pps proceeding - Abstract Preview
pps proceeding
Symposium: G06 - Polymer composites
Oral Presentation
 
 

Manufacturing Silk/Epoxy Composite Laminates: Challenges and Opportunities

Hamidi Youssef K. (1)*, Yalcinkaya M. Akif (2), Guloglu Gorkem E. (2), Pishvar Maya (2), Amirkhosravi Mehrad (2), Altan M. Cengiz (2)

(1) Ecole Nationale Supérieure des Mines de Rabat - Rabat - Morocco, (2) School of Aerospace and Mechanical Engineering, University of Oklahoma - Oklahoma - USA

Application of natural fibers in polymer composites is gaining popularity in several industries pursuing environmentally friendly products. Among the natural fibers with proven potential applications, silk fibers have recently received considerable attention from researchers. Silk fibers provide higher mechanical properties compared to other commonly used natural fibers such as sisal, jute, and hemp. Silk may also exhibit comparable specific mechanical properties to glass fibers. However, silk composite laminates are rarely used in commercial products due to a number of fabrication challenges. This paper investigates such challenges for silk/epoxy laminates, especially issues related to manufacturing and preform architecture. First, challenges arising from preform architecture (i.e., random and woven preforms) are presented. Unlike glass fibers for which random mats are easier to manipulate, handling random silk preform proves to be more challenging, particularly compared to woven silk fabrics. The random silk/epoxy laminates show higher thickness variation and lower compaction, yielding lower fiber content. Second, fabrication of laminates by vacuum bag/wet layup and Vacuum Assisted Resin Transfer Molding (VARTM) processes are presented. VARTM is found to be more appropriate for silk/epoxy laminate fabrication, as it allows a uniform impregnation of the silk preform, yielding higher part quality and limited void formation. Moreover, applying 0.21MPa (30psi) external pressure to the VARTM laminates allows to increase the fiber content of both random and woven silk/epoxy laminates from ~17 and ~30% to ~21 and ~33%, respectively. In contrast, silk preform wetting in wet layup, which is operator dependent, is difficult to achieve; and the produced laminates contain excessive void content. Furthermore, SEM images show a weak silk/epoxy adhesion in laminates fabricated without external pressure. Finally, the mechanical performance of these laminates is assessed. The woven silk/epoxy laminates fabricated by pressurized VARTM exhibits the highest improvement in the specific flexural strength and stiffness over pristine epoxy with 30 and 65% increase, respectively.