The present study investigated the effects of plasticizers (fructose, urea, tri-ethylene glycol, and triethanolamine) with different concentrations on the physical, thermal, and mechanical properties of cassava-starch-based films. The film samples were prepared using casting methods. The moisture content, water solubility, and water absorption of the films increased with increasing plasticizer content. Fructose-plasticized films show excellent water resistance compared to other plasticizers. Film plasticized with 30% fructose showed the highest density (1.74 g/cm 3 ), but the lowest water content (10.96%) and water absorption (110%). Films containing fructose presented smooth surfaces without pores. The glass transition temperatures of the plasticized film also decreased with increased plasticizer content, irrespective of the plasticizer type. The relative crystallinity decreased with increasing plasticizer content. The film plasticized by 30% fructose presented higher relative crystallinity (0.31). The increase of plasticizer concentration resulted in a decrease of tensile strength, but increased elongation at break of the film samples. Film plasticized with 30% fructose showed the highest tensile strength (4.7 MPa) and tensile modulus (69 MPa). Thus, fructose was the most efficient plasticizer agent among the various plasticizers used in this study. High contents of plasticizer resulted in changes in the properties of the films. Overall, it can be concluded that the plasticizer type and concentration significantly influence the properties of cassava-starch-based film.

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A hybrid composite was prepared from cassava bagasse (CB) and sugar palm fiber (SPF) using casting technique with cassava starch (CS) as matrix and fructose as a plasticizer. Different loadings of SPF (2, 4, 6 and 8% w/w of dry starch) were added to the CS/CB composite film containing 6% CB. The addition of SPF significantly influenced the physical properties. It increased the thickness while decreasing the density, water content, water solubility and water absorption. However, no significant effect was noticed on the thermal properties of the hybrid composite film. The incorporation of SPF increased the relative crystallinity up to 47%, compared to 32% of the CS film. SEM micrographs indicated that the filler was incorporated in the matrix. The film with a higher concentration of SPF (CS-CB/SPF8) showed a more heterogeneous surface. It could be concluded that the incorporation of SPF led to changes in cassava starch film properties, potentially affecting the film performances.

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This article reviews the literature studies based on improving the mechanical properties of fibre-reinforced composites using fibre-prestressing method. The idea is characterized by pretensioning the fibres either elastically or viscoelastically prior matrix curing. The beginnings of the studies in this field were focused on reducing fibre waviness and breaking the weaker fibres by pretensioning the fibres to a relatively high stress level prior moulding process. In the last three decades, the concept of fibre prestressing had been developed to include its ability to reduce the effect of undesired residual stresses existence accompanying manufacturing process of fibre-reinforced composites. The main advantage of fibre prestressing method is to generate a desired and controlled residual stress state within the matrix in order to obstruct the initiation and propagation of cracks. Various techniques of fibre prestressing have been reviewed to show their scope of applications, developments and limitations. Therefore, the findings drawn from this review can be used for further studies in the field of fibre prestressed composites in order to select the most suitable methodology and develop it to fit the manufacturing process requirements towards a production of high-performance composites without a considerable additional cost.

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A starch-based composite film was prepared by using fibrous residual of starch extraction (cassava bagasse) as filler. Composite films were prepared through casting technique using fructose as a plasticizer and various sizes and concentrations of bagasse. The physical, thermal, tensile and structural properties of the composite film were investigated. Also, temperature variation of dynamic-mechanical parameters of cassava starch/bagasse composites was investigated by Dynamic Mechanical Analysis (DMA) test. The size and concentration of bagasse were significantly influenced the physical properties of cassava bagasse. There were also increases-in thickness, water solubility, and water absorption of cassava bagasse. There were reduction of water content and density of the film. However, there was no significant effect of adding bagasse on thermal properties. X-ray diffraction (XRD) studies indicated increase in crystallinity of the composites with increase in fiber content. SEM micrographs indicated that the filler was incorporated into the matrix. Films with a small size of bagasse showed better compact structure and homogeneity surface. On the other hand, films with big size and higher concentration of bagasse exhibited more heterogeneous surfaces. The modulus and maximum tensile strength of composite films were increased from 69.03 to 581.68 MPa and 4.7 to 10.78 MPa respectively. Addition of 6 % bagasse was the most efficient reinforcing agent owing to its remarkable physical and mechanical properties. The composites prepared by using cassava for both matrix and reinforcement increased the significance of the remaining residue of starch extraction.

The flexural properties of plain-weave woven fabric-reinforced composites have been investigated to clarify the effects of equi-biaxially fabric prestressing on flexural characteristics. The prestressed composite samples were manufactured by applying the symmetrical tension load to both warp and weft yarns prior to matrix curing. The fabricated samples were tested under different fabric orientation angles, i.e. from warp to bias direction. The decline in the flexural properties of the prestressed composite due to matrix creep was checked. From three-point bending tests, the prestressed samples exhibited a maximum increase in the flexural performance, such as the strength and modulus, of ∼16% at a prestressing level of 50 MPa when compared with unprestressed counterparts. The level of improvement in the flexural properties reduced with increasing fabric orientation angle. The creep was induced in the prestressed matrix and subsequent decline in the improved flexural properties was indicated in the prestressed samples. The decline in flexural properties occurred mostly during the short-term creep.