Tensile Fracture and Failure Behavior of Thermoplastic Starch with Unidirectional and Cross‐Ply Flax Fiber Reinforcements

Abstract

Thermoplastic starch (MaterBi®) based composites containing flax fibers in unidirectional and crossed‐ply arrangements were produced by hot pressing using the film stacking method. The flax content was varied in three steps, viz. 20, 40 and 60 wt.‐%. Static tensile mechanical properties (stiffness and strength) of the composites were determined on dumbbell specimens. During their loading the acoustic emission (AE) was recorded. Burst type AE signal characteristics (amplitude, width) were traced to the failure mechanisms and supported by fractographic inspection. The mechanical response and failure mode of the composites strongly depended on the flax content and the flax fiber lay‐up. It was established that the tensile strength increases until 40 wt.‐% flax fiber content but stays almost constant above this value. In the case of 40 wt.‐% unidirectional fiber reinforcement, the tensile strength of the composite was 3 times greater than that of the pure starch matrix. The flax fiber reinforcement increased the tensile modulus of the pure starch by several orders of amplitude.SEM picture of the fracture surface of a composite with UD flax reinforcement.magnified imageSEM picture of the fracture surface of a composite with UD flax reinforcement.

Fracture behaviour of natural fibre reinforced composites

“…From these results, we found that high-amplitude AE events are derived from the fracture of single fibre, and that low amplitude AE events might be derived from fibre splitting among the single fibres. Similar fracture behaviour of natural fibre has been reported in flax fibre reinforced composites [15].…”

Microfibrillated cellulose and new nanocomposite materials: a review

“…Fabrication of composites based on organic or inorganic reinforcement is another possible solution to improve the performance of starch films. Application of fillers such as clays (Huang et al 2004;Yoon and Deng 2006;Lee et al 2007a, b;Cyras et al 2008), natural fibers (Romhany et al 2003;Alvarez et al 2004;Ma et al 2005;Duanmu et al 2007) cellulose whiskers (Cao et al 2008;Mathew et al 2008), or microcrystalline cellulose (Kumar and Singh 2008;Ma et al 2008a;Kadokawa et al 2009) are reported. MFC and BC have also been reported as promising candidates for starch reinforcement (Grande et al 2008;Mondragón et al 2008;Sreekala et al 2008) and some of these applications are discussed here.…”

Advanced Nano-biocomposites Based on Starch

“…Starch biocomposites can be produced with the reinforcement by cellulose fibers (potato pulp, bleached leafwood fibers, fibers from bleached eucalyptus pulp, and flax and jute fibers) (Alvarez et al 2004;Averous and Boquillon 2004;Avérous 2002Avérous , 2007Avérous et al 2001;Carvalho et al 2003;Curvelo et al 2001;Dufresne et al 2000;Funke et al 1998;Lawton et al 2004;Matsui et al 2004;Romhány et al 2003;Wollerdorfer and Bader 1998) and lignin fillers (Baumberger et al 1998a, b;Baumberger 2002). When the fillers are nanoscaled, nanocomposites are obtained.…”