Multifunctional glass fiber/polyamide composites with thermal energy storage/release capability

Abstract

Abstract. Thermoplastic composite laminates with thermal energy storage (TES) capability were prepared by combining a glass fabric, a polyamide 12 (PA12) matrix and two different phase change materials (PCMs), i.e. a paraffinic wax microencapsulated in melamine-formaldehyde shells and a paraffin shape stabilized with carbon nanotubes. The melt flow index of the PA12/PCM blends decreased with the PCM concentration, especially in the systems with shape stabilized wax. Differential scanning calorimetry showed that, for the matrices with microcapsules, the values of enthalpy were approximately the 70% of the theoretical values, which was attributed to the fracture of some microcapsules. Nevertheless, most of the energy storage capability was preserved. On the other hand, much lower relative enthalpy values were measured on the composites with shape stabilized wax, due to a considerable paraffin leakage or degradation. The subsequent characterization of the glass fabric laminates highlighted that the fiber and void volume fractions were comparable for all the laminates except for that with the higher amount of shape stabilized wax, where the high viscosity of the matrix led to a low fiber volume fraction and higher void content. The mechanical properties of the laminates were only slightly impaired by PCM addition, while a more sensible drop of the elastic modulus, of the stress at break and of the interlaminar shear strength could be observed in the shape stabilized wax systems.

Application of the thermal energy storage concept to novel epoxy–short carbon fiber composites

“…This could negatively affect the mechanical resistance of the material, and it can be explained by considering that the introduction of MC into polymeric materials produces an increase in the viscosity, which hindered the degassing operation and caused the presence of air bubbles in the cured composite. Similar results were also obtained in a previous work of this group, in which thermoplastic composite laminates with TES capability were prepared by combining a glass fabric and a PA 12 matrix with two different PCMs, that is, the same paraffin microcapsules as used in this work, and a paraffin wax shape stabilized with carbon nanotubes. It was shown that the melt flow index (MFI) of the PA 12/PCM blends considerably decreased with the PCM concentration, which is a clear indicator of a rise in viscosity.…”

“…Similar results were also obtained in a previous work of this group, in which thermoplastic composite laminates with TES capability were prepared by combining a glass fabric and a PA 12 matrix with two different PCMs, that is, the same paraffin microcapsules as used in this work, and a paraffin wax shape stabilized with carbon nanotubes. It was shown that the melt flow index (MFI) of the PA 12/PCM blends considerably decreased with the PCM concentration, which is a clear indicator of a rise in viscosity. Considering the present work, the same trend in pore concentration can be seen in samples with an increasing amount of CF at a constant MC loading (20%).…”

“…No substantial morphological differences can be detected by varying the CF content. The morphological features of the materials are similar to those highlighted in our previous paper on PA 12/MC blends …”

“…Thermal energy can be stored and released in three main ways, namely as sensible heat (due to temperature variations within the material), through thermochemical reactions, or as latent heat, that is, by using phase change materials (PCMs). PCMs are subjected to reversible solid/solid or solid/liquid phase transitions and can be classified as organic, inorganic, or eutectic . The advantages associated with the use of PCMs mainly consist of the possibility of storing a large amount of thermal energy per unit mass in a very narrow temperature range, with very limited volume variations .…”

“…Our group has recently developed multifunctional epoxy–carbon fiber composites containing various percentages of a paraffin shape stabilized with carbon nanotubes (CNTs) . The thermomechanical behavior of a polyamide 12 (PA12)–glass fiber thermoplastic composite with TES functions was also studied . In all these works, it was demonstrated that the introduction of the TES capability comes at the expense of the thermomechanical stability of the system.…”