The present work investigates the synergy between pyrolysis and interface degradation (induced by flame exposure) on the residual flexural behavior (three-point bending) of hybrid quasi-isotropic laminates consisting of carbon/glass fibers and a PEEK thermoplastic matrix. The effect of a kerosene flame exposure (116 kW/m2 and 1100°C), on the composites structural integrity is examined as a function of exposure time (300 – 600 – 900 s) and distance to flame. The discussions on fire- and mechanically-induced damage mechanisms are supported by fractographic analysis of specimens (tomography and microscopy). The kerosene flame exposure involves in-plane and through-thickness temperature gradients within the plate specimen. Significant reductions in the flexural stiffness (−65%) and strength (−85%) occur after a 300 s flame exposure compared to virgin state, as the structural integrity of the fire-exposed central zone is severely affected. The effect of prolonged exposure time (ranging from 600 s to 900 s) is moderate on flexural behavior as the barrier formed by an extensive thermally-induced delamination contributes to relatively preserve the plies near the back surface. Regardless the fire exposure time, the specimens in the center seem much degraded with an elastic domain interrupted at 0.7% strain, as the fiber-matrix interface strength has been significantly reduced. The overall residual bending properties of CG/PEEK laminates follow master curves representing the correlations between the amount of char/porosity ratio and the changes in the flexural properties. These master curves provide a relevant design rule for composite parts to be used under critical service conditions (flame exposure).
ZimmermannNWangPH. A review of failure modes and fracture analysis of aircraft composite materials. Eng Fail Anal2020; 115: 104692.
2.
MouritzAP. Fire safety of advanced composites for aircraft. RMIT University, 2006.
3.
BouvetC. Mechanics of aeronautical composite materials. ISTE Ltd ; John Wiley & Sons, Inc., 2017.
4.
Di GiorgioG. Safety and accidents involving aircraft manufactured from polymer composite materials: a review. Aerotec Missili Spaz2023; 102: 337–353.
5.
MouritzAPGibsonAG. Fire properties of polymer composite materials. Springer, 2006.
6.
CarpierYVieilleBMaaroufiMA, et al.Mechanical behavior of carbon fibers polyphenylene sulfide composites exposed to radiant heat flux and constant compressive force. Compos Struct2018; 200: 1–11.
7.
SchuhlerECoppalleAVieilleB, et al.Behaviour of aeronautical polymer composite to flame: a comparative study of thermoset- and thermoplastic-based laminate. Polym Degrad Stabil2018; 152: 105–115.
8.
SchuhlerEChaudharyAVieilleB, et al.Fire behaviour of composite materials using kerosene burner tests at small-scales. Fire Saf J2021; 121: 103290.
9.
GardinerCPMathysZMouritzAP. Post-fire structural properties of burnt GRP plates. Mar Struct2004; 17: 53–73.
10.
VieilleBAucherJTalebL. Comparative study on the behavior of woven-ply reinforced thermoplastic or thermosetting laminates under severe environmental conditions. Mater Des2012; 35: 707–719.
11.
CarpierYVieilleBCoppalleA, et al.About the tensile mechanical behaviour of carbon fibers fabrics reinforced thermoplastic composites under very high temperature conditions. Compos B Eng2020; 181: 107586.
12.
SchmidtDGd’AlmeidaJRM. Effect of temperature exposure on the flexural mechanical behavior of two pultruded composites. Fire Technol2018; 54: 1565–1583.
13.
JiYZhangXWangC, et al.Post-heat flexural properties of siloxane-modified epoxy/phenolic composites reinforced by glass fiber. Polymers2024; 16: 708.
14.
TadiniPGrangeNChetehounaK, et al.Thermal degradation analysis of innovative PEKK-Based carbon composites for high-temperature aeronautical components. Aero Sci Technol2017; 65: 106–116.
15.
CarpierYVieilleBDelpouveN, et al.Isothermal and anisothermal decomposition of carbon fibres polyphenylene sulfide composites for fire behavior analysis. Fire Saf J2019; 109: 102868.
16.
PatelPHullTRLyonRE, et al.Investigation of the thermal decomposition and flammability of PEEK and its carbon and glass-fibre composites. Polym Degrad Stabil2011; 96: 12–22.
17.
SwannJDDingYStoliarovSI. Comparative analysis of pyrolysis and combustion of bisphenol A polycarbonate and poly(ether ether ketone) using two-dimensional modeling: a relation between thermal transport and the physical structure of the intumescent char. Combust Flame2020; 212: 469–485.
18.
DoddsNGibsonAGDewhurstD, et al.Fire behaviour of composite laminates. Compos Appl Sci Manuf2000; 31: 689–702.
19.
