Evaluation of Residual Stress in Modified and Pure HDPE Materials Based on Thermal Diffusivity and Terahertz Phase Spectroscopy

In recent years, the field of polymer materials science has witnessed significant advancements, coupled with a growing emphasis on recycling and sustainability. High-density polyethylene (HDPE) has emerged as a recyclable material, contributing to a greener approach and showcasing immense potential for structural building applications. Notably, HDPE demonstrates superior performance at lower temperatures, making it particularly suitable for various environmental conditions. However, the presence of residual stresses in HDPE can detrimentally impact its performance and even lead to the formation of defects within composite layers.
Traditional destructive methods used for residual stress detection pose challenges as they can introduce additional stresses and potentially reduce the overall component lifespan. Consequently, non-destructive methods have gained significant prominence in this field, assuming an increasingly vital role in accurately assessing residual stresses while preserving the integrity and longevity of HDPE components.
This paper aims to advance the measurement capabilities for assessing residual stress in HDPE by employing both infrared thermography and terahertz (THz) techniques. To enhance the efficiency of infrared thermography, a line-scan thermography (LST) method is employed. To quantify the residual stress, the Fourier transform and Laplace transform are utilized to extract the thermal diffusivity as a quantitative detection coefficient. Additionally, residual stress measurement is conducted using the THz time-domain spectroscopy (THz-TDS) method, which takes into account factors such as refractive index and sample thickness. Experimental validation is performed to assess and compare the feasibility of the proposed techniques. Ultimately, the developed approaches enable the quantitative analysis of residual stresses at different stages of damage utilizing THz-TDS and infrared thermography techniques.