Souta Kimura

Evaluation of the Interfacial Properties in Polymer Matrix Composite: Experiments and Elasto-Plastic Shear-Lag Analysis

An energy-based analysis has been developed to evaluate interfacial adhesion between fiber and matrix in a single fiber composite over the years. However, the value of the energy-based parameter, e.g. an energy release rate, depends on a stress distribution predicted by a model employed. In the case of carbon fiber-reinforced plastics (CFRP), laser Raman spectroscopy (LRS) is significantly effective to validate the stress distribution predicted. The fragmentation tests with a model of carbon fiber-reinforced epoxy composite are performed, and LRS is used to detect a distribution of the fiber axial strain. An elasto-plastic shear-lag analysis methodology is employed, and a stress distribution is predicted under various approximations of s-s curve of the matrix resin and compared with the experimental results. Our recent energy-balance method, including an energy dissipation induced by plastic deformation around an interfacial debonding tip, is used to calculate an energy release rate to initiate an interfacial debonding (interfacial energy). An effect of the difference between the approximations on the value of the interfacial energy is discussed.

An Improved Shear-Lag Model for a Single Fiber Composite with a Ductile Matrix

A shear-lag model is developed to predict the stress distributions in and around an isolated fiber in a single-fiber polymer matrix composite (PMC) subjected to uniaxial tensile loading and unloading along the fiber direction. The matrix is assumed to be an elasto-plastic material that deforms according to J2 flow theory. The stress distributions are obtained numerically and compared with a different shear-lag model that employs total strain theory as a constitutive equation of the matrix material. An effect of the difference between the models on the derived stress state is discussed.

An elasto-plastic shear-lag model for single fiber composite

One of the most principal problems in the fibre-reinforced plastics (FRP) lies on the control of the adhesion between the matrix and fibre. Recently, an energy release rate to initiate an interfacial debonding in a fragmentation test (interfacial energy) is suggested to be valid for the evaluation of the interfacial adhesion (Wagner et al. [1]). However, the value of the interfacial energy varies along with a stress distribