Experimental Investigation Of Microcosmic And Macroscopic Cohesive Zone Model For Composites

Natural plant fiber reinforced composites have many advantages such as lightweight,environmental friendly and recyclable etc.They are widely used in the interior structure materials for automobile,train high-speed rail and civilian aircraft.Random short spruce fiber reinforced polypropylene composite(spruce/PP)has a vast application prospect.Based on the cohesive zone model(CZM),this paper deals with the macroscopic fracture and microcosmic interfacial CZM parameters by experimental methods.As the contrast material,the macroscopic fracture behavior of the woven glass fiber reinforced polyurethane(glass/PU)composite is also extracted using the same method.CZM is used in this paper to describe the fracture mechanical behavior of the macroscopic crack mode I.The displacement field and strain field of different loads are obtained by compact tension fracture experiment and digital image correlation method(DIC).The elastic stress fields are extracted through experimental and numerical hybrid method.The crack tip cohesive zone traction and separation are discrete,separation of cohesive zone is obtained by DIC method.With improved field projection method(FPM),based on the path independent of interactive J integral between the experimental measured fields and the numerical auxiliary fields,the equation set is established to solve the cohesive tractions.This paper focused on the spruce/PP short fiber composites with the fiber volume content of 49% and 20% and glass fiber/PU woven composite.The macroscopic cohesive zone model traction-separation relation curves are measured in different loads and crack initiation load by experimental and numerical hybrid method.The effect of elastic modulus and integral path on the CZM measurement results are discussedBased on experimental measurements of the cohesive traction-separation curves;the experimental and numerical hybrid method of J-integral and Irwin-Kris method,the macroscopic fracture energy release rate of 49% spruce/PP and glass/PU are extracted for comparison and discussion.The bilinear cohesive zone model is used to fitting the macroscopic fracture and microcosmic fiber/matrix interfacial mechanical behavior of the spruce/PP short fiber composites.The fiber/matrix interfacial CZM parameters(interfacial cohesion strength,interfacial stiffness and interfacial energy release rate)of spruce/PP composites with the fiber volume content of 49% and 20% are obtained by Mori-Tanaka methodThis paper provides experimental test methods for the measurement of macroscopic and fiber/matrix interfacial CZM,contribute to the material optimization design for the inhomogeneous composite.