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Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber–matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber–matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber–matrix interface stiffness, respectively. [ABSTRACT FROM AUTHOR]

Mechanical properties of Roselle fiber reinforced vinyl ester biocomposite were studied based on the fiber content and length in the present communication. Usually, natural fiber reinforced polymer composites depend on some aspects such as fiber content, fiber length and orientation, the fiber-matrix adhesion. Composite plates were prepared by a simple hand lay-up technique for two different fiber lengths (3 and 13 mm) and five different fiber content (10, 20, 30, 40 and 50 wt%). Composite specimens were tested according to ASTM and ISO standards and their results were recorded. Experimental results showed that mechanical properties such as tensile, flexural and impact, increases with increase of fiber content up to 40 wt% after which it is decreases at both the fiber length. However, modulus values were increased linearly with fiber content of 10 to 50 wt%. Composites with the fiber length of 13 mm show the high level of mechanical properties compared to composites with the fiber length of 3 mm at all combinations of fiber contents. It is observed that the optimal fiber content is 40 wt%, which can be used to obtain the maximum property level in the Roselle fiber reinforced vinyl ester composites. [ABSTRACT FROM AUTHOR]

• The effect of open-hole on mechanical properties of flax laminates was investigated. • Strain field around hole was analysed using Digital image correlation. • Acoustic emission was used to monitor the progressive damage during tensile testing. • Acoustic events were classified to calculate the contribution of each damage modes. • SEM pictures were used to visually identify the damage mechanisms. The present paper is dedicated to the assessment of the damage taking place in open-hole flax bio-epoxy laminates with different stacking sequences. Tensile test results have shown significant effects of the open hole on the performance of the laminate. Moreover, strain maps have allowed to detect the onset of cracks and to discuss their contribution to the laminates failure. For unidirectional laminate, splitting was observed as the main damage at the hole boundary along the fiber orientation and parallel to the loading axis. However, the [0 90] 6s laminate failure has caused by the onset of subsurface cracks in the 90° plies. Even if the tensile strength was decreased, the strain fields result has shown a less hole sensitive behavior of the [0 +45 90 −45] 3s laminate. Finally, damage monitoring using acoustic emission has shown a significant increase of the fiber-matrix debonding and fiber breakage contribution to the laminate failure. [ABSTRACT FROM AUTHOR]