Fire reaction and post-fire impact properties of flax fibre reinforced composites containing intumescent flame retardants

Abstract

The current research aims at investigating the fire reaction and post-fire impact characteristics of flax fibre reinforced composites based on different polymer matrices, such as epoxy resin and polypropylene (PP). The effects of stacking sequences of polymer sheets and flax fabrics within the composites are explored by a cone calorimeter. Heat release and smoke production results indicate that a top surface and number of flame-retardant polymer layers played significant roles in determining the fire reaction properties. Furthermore, post-fire impact properties of flax-epoxy and flax-PP composites depending on burning periods are analysed in this study at the first time. A fully instrumented drop-weight impact testing demonstrates that an increase in heat exposure time led a gradual decrease in impact properties of the composites due to fire-induced damages on fibres and polymers. However, pre-melting and re-consolidation of PP are beneficial to have higher impact energy and force of the flax-PP composite over those of the flax-epoxy counterpart. In addition, the char formation of composites due to intumescent flame retardant enhances the fire reaction properties of composites, whereas there is no significant influence on the post-fire impact characteristics due to highly brittle nature of carbonaceous char.

Influence of temperature degradation on the low velocity impact behavior of hybrid thermoplastic PEEK laminates

“…When it comes to test the impact behavior after severe thermal degradation, there are very few studies available in the literature. Different methodologies and technical means were considered to induce thermal damages within composite laminates: cone calorimeter, 42 flame-throwing gun device, 43 small-scale fire apparatus. 44 Ulven et al used a propane torch apparatus based on a Burn-Through Test set-up to conduct small-scale fire exposure tests producing a steady flame normal to a plate surface.…”

“…Similarly, damage to composite laminates in a fire will significantly affect their structural integrity and post-fire performance. 43 A linear char front develops through the thickness of laminated composites because of the decomposition of the matrix within the laminates, which commonly results in two well defined regions 44 : a charred one with significant delamination near the exposed surface and a less degraded one near the back surface. The residual char is very porous, brittle, and does not provide structural integrity to the fibers.…”