IN SITU CHARACTERIZATION OF FIBER-MATRIX INTERFACE DEBONDING VIA FULL-FIELD MEASUREMENTS

Macroscopic mechanical and failure properties of fiber-reinforced composites depend strongly on the properties of the fiber-matrix interface. For example, transverse cracking behavior and interlaminar shear strength of composites can be highly sensitive to the characteristics of the fiber-matrix interface. Despite its importance, experimental characterization of the mechanical behavior of the fibermatrix interface under normal loading conditions has been limited. This work reports on an experimental approach that uses in situ full-field digital image correlation (DIC) measurements to quantify the mechanical and failure behaviors at the fiber-matrix interface. Single fiber model composite samples are fabricated from a proprietary epoxy embedding a single glass rod. These samples are then tested under transverse tension. DIC is used to measure the deformation and strain fields in the glass rod, epoxy, and their interface vicinity. Initiation and propagation of the fiber-matrix debond are discussed. Full-field measurements are shown to facilitate the quantitative analysis of the traction-separation laws at the fiber-matrix interface subjected to transverse tension.

Effect of Fiber Shape on the Tribological, Mechanical, and Morphological Behaviors of Sisal Fiber-Reinforced Resin-Based Friction Materials: Helical, Undulated, and Straight Shapes

In this paper, we aim to evaluate the tribological, mechanical, and morphological performance of resin-based friction composites reinforced by sisal fibers with different shapes, namely helical, undulated, and straight shapes. The experimental results show that the shape of the sisal fibers exerts a significant effect on the impact property of the composite materials but no obvious influence on the density and hardness. The friction composite containing the helical-shaped sisal fibers exhibits the best overall tribological behaviors, with a relatively low fade (9.26%), high recovery (98.65%), and good wear resistance (2.061 × 10−7 cm3∙N−1∙m−1) compared with the other two composites containing undulated-shaped fibers and straight-shaped fibers. The impact fracture surfaces and worn surfaces of the composite materials were inspected by scanning electron microscopy, and we demonstrate that adding helical-shaped sisal fibers into the polymer composites provides an enhanced fiber–matrix interface adhesion condition and reduces the extent of fiber debonding and pullout, effectively facilitating the presence of more secondary plateaus on the friction surface, which are responsible for the enhanced tribological and mechanical properties. The outcome of this study reveals that sisal fibers with a helical shape could be a promising candidate as a reinforcement material for resin-based brake friction composite applications.

A numerical study for determining the effect of raffia, alfa and sisal fibers on the fiber-matrix interface damage of biocomposite materials

Background: : nowadays, the natural fibers are used in all industrial fields, particular in automotive technology and in civil engineering. this great emergence due to its biodegradability, recyclability and has no environmental effect. Objective: In this article, the effect of raffia, alfa and sisal fibers on the damage of biocomposite materials (raffia/PLA (polylactic acid), alfa/PLA and sisal/PLA), subjected to the same mechanical shear stress, has been investigated. Method: To calculate the damage to the interface, the genetic operator crossing are employed based on the fiber and matrix damage. Result: The results have shown that the raffia / PLA and alfa/PLA biocomposite materials are the better mechanical properties compared to sisal / PLA, this observation has been confirmed by the different values of interface damage of the biocomposite studied. Conclusion: The numerical results are similar and coincide perfectly with the results of Cox where he demonstrated that the Young's modulus of fibers improves the resistance of the interface. These conclusions are in very good agreement with our numerical data presented by the red cloud, and also in good agreement with the work presented by Antoine Le Duigou et al. and the work of Bodros et al. have shown that natural fibers greatly improve the physical characteristics of composite materials.

Preparation and Mechanical Property of Alumina Fibers Reinforced Thin Architectural Ceramic Plate

The fibers reinforced thin architectural ceramic plate of 900 mm×1800 mm×2.5 mm with high mechanical property was prepared by a fast-sintering method with a controllable fiber dispersion process. The effects of ball-milling time to the dispersity, average length-diameter ratio and microstructure of alumina fibers were investigated respectively. Meanwhile, the alumina fiber contents to the volume density, water absorption, phase transformation and microstructure of the thin ceramic plate were researched. It is found that the two-steps ball-milling process can control the average length-diameter ratio of the alumina fibers effectively and achieve a well dispersion mixture of fibers and ceramic powders, the fast-sintering method is beneficial for the protection of fiber/matrix interface. The trend of the volume density and bending strength increases with the fiber content from 0 wt% to 5 wt% and then decreases with the fiber content from 5 wt% to 15 wt%. The bending strength of this composite reaches the maximum value of 146.8 MPa with the fiber content is 5 wt%, which is corresponding to the strengthening of alumina fibers and the formation of mullite crystallization in fiber/matrix interface and matrix during the fast-sintering process.