• In-situ thermal Raman mapping using CNTs as sensing media enables quantitative visualization of local thermal stress distribution at CNT/CF/epoxy interfaces.
• The G' band of CNTs shifts to lower wavenumbers with increasing temperature, with a maximum shift of 2.43 cm−1 at 100°C, indicating tensile stress evolution.
• Electrophoretic deposition effectively constructs CNT/CF hybrid fibers, improving interfacial bonding and stress transfer compared to conventional CF/epoxy composites.
• This technique provides a non-contact, precise method for assessing thermal stress in fiber-reinforced composites, crucial for high-temperature applications.