This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from Skoltech together with colleagues from Xi'an Jiaotong University and the Blagonravov Institute of Mechanical Engineering of the Russian Academy of Sciences, have conducted a systematic study of the flexural properties of pultruded glass fiber composites based on three different thermoplastic matrices: polyphenylene sulfide (PPS), polyamide-6 (PA6) and polypropylene (PP). The results show that a composite's behavior under heating is determined primarily by the polymer matrix rather than the reinforcement.
The findings will help engineers select materials for components operating at elevated temperatures in aviation, automotive, energy and other industries. The work is published in the journal Next Materials. The researchers tested how the strength of the materials changed when heated from room temperature to 280 °C.
The PPS-based composite withstood the highest temperatures: It retained strength even at 260 °C, and at 220 °C, it still retained more than half of its initial stiffness. The PA6-based material was the strongest at room temperature, but its properties gradually deteriorated under heating. The PP-based composite, by contrast, began to degrade at temperatures above 120 °C and completely lost its load-bearing capacity by 160 °C.
Thermal analysis confirmed that the materials' behavior under heating is determined by the properties of the polymer matrix. The PPS composite began to decompose later than the others (at 374 °C) and had the highest glass transition temperature (109 °C), which accounted for its superior performance. The PA6-based material occupied an intermediate position, while the PP composite degraded most rapidly due to its low melting point (151 °C).
"The results will help engineers select the right materials for components operating at high temperatures—for example, in aviation, automotive and energy applications," said Alexander Safonov, the study's principal investigator and an associate professor at the Skoltech Materials Center. "The study showed that even when a composite contains the same reinforcing fiber, its behavior under heating is determined by the polymer matrix. Among the materials studied, PPS is the best choice for hot conditions, while polypropylene should only be used where temperatures do not exceed 100–120 °C." "We tested how existing analytical models describe the temperature degradation of these materials," noted Sukhwant Pal, the first author of the study and a Ph.D. student in the Mathematics and Mechanics program at Skoltech.
"It turned out that there is no universal model—each matrix type requires a different approach. This is important for structural calculations: Choosing the wrong model can lead to errors in estimating load-bearing capacity. We showed that the Mahieux and Bosze models work best for materials with gradual degradation (PPS and PA6), while for polypropylene, where properties drop sharply, simpler models are sufficient." Sukhwant Pal et al, Flexural behavior of thermoplastic pultruded composites at elevated temperatures, Next Materials (2026).
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