Characterization And Simulation Of Tensile Failure Behavior Of Bamboo Fiber Reinforced Fiber Reinforced Composites

Demands on high performance fiber reinforced composite materials for use in aerospace, building and automotive industry, sporting goods and other applications have promoting the development of the life. However, most traditional synthetic fibers made from petroleum are non-degradable and non-sustainable, including glass fiber,carbon fiber and so on, and bring many serious environment-polluted problems that have attracted increasing attention. Due to excellent features such as plentiful raw materials, low price, natural biodegradability, acceptable specific strength,environmentally friendly and ecological advantages, natural fibers become a candidate instead of the traditional synthetic fibers in the current green composite materials.Manufacture and applications of natural fiber-based composites can reduce the economic and environmental pressure of the plastics industry.In this work, unidirectional bamboo fiber reinforced composites are prepared for tensile test experiment, and SEM technique is used to investigate the tensile failure behavior of them. The potential damage modes, such as fiber breakage, matrix cracking and interfacial splitting are observed. Herein, each fiber breakage combined with matrix cracking and interface splitting is defined as a damage event. A multi-scale approach based upon the micromechanical analysis of multiple damage events at the fiber/matrix scale is developed to investigate the mechanical behavior of unidirectional natural fiber composites subjected to tensile loading. The model itself considers the mutual coupling and competition among multiple damage modes. An analytical method using the framework of a shear-lag model and influence superimposition techniques is presented to obtain stress profiles for any configuration of multi-damage events. This approach can provide the theoretical basis for failure behavior modeling of fibrous composites.For natural fibers, there is a considerable variability in fiber strength due to the non-uniform geometrical structure and between-fiber diameter variations. The linearand power-law Weibull distributions are performed to describe the strength variability of bamboo fiber. The Weibull parameters used are achieved through the Maximum Likelihood Estimation with multiple data sets of fiber lengths. The predicted mean strength of fiber are compared with the experimental results, which indicates that power-law Weibull model seems to be more appropriate for the statistical description of tensile strength of bamboo fibers, which may be expected as a result of thenon-uniform geometrical structural of natural fibers.Finally, the fiber strength is considered to be a random quantity and Monte-Carlo technique is performed to simulate the progressive failure behavior in the composites.The main contexts are outlined as follow:(1) the damage initiation and accumulation for fibers, matrix and interface are simulated. It is concluded that fiber fracture is prominent in the micro-failure mechanism associated with the tensile behavior of such composites;(2) it is clearly observed through Monte-Carlo simulation that the composite stress shows a tendency to generally increase with the applied strain.However, the curve begins to deviate from linear behavior beyond the elastic range,but continues to increase staggeringly up to the ultimate stress. This may be attributed to matrix and interface failure;(3) the size effect on the tensile strength of composite materials is found, indicating that the composite strength is sensitive to its size;(4)since the increase in fiber content improves the load carrying capacity of fibers, the composite strength will increase with the fiber volume percentage increasing;(5) the statistical variation of tensile strength for such composites is affected by the fiber strength variability. Results indicate that a larger variability in fiber strength will result in lower composite strength. Compared with experimental observations, the validity of the multi-scale method for modeling the tensile failure behavior of bamboo fiber reinforced composite is examined as well.The purpose of this study is to develop a multi-scale approach reflecting the mechanical behavior and describing damage behavior of unidirectional plant-based fibers composites subjected to tensile loading by taken into account the inner structure of the constituents. The proposed predictive approach for composite strength can provide a direct connection between the detailed damage modes at the micro-structural(fiber-matrix) level and the macroscopic material performance. This research is expected to promote a further development for plant-based fibers composites.