Theoretical characterization of the temperature-dependent ultimate tensile strength of short-fiber-reinforced polymer composites

Short fiber/polymer composites (SFPCs) are increasingly applied in the field of high-temperature structures. Its reliability at high temperatures has always been the core issue concerned by researchers. Here, utilizing the Force-Heat Equivalence Energy Density Principle, we developed a physically based model of temperature-dependent ultimate tensile strength (TDUTS) for SFPCs. This model quantitatively considers the evolution of residual thermal stress, interface, fiber, and matrix performance as temperature increases. Meanwhile, the influence of fiber agglomeration frequently observed in composites and fiber orientation and length distribution is taken into account in the proposed model. The model predictions over a wide temperature range are validated against the experimental data available from the literature, indicating its reasonability and accuracy. The comparison with Kelly-Tyson model and Li's model is also performed. Additionally, the quantitative effects of the fiber agglomeration and interfacial shear strength on the TDUTS are discussed in detail. The present research not only provides an accurate and feasible approach to estimate the TDUTS of SFPCs, but also offers some helpful insights for the fabrication and design of such composites.

Automated summary

Short fiber/polymer composites are increasingly used in high-temperature structures, with a temperature-dependent ultimate tensile strength model developed in this study considering the evolution of residual thermal stress, interface, fiber, and matrix performance, as well as the effects of fiber agglomeration and orientation distribution. The model's predictions are validated against experimental data, showing reasonable accuracy and providing insights for fabrication and design of such composites. Discussions on the quantitative effects of fiber agglomeration and interfacial shear strength on the ultimate tensile strength are also included.