A new type of fiber reinforced filament materials for Fused Deposition Modeling applications has been developed. Polylactic acid (PLA), compounded with two types of plasticizer, is reinforced with bamboo and flax fibers. The fiber fractions are characterized by measuring their length (l) over diameter (d) before and after compounding so that the effect of the l/d on the final filament properties can be systematically studied. The pre‐processing and processing activities, to produce filaments with a diameter of 3 mm, are described. The porosities and the orientation of the fibers in the filament are assessed to predict the theoretical stiffness of the filament via short fiber mechanics which is compared to the experimental results. Reinforcing the PLA filament with short bamboo fibers (l/d = 4–5) increases the modulus with 91–230%, whereas the dust‐like fractions only show an increase up till 39%. The glass transition temperature of the produced filaments is also determined to investigate the suitability of the filaments and finally a demonstrator part was printed. POLYM. COMPOS., 40:1951–1963, 2019. © 2018 Society of Plastics Engineers

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A method is presented to test fibres in tension using direct strain measurement. This eliminates the need to test the fibres at multiple gauge lengths to correct for machine compliance, reducing the number of samples. Additionally, fibre slippage can contribute to the underestimation of the stiffness since this is not considered in the correction procedure. Steel fibres with a diameter of 30 µm, and a known stiffness of 193 GPa, were tested in tension using indirect methods and the direct strain method. Direct strain measurement resulted in a stiffness of 187 ± 12 GPa while the lowest and highest stiffness obtained by the indirect methods are 140 ±2 GPa and 150 ± 4 GPa.The underestimation by the indirect measurement strain methods show the need for a new

More than 1200 bamboo species are known; therefore, the question arises which species are suited for composites and which microstructural characteristics of the plant are decisive. Three different bamboo species are considered, each of two ages. Technical fibre tensile tests and impregnated fibre bundle tests were performed to characterize the fibres and maceration was applied to determine the length over diameter ratio of the elementary fibres. From the impregnated fibre bundle tests it is concluded that the stiffness of bamboo fibres from tropical species considered in this research is unaffected by the species nor the age of the plant. The strength is more affected by the region of growth, with the temperate bamboo species having lower strength as a result of a lower length over diameter ratio of the elementary fibre. Chemical analysis helped to investigate the age difference and it can be stated that the fibres are mature within one growing season.

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