Researcher(s)
- Shawn Yong, Mechanical Engineering, University of Delaware
Faculty Mentor(s)
- Sai Pradeep, Research and Development Engineer at Center for Composite Materials, University of Delaware
- Amit Deshpande, Mechanical Engineering, University of Delaware
Abstract
Shawn Yong, Sai Pradeep, Amit Deshpande, Srikanth Pilla
Thermoplastic composites undergo reversible phases from solid to molten states when heated, leading to the formation of porous voids, a process known as deconsolidation (DE). Most studies on deconsolidation have focused on glass or carbon fiber thermoplastic composites, with limited research on more sustainable flax fiber composites. This study aims to characterize the thermal deconsolidation of flax fiber-reinforced thermoplastic composites. The composites used in the study were 4×4 twill weave flax fiber polypropylene (FF-PP) with a 34% fiber volume fraction and 2×2 twill weave glass fiber polypropylene (GF-PP) with a 45% fiber volume fraction. Four samples were prepared: two deconsolidated samples of FF-PP-DE and GF-PP-DE and compared with two as-received consolidated versions. Thermal deconsolidation was done by heating the samples in a convection oven until they reached 170°C and were cured at room temperature. Micro-CT imaging was done on the samples to inspect the cross sections for voids before and after deconsolidation. An image processing software was used to quantify voids and deconsolidation. The deconsolidated samples showed more void volume than their consolidated counterparts and FF-PP-DE had more void volume than GF-PP-DE. Differential scanning calorimetry (DSC) was conducted on the samples, where they were heated to 200°C and cooled to room temperature. FF-PP showed greater enthalpy than GF-PP in both consolidated and deconsolidated forms. FF-PP-DE samples exhibited higher enthalpy than its consolidated counterparts whereas the GF-PP-DE had similar enthalpy to its consolidated counterparts. Thermogravimetric analysis (TGA) was conducted on the samples, where they were heated up to 200°C. The FF-PP-DE samples showed a greater mass loss, which could be attributed to water loss, while GF-PP-DE samples showed no mass loss. Flax fiber had different deconsolidation characteristics from glass fiber. The higher amount of void content in FF-PP-DE compared to GF-PP-DE is attributed to the greater water absorptivity of flax fibers, leading to water vapor escape and more void formations upon heating compared to the GF-PP-DE.