Thermo-mechanical performance of poly(lactic acid)/flax fibre-reinforced biocomposites

Abstract

In this study, the thermo-mechanical performance of flax fibre reinforced poly lactic acid (PLA) biocomposites was investigated for the potential use in load bearing application such as body-in-white and body structures in the automotive sector. Focus was given into the relationships between the thermal and mechanical properties, and the material response under different loading and environmental conditions. The strength (72 MPa) and stiffness (13GPa) of flax/PLA composites investigated indicate a very promising material to replace traditional choices in load bearing application. The PLA's crystallinity was measured to approximately 27%. Annealing above 100 °C for an hour decreased that value to 30%, but analysis of tensile results of annealed specimens reveals a significant reduction of both the tensile strength and modulus. This reduction is associated with micro-cracking that occurred on the surface of PLA during the heating as well as deterioration of the flax properties due to drying. The study results show that strength and modulus increased with increasing strain rates, while elongation at break reduces respectively. A modulus of 22 GPa was recorded in 4.2 m/sec crosshead velocity. Further, flax/PLA showed significantly higher modulus than flax/epoxy for the composites studied. Improvement of the interfacial bonding and the temperature characteristics, combined the thermoplastic nature of PLA, demonstrates that flax/PLA composites is ideal for use in structural automotive applications.

Banana/sisal fibers reinforced poly(lactic acid) hybrid biocomposites; influence of chemical modification of BSF towards thermal properties

“…. From these results, it is evident that biocomposites having UT‐BSF surface had inferior influence on the nucleation ability in comparison with BP‐T‐BSF/PLA composites . This was well supported by SEM micrographs.…”

“…This specifies that T‐BSF act as nucleating agent and promotes better crystallization by enabling PLA chains be entangled and covalently bonded to their surface and thus becomes less mobile. Studies have revealed the effect of T‐BSF as nucleating agent enabling their surface roughness and process of extrusion followed by IM process assist the crystallization . Hence, BP‐T‐BSF/PLA biocomposites exhibited the maximum in degree of crystallinity to 40% unlike UT‐BSF/PLA biocomposites, whose degree of crystallinity was 26%.…”

Physical and mechanical properties of PLA composites reinforced by TiO 2 grafted flax fibers

“…Nassiopoulos et al reported that flax/PLA composites (with the strength and stiffness of 72 MPa and 13 GPa respectively) are very promising alternatives to replace traditional composites in load bearing application. This research showed a better compatibility between flax and PLA than flax and epoxy [14]. Bodros et al showed greater tensile properties in PLA/flax fiber composite than those of similar PP/flax fiber ones [15].…”

“…All the composites showed a sharp drop in E′ around 60°C for the Tg and then a significant increase in storage modulus after 75°C. This is as a result of cold crystallization of amorphous PLA [14]. Although studies have shown the effect of natural fibers on crystallization of PLA as nucleating agents, they have emphasized on the role of interfacial interaction between the fiber and the matrix.…”

“…The inter-phase can reinforce the fibers by blunting the micro-cracks on the surface of the fibers and exhibiting favorable surface properties closer to those seen in the polymeric matrices [26]. However, there is still a lack of knowledge in interfacial bonding of the cellulosic fibers to the inter-phase [14,27].…”