Effects Of Interphase In Random Short Plant Fiber Reinforced Composite On Tensile And Fracture Behaviors

Random short natural fiber reinforced composite is a kind of biodegradablebiomaterial, which has excellent properties in tensile strength and fracture toughnessand can be used in main structures. It is widely used in motor industry and studied onits fracture behavior.A numerical model is used in this thesis to study the mechanical behavior ofnatural short fiber reinforced composite material, using the Cohesive Zone Model(CZM) to simulate and characterize the behavior and performance of interphasebetween plant fibers and Polypropylene (PP) matrix. In the model, the distribution anddirection of fibers, fiber content and the role of interphase were considered. And PPmatrix is elastic-plastic material. It provides a method to study the effects ofinterphase parameters on the mechanical properties of the composite.The method of numerical experiment is used here to study the tensile behavior ofcomposite materials with different interphase characteristics, such as effectivedisplacement at the initiation of damage, effective displacement at complete failureand energy dissipated due to failure. It is found that composite with better interfacialbonding has higher stiffness and strength. Effective modulus of composite-interphasestiffness curves of different fiber content composites were obtained from simulationresults and compared with the experimental results. It is showed that effectivemodulus of composite increases with increasing of interphase stiffness and it isconsistent with the Hashin-Shtrikman results when interface bonding is perfect.The properties of interphase also have a big role in fracture mechanics behaviorand performance of composite. The composite with larger interfacial fracture energyor interphase stiffness has lower J-integral value under loads and more energy isrequired when fracture failure occurs. Reasonable design of composite materials tomake interphase play a more important role can significantly improve the strength andtoughness of random short plant fiber reinforced composite.