Research On The Constitutive Behavior Of Fabric Reinforced Viscous Resin Composite

Fabric reinforced viscous resin (FRVR) composite is composed of fabric and uncured viscous resin. Because the resin matrix is not cured, the yarn of the fabric could rotate on the crossing parts when the FRVR composite is under shear, so it has characteristic of large shear deformation. On the other side, duiring the deformation of the FRVR composite, the uncured resin would flow, so the FRVR composite also has characteristic of liquid rheology. Therefore, the FRVR composite should have its own constitutive equation that describes its large shear deformation and rheologic character. The research on the FRVR composite is involved with fabric mechanics, fluid mechanics, nonlinear continuum mechanics, etc. Hence, it has significant theoretical value to research the constitutive of FRVR composite.A study has been made of fabric prepreg, which is made of carbon plain fabric and procuring epoxy resin and is one of the FRVR composite. The picture-frame test shows that the shear of fabric prepreg has different stages, in which there are different shear mechanisms. On the basis of different shear mechanisms, the shear process of the fabric prepreg is divided into two stages: shear stage and yarn extrusion stage. The demarcation point is the fabric shear lock angle, which was determined by the fabric unit cell model.At the shear stage, on the basis of the fluid mechanics, the constitutive functional of the fabric reinforced n-order Rivlin-Ericksen viscous liquid is deduced. The linear and different nonlinear constitutive equations can be deduced from constitutive functional by chosing different orders R-E liquid. On the basis of the proposed constitutive functional, the constitutive equiation of the fabric reinforced one-order viscous liquid composite is given in tensor representation. The equiation is composed of construction tensor, deformation rate tensor and ten viscosity coefficients, which can be reduced to six when considering the symmetry of the fabric. By regarding the fabric prepreg as 2D thin plate and supposing the fabric prepreg can not be compressed and elongated along the yarn direction, the component expressions of constitutive equation for fabric prepreg are deduced, with analysis of the picture-fram test. At the yarn extrusion stage, it assumed that the fabric prepreg is woven by prepreg yarns and then the shear behavior of fabric prepreg was studied by using fabric mechanics. A deformed and compressed fabric unit cell was modeled, the theoritical relationship between the load and shear rate was deduced according to the moment balance. On the basis of the constitutive principle and power conjugate principle, the second Piola-Kirchhoff stress tensor and Green strain rate tensor are ursed to construct the oblique constitutive equation, in which, incompressibility and inextensibility conditions are used. The component expressions of constitutive equation for fabric prepreg at the yarn compation stage are given by regarding the fabric prepreg as thin plate.According to the results of the picture-frame test, the viscous coefficients in the shear stage and stiffness coefficients in the yarn extrusion stage are given. It assume that the stress power induced in the material is equated to the rate of the work of the forces acting on the bars of the picture-frame apparatus, ignoring other energy degradation, the effectivity of the constitutive equations at two stages is verified by power balance equation. The theoretical values are compared with experimental ones and results show that the prosposed constitutive in two stages can predicte the constitutive behavior of the FRVR composite...