PSI - Issue 68

Danilo D’Andrea et al. / Procedia Structural Integrity 68 (2025) 746–755 D’Andrea et al./ Structural Integrity Procedia 00 (2025) 000–000

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Chiellini 2020), automotive (Wiese, Thiede, and Herrmann 2020), civil engineering (Jamali, Kaushal, and Najafi 2021) and electronics (Divakaran et al. 2022; Ryan et al. 2022). Nylon PA12 is one of the most widely used polymers in biological, food and pharmaceutical applications, due to its high chemical stability and temperature resistance. When reinforced with carbon fibres, it can be used for prosthetic devices and biological components such as pacemakers (Shakiba et al. 2021). Lammens et al. (Lammens et al. 2017) have evaluated the mechanical behaviour of selectively laser sintered (SLS) nylon (PA-12) through tensile, compression, shear, and relaxation tests. It was observed that the tensile strength of the sintered PA-12 is lower than the shear strength. Dul et al (Dul, Fambri, and Pegoretti 2021) have analysed the effect of short carbon fibre (CF) on the mechanical, electrical and piezoresistivity properties of 3D-printed polyamide (PA) composite, obtained by fused filament fabrication (FFF) process. The results revealed that the carbon fibres effectively improved all assessed mechanical properties of PA/CF composites respect to the neat PA. Sommer et al (Sommer, Stockfleet, and Hellmann 2024) have studied the mechanical properties of SLS polyamide components, produced with various different process parameters (laser power, scan speed, and build temperature) as well as environmental testing conditions. They pointed out that by varying the energy density using different parameters, PA exhibits large differences for all levels of fatigue behaviour. The aim of the present work regards the study of mechanical properties of PA reinforced with 15% of carbon fibres (CF), obtained by fused deposition modelling. Infrared Thermography has been adopted to monitor the temperature evolution during static and fatigue tests, in order to apply energy methods, such as Static Thermographic Method (STM) (A. Risitano and Risitano 2013) and Risitano Thermographic Method (RTM)(La Rosa and Risitano 2000), to evaluate the mechanical behavior of Nylon (D’Andrea et al. 2022; D’andrea et al. 2022).

Nomenclature AM

Additive Manufacturing

PA Polyamide FDM Fused Deposition Modelling RFM Rapid Testing Machine DIC Digital Image Correlation CF Carbon Fibres SLS Selective Laser Sintering STM Static Thermographic Method RTM Risitano Thermographic Method CA Costant Amplitude ΔT st Stabilization Temperature Ni Number of Cycles Φ Energy Parameter ρ Material Density σ 1 Principal Stress Applied T 0 Absolute Temperature K m Thermoelastic Constant y Yielding Stress lim Static Limit Stress 2. Theoretical Background

The RTM is a methodology that consist in determining the stabilization temperature associated to the stress level applied to the specimen. Surface temperature trend shows three different phases: the first phase in characterized by a temperature growth until a stabilization temperature is reached. Temperature remains constant throughout the second phase, since it reached its stabilization value (ΔT st ) and rises again in the third phase before the failure. It is possible