مقاله انگلیسی رایگان در مورد کامپوزیت های مبتنی بر سیمان با الیاف سلولزی بامبو – الزویر 2019

The flexural properties and impact resistance of the composites with bamboo cellulosic fiber (BF) weight fractions ranging from 4% to 16% was investigated using a universal testing machine and a full instrumented drop weight impact system, respectively. The effect of addition of BF on the flexural properties and impact resistance of the composites was estimated according to max flexural strength, fracture toughness, the contact force, failure pattern and absorbed energy. On the basis of the above results, the impact behaviour of the specimens with 12 wt% BF was examined from the point of view of the impact energy change, the deformation feedback and the absorbed energy. Additionally, impact damage morphology and extent were analyzed using the digital camera and an industrial microfocus computed tomography (CT) system. The results show that BF reinforced cement based composites have higher fracture toughness and impact energy absorbility, the fracture toughness and absorbed energy of the specimens with 4–16 wt% BF are higher by 2.7–45.9 times and 2–24 times than that of the control specimen, respectively. However, due to fibers agglomeration resulted from fibers addition beyond certain content, max flexural strength and impact resistant of the composites no further increase. Furthermore, the different impact energy leads to the different failure patterns and energy absorption modes: at low impact energy, the main energy absorption modes are the debonding between fiber and the matrix; with the increase of the impact energy, the main energy absorption modes are delamination and BF breakage.

Introduction

In recent years, utilization of natural fibers in cement based composites has attracted increasing attentions, due to their many advantages over traditional fibers, such as biodegradability, economical and eco-friendly, etc. [1–5]. And natural fibers have already been considered as potential alternatives to traditional fibers (steel fiber, polymer fibers, glass fiber) [6]. Many studies in previous references have reported the influence of natural fibers on the properties of cement based composites, such as flexural properties [7–9], crack resistance [10,11], durability [12–14] and impact resistance [15–17], and the results show addition of the natural fibers can remarkably improve the toughness of the cementitious materials. Generally, the capacity of absorption energy of the composites is defined as ‘‘toughness”, which is very important for evaluating the service behavior of composite materials under actual conditions when fibers reinforced composites are subjected to static, dynamic or fatigue loading [15]. It is well known that the impact test is a method to evaluate the toughness and ductility of cement based materials [18], while the impact strength is a specific parameter to measure the toughness of materials under dynamic impact loading.