Effect of processing temperature on the static and dynamic mechanical properties and failure mechanisms of flax fiber reinforced composites

In this paper, the effects of processing temperatures on both static, dynamic and time-dependent mechanical properties of flax fibers and their composites were investigated. Initially, the chemical component variations of flax fibers processed at different temperatures were ascertained by using Fourier transform infrared spectrometry (FTIR) and X-ray diffraction (XRD). Tensile tests were further conducted to investigate the effect of temperature on the strength, modulus and failure elongation of the fibers and flax fiber reinforced composites (FFRCs). The corresponding fracture mechanisms were characterized by in-situ acoustic emission (AE) technique. The durability and the energy dissipation and absorption capability of these FFRCs were evaluated with tensile-tensile fatigue tests and drop weight impact (DWI) tests. The results showed that there was a vital turning temperature, exceeding which degradation of partial cellulose, hemicellulose and lignin occurs, which introduced damage into the chemical structures of flax fibers and impaired their mechanical performance. The mechanical properties of FFRCs dominated by flax fiber including tensile behaviors, long-term durability and energy dissipation and absorption capability consequently deteriorate when treated temperature exceeds the turning point.