Composite Materials Testing

Mert, Hatice Hande, et al. Thermal Science and Engineering Progress 46 (2023): 102213.

This study investigates the preparation and thermal energy storage (TES) performance of composite materials, specifically composite phase change materials (PCMs), for cold thermal energy storage. The composite PCMs were synthesized by impregnating n-pentadecane (n-PD) into emulsion-templated porous polymer composites, with various fillers including graphitic carbon nitride (g-C₃N₄), alumina (Al₂O₃), and a combination of g-C₃N₄/Al₂O₃. The effect of these fillers on the thermal conductivity and energy storage performance of the composites was evaluated.

X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis revealed that the composite matrices exhibited stable thermal properties, with homogeneous distribution of fillers. The results from the T-history method indicated an enhancement in heat transfer for composites containing 1 wt% fillers, with the greatest improvements seen in composites with g-C₃N₄ and g-C₃N₄/Al₂O₃.

Differential scanning calorimetry (DSC) showed that the composite PCMs had phase transition temperatures between −7.02°C and 12.63°C, with latent heat values ranging from 79.49 J/g to 121.5 J/g. The composites demonstrated efficient thermal storage capability, maintaining over 96% of their latent heat storage and release performance. These composite materials are well-suited for cold storage applications, such as perishable goods transport and cold storage containers, thanks to their favorable phase change properties and thermal energy storage capacities.

Mahmud, S. H., et al. journal of materials research and technology 26 (2023): 6623-6635.

This study investigates the impact of gamma (γ) irradiation on the mechanical and moisture resistance properties of jute/polyester and glass/polyester composite materials. Both composites were fabricated using woven jute and glass fibers as reinforcements in an unsaturated polyester resin matrix via compression molding. The performance of these composites was compared before and after exposure to γ-irradiation at a dose of 5 kGy.

The results show that glass/polyester composites exhibited superior mechanical properties compared to jute/polyester composites, attributed to the stronger interfacial bonding between glass fibers and the polyester matrix. After γ-irradiation, both composites experienced significant improvements in tensile strength, bending strength, tensile modulus, bending modulus, and impact strength. For jute/polyester composites, the increases were 14%, 28%, 20%, 21%, and 13%, respectively, while glass/polyester composites showed increases of 13%, 27%, 15%, 14%, and 22%.

Moisture uptake tests revealed higher water absorption for jute/polyester composites due to the hydrophilic nature of jute fibers. However, γ-irradiation slightly improved the moisture resistance for both composites.

These findings confirm that γ-irradiation is an effective method for enhancing the mechanical and moisture resistance properties of both natural fiber-reinforced composites (NFRCs) and synthetic fiber composites, offering promising industrial applications. However, further life cycle assessments and commercial feasibility studies are necessary to evaluate the environmental impacts of this treatment.

Jadal, Mariam, et al. Thermal Science and Engineering Progress 33 (2022): 101336.

This study focuses on the crystallization kinetics of phase change composite materials (PCMs), specifically paraffin RT70HC embedded in Compressed Expanded Natural Graphite (CENG) matrix. The research investigates the solidification behavior of this composite material, where two-phase transformations occur during cooling. A detailed experimental protocol, including differential scanning calorimetry (DSC) analysis and macro-DSC techniques, was employed to model the crystallization process.

The findings show that the crystallization kinetics of paraffin-based PCM remains unchanged when embedded in the CENG matrix, indicating that CENG does not act as a nucleating agent. The experimental results were validated across different scales, including small-scale plate and packed-bed heat storage exchanger configurations. Additionally, the study reveals that there is no scale effect on the crystallization behavior, and the kinetic properties remain consistent regardless of the PCM matrix shape, size, or cooling rate.

The kinetic model was successfully implemented in a finite element simulation using COMSOL® to predict the temperature evolution of the PCM during cooling. The Nakamura formulation was used to model the isothermal cooling process, considering the phase change temperature history. This comprehensive approach provides a reliable methodology for determining the kinetic parameters of CENG-PCM composites, offering insights for the design of efficient thermal energy storage systems. Future work will focus on refining the model to fully determine the kinetic parameters of the second transformation phase.