Márquez CostaJP. Review of fracture characterization by delamination and debonding of polymer composite materials and bonded interfaces subjected to high temperature. Mech Adv Mater Struct. 2025; 1–30.
20.
VieilleBTalebL. About the influence of temperature and matrix ductility on the behavior of carbon woven-ply PPS or epoxy laminates: notched and unnotched laminates. Compos Sci Technol2011; 71: 998–1007.
21.
CarpierYBourdetADelpouveN, et al.Thermal decomposition study of carbon fiber-reinforced polyphenylene sulfide at high heating rates met under fire exposure. J Therm Anal Calorim2024; 149: 6039–6050.
22.
LattimerBYOuelletteJTrellesJ. Measuring properties for material decomposition modeling. Fire Mater2011; 35: 1–17.
23.
VieilleBCoppalleALe PluartL, et al.Kerosene flame behaviour of C/PEKK composite laminates: influence of exposure time and laminates lay-up on residual mechanical properties. Compos B Eng2021; 222: 109046.
24.
AspinallTJErskineELTaylorDC, et al.Influence of carbon fibre orientation and heat flux on the thermomechanical response of CFRP using small-scale apparatus. Fire Saf J2024; 146: 104142.
25.
VieilleBCoppalleACarpierY, et al.Influence of matrix nature on the post-fire mechanical behaviour of notched polymer-based composite structures for high temperature applications. Compos B Eng2016; 100: 114–124.
26.
VieilleBLefebvreCCoppalleA. Post fire behavior of carbon fibers polyphenylene Sulfide- and epoxy-based laminates for aeronautical applications: a comparative study. Mater Des2014; 63: 56–68.
27.
VieilleBCoppalleASchuhlerE, et al.Influence of kerosene flame on fire-behaviour and mechanical properties of hybrid carbon glass fibers reinforced PEEK composite laminates. Compos Struct2022; 279: 114786.
28.
LinLVieilleBBouvetC. About the influence of a thermal aggression on the tensile behaviour of hybrid PEEK thermoplastic laminates. Compos Struct2024; 333: 117945.
29.
PatelPHullTRMcCabeRW, et al.Mechanism of thermal decomposition of poly(ether ether ketone) (PEEK) from a review of decomposition studies. Polym Degrad Stabil2010; 95: 709–718.
30.
GibsonAGTorresMEOBrowneTNA, et al.High temperature and fire behaviour of continuous glass fibre/polypropylene laminates. Compos Appl Sci Manuf2010; 41: 1219–1231.
31.
FeihSMouritzAP. Tensile properties of carbon fibres and carbon fibre–polymer composites in fire. Compos Appl Sci Manuf2012; 43: 765–772.
32.
YararEŞahinAEKaraH, et al.Thermal aging effect on mechanical properties of polyamide 6 matrix composites produced by TFP and compression molding. Polym Compos2024; 45: 2869–2884.
33.
LinLVieilleBBouvetC, et al.Translaminar fracture behavior of hybrid woven-ply peek thermoplastic laminates under isothermal and kerosene flame exposure. J Compos Mater2025; 59: 1965–1981.
34.
GibsonAGTorresMEOBrowneTNA, et al.High temperature and fire behaviour of continuous glass fibre/polypropylene laminates. Compos Appl Sci Manuf2010; 41: 1219–1231.
35.
KawAK. Mechanics of composite materials. CRC Taylor & Francis, 2006, vol 2.
36.
GabrionXPlacetVTrivaudeyF, et al.About the thermomechanical behaviour of a carbon fibre reinforced high-temperature thermoplastic composite. Compos B Eng2016; 95: 386–394.
37.
JiaZLiTChiangF, et al.An experimental investigation of the temperature effect on the mechanics of carbon fiber reinforced polymer composites. Compos Sci Technol2018; 154: 53–63.
38.
FriedrichK. Fractographic analysis of polymer composites. Compos Mater1989; 6: 425–487.
39.
GreenhalghE. Defects and damage and their role in the failure of polymer composites. Failure analysis and fractography of polymer composites. Elsevier, 2009, pp. 356–440.
40.
ÇetinBKorkusuzOBÖzzaimP, et al.The effect of matrix and interface properties modified by annealing on solid particle erosion behavior of carbon fiber reinforced polyetheretherketone. Polym Compos2023; 44: 6212–6227.
41.
LinLVieilleBBouvetC, et al.Simple analytical modeling of residual flexural properties of hybrid PEEK thermoplastic composite laminate under kerosene flame exposure. Compos Struct2025; 373: 119648.
42.
ASTM International. ASTM D7264: test method for flexural properties of polymer matrix composite materials. ASTM International, 2015.
43.
MouritzAP. Post-fire flexural properties of fibre-reinforced polyester, epoxy and phenolic composites. J Mater Sci2002; 37: 1377–1386.
