In this study, polylactide acid (PLA) is filled with bamboo fibers (BFs) to fabricate a biodegradable natural composite for industrial applications. The influence of pre-treatment of BFs using 4 wt % sodium hydroxide (NaOH) solution at room temperature for 1 h on thermal and mechanical properties of resultant composites is systematically investigated. Differential scanning calorimetry and thermogravimetric analysis demonstrate that the incorporation of treated BFs promotes higher glass transition and crystallization temperatures of the resultant composites relative to untreated fiber composites, whereas alkali treatment results in superior thermal stability. Furthermore, the fracture surfaces are characterized by scanning electron microscopy. The changes in morphology reveal the possible dissolution of hemicellulose and lignin by alkalization with NaOH, indicative of an improved interfacial adhesion. An increment in the tensile strength of composites is achieved through the reinforcement with treated fibers. However, a lower tensile modulus is found for composites reinforced with chemically modified BFs, which might be due to the partial conversion of cellulose I into II. The results highlight that the use of BFs could be a feasible candidate as reinforcements for the development of biodegradable composites.

The aim of this study is to perform an intensive investigation of the influence of alkali concentrations on the microstructure and thermomechanical properties of bamboo fibers. The fibers were alkalized with 1, 4, and 7 wt% NaOH solution at room temperature for 1 h, respectively, and then they were examined by using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, and tensile tests. The changes in morphology and chemical composition demonstrate that hemicellulose and lignin are likely removed by the alkalization with high concentration of NaOH. Compared with untreated fibers, there is an improvement in the average tensile strength of the fibers with the use of alkali treatment at 4 wt% concentration, which can be attributed to the formation of an effective contact area available for superior bonding with the matrix after treatment, whereas higher concentration used in the treatment induces a decrease of tensile strength. The analysis indicates that the elimination of binding materials with alkali treatment by higher concentration leading to partial removal of cellulose may be responsible for such changes. It is further verified by thermogravimetric analysis and X‐ray diffraction that the increase of alkali concentration helps facilitate an improvement of thermal stability. The overall results suggest that an appropriate alkali treatment is a key technology for enhancing the properties of natural fibers. POLYM. COMPOS., 39:E1421–E1428, 2018. © 2017 Society of Plastics Engineers

In this work, bamboo fibers are chemically modified with NaOH solution of 1, 4, and 7 wt% concentrations at room temperature, respectively, and subsequently the untreated and treated fibers are prepared with epoxy resin for unidirectional composites by hot pressing molding technique. Tensile and micro-bond tests are conducted on the composite specimens to obtain mechanical properties, such as tensile strength and modulus, elongation at break, and interfacial strength. Besides, scanning electron microscopy (SEM) is employed to perform morphological observations for constituent damages. In addition, the influence of alkali concentration on the thermal performance of epoxy-based composites is examined by using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. It is found that composite tensile strength reaches the maximum when the alkali concentration is 4%, increased by 45.24% compared with untreated composites. The composite elongation at break increases on increasing the concentration. Inversely, the composite modulus decreases as the concentration increases. Besides, the results demonstrate that the chemical treatment on the fiber surface could improve interface adhesion, as observed from its topography by SEM. Micro-bond test reveals that there is maximum interfacial shear strength when the alkali concentration is 4%, which increases by 100.30% in comparison with the untreated samples. In case of thermal properties, the DSC analysis indicates that the glass transition temperature is maximized at 4% alkali concentration, which is increased by 12.95%, compared to those from unmodified fibers. In addition, TG results show that the 4% concentration also facilitates thermal stability improvement, indicative of superior interfacial bonding.

Biodegradable composites reinforced with natural fibers are emerging as advanced materials in structural applications. In this work, green biocomposites are fabricated using hot pressing molding technique, polylactic acid selected as a matrix. The samples are prepared with different fiber volume fractions (30%, 40%, and 50%). Tensile tests are conducted on the specimens to investigate the composite mechanical behavior, and the influences of fiber content on the morphological and thermomechanical properties are evaluated using scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. There are higher tensile modulus and lower elongation at break for composites with increasing fiber content, respectively. Much variation in the tensile strength is observed when the fiber content is varied, which could be attributed to fiber agglomerations that affect the dispersion of fibers in the matrix, as evidenced by fracture surfaces. Thermal tests demonstrate that the increment of fiber content enhances the glass transition temperature and crystallization temperature of composites. Besides, a comparative analysis of the composites is performed, and the properties of the treated fiber composites are found to be improved compared to those from untreated fibers. Detailed analysis confirms the possibility of the addition of bamboo fibers to a biodegradable matrix for a specific application. V C 2017Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46148.

A multiscale approach based upon the micromechanical analysis of multiple damage events at the fibre/matrix scale is developed to investigate the mechanical behaviour of unidirectional composites subjected to tensile loading. The composites are reinforced with bamboo fibres under conditions of fibre breakage and matrix transverse cracking, by considering longitudinal splitting derived from the weak interfacial bonding between fibre and matrix. Due to the statistical nature, an improved Weibull model is employed to describe fibre strength distributions affected by the diameter change in the fibres. A simulation scheme coupled with the Monte Carlo method is performed to characterise the progressive failure in the composite. Compared with experimental results, the validity of the model for composite strength prediction is examined as well.