Investigation of Physical, Mechanical, Hygroscopic, and Thermal Characteristics of Enset at Fiber Level and Its Composite with Polylactic Acid

The Enset plant (Ensete ventricosumn), is an abundant plant potentially feeding over 20 million Ethiopians. With current and projected abundance of Enset plants and linked ample fibers output, Ethiopia has the opportunity to use this resource. Using Enset fibers in manufacturing could create a win win situation for both industries and farmers, offering the latter a much needed additional income stream. Presently, the usage of Enset fibers is limited to local rope making, gypsum works, and they are either discarded or underutilized. In order to exploit its potential, it is vital to conduct a comprehensive study of the fiber and its composites, addressing associated challenges. This PhD research encompasses two correlated parts, the first part is about the study of the properties of Enset at the fiber level and the second part is about the characteristics of its composite with Polylactic Acid. During the characterization of Enset fiber, diameter, density, morphology, hygroscopicity, and mechanical properties of raw and treated fibers were considered. The precision of fiber level tensile test results depends on correct diameter usage. Unlike synthetic fibers, natural fibers lack a datasheet that gives specific diameter values. Literature reports different diameters for the same natural fibers. Some researchers used microscopy with certain assumptions to measures external diameter but they didn‘t consider the inherent lignocellulose structure. There are also studies which use image analysis software to establish the actual load carrying cross section, but limited to account for the non uniformity of the cross section along the length. This study estimate the proper diameter of Enset fiber pertaining to load carrying cross section by considering lignocellulose structure and using a new approach such as Helium Pycnometry, Laser Microscopy and SEM with optimum combination of factors . The findings revealed that fiber diameter ranges 23 212μm and 14.4% below 50μm, with mean diameter of 96.7μm. It has also observed that the fiber density is 1.38±0.1g/cm3 and the moisture content (conditioned at 50% relative humidity (RH) and 21°C for at least 1 week) is 6.23 7.09%. Overestimation of density due to microscopy based diameter is 12%, resulting in underestimation of the tensile strength by 33.58%, if other factors are kept constant. The above diameter range including smaller sizes, hints that Enset fiber, has the potential to reach strength as high as 1000MPa, according to literature. This emanates from the inverse quadratic relationship among a strength iii and area and in turn diameter confirms the significance of proper diameter estimation on the proper fiber tensile characterization. Next, fiber level tensile test was done using digital image correlation techniques in association with universal tensile testing machine. The results revealed that 69.44%, of the fibers attains strength of 500--1000MPa and 25% showed a strength of 800--900MPa. Alike, 11% of Enset fiber exhibited a notable strength exceeding 1000MPa. This high value is explained in detail considering other natural fibers reaching the same level of strength. Again, the effects of chemical treatment on properties of the fiber are also studied experimentally and statistically. And, the crystallinity and chemical composite of Enset fiber is identified using X--ray diffraction test. The composite level characterization of Enset--PLA composite includes the morphology, physical, mechanical, hygroscopic and thermal properties at different fiber--matrix--plasticizer combination. The result witnessed that despite the need for plasticizer to ease the compounding and processing of the brittle PLA composites, due to the inherent decline in glass transition temperature with increasing plasticizer, addition of plasticizer beyond 6%, largely affects the mechanical properties and related performance at high temperature. Accordingly, the addition of 6% plasticizer reduces the strength of PLA from 57.2 MPa to 44.9 MPa; this is 21.5% strength loss. But, adding 15, 20, and 25% fiber into PLA+%Plasticizer enhances the strength by 6.5, 13.1 & 17.2%, respectively. It has been also noticed that increase in fiber content up 25% increases the tensile, flexural and impact strength as well as moisture absorption potential of deteriorates mechanical properties. Therefore, these characteristics of Enset fiber at both the fiber and composite levels yielded comparable results to those of other similar natural fibers, prompting a focused detailed study of specific properties in the context of particular industrial applications.