorphous PEKK (T/I = 60/40, where T stands for terephthalic and I for isophthalic units) films were cold-crystallized at various crystallization temperatures, T-C, from 180 to 280 degrees C in a ventilated oven. Based on a quantitative analysis of small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) data, we propose for the first time a methodology to obtain detailed information about the crystalline state of PEKK: total crystallinity, relative amount and stability of crystalline forms, form I and form II, and melting enthalpy of 100% crystallized PEKK. The evolutions of each crystalline form and the total crystallinity with T-C were deduced. The amount of each crystalline form, form I and form II, can be tuned by controlling the heating rate to 280 degrees C. The evolution of the crystalline lamellar thickness and periodicity as well as the crystalline amount and cell parameters with T-C were interpreted and discussed in relation to the published results on PEEK, PEKK (100% T), and PEKK (100% I). Finally, the melting enthalpy of a 100% crystallized PEKK copolymer (T/I = 60/40), Delta H-m(100%) = (202 +/- 20) J/g, was estimated. Fri, 01 Jan 2021 00:00:00 GMT http://hdl.handle.net/10985/20462 2021-01-01T00:00:00Z TENCE-GIRAULT, Sylvie QUIBEL, Jonathan CHERRI, Alexis BIZET, Stéphane ILIOPOULOS, Ilias FAYOLLE, Bruno ROLAND, Sébastien Poly(ether ketone ketone) (PEKK) is a semicrystalline polymer investigated for highly demanding applications in aerospace, transportation, electronics, and oil & gas industries. The properties required for these applications, such as thermomechanical and chemical stability, are intimately linked to the crystalline state of the material. PEKK exhibits a polymorphism that depends, among other factors, on its thermal history. The control and quantification of the crystalline state of PEKK is the subject of this study. Amorphous PEKK (T/I = 60/40, where T stands for terephthalic and I for isophthalic units) films were cold-crystallized at various crystallization temperatures, T-C, from 180 to 280 degrees C in a ventilated oven. Based on a quantitative analysis of small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) data, we propose for the first time a methodology to obtain detailed information about the crystalline state of PEKK: total crystallinity, relative amount and stability of crystalline forms, form I and form II, and melting enthalpy of 100% crystallized PEKK. The evolutions of each crystalline form and the total crystallinity with T-C were deduced. The amount of each crystalline form, form I and form II, can be tuned by controlling the heating rate to 280 degrees C. The evolution of the crystalline lamellar thickness and periodicity as well as the crystalline amount and cell parameters with T-C were interpreted and discussed in relation to the published results on PEEK, PEKK (100% T), and PEKK (100% I). Finally, the melting enthalpy of a 100% crystallized PEKK copolymer (T/I = 60/40), Delta H-m(100%) = (202 +/- 20) J/g, was estimated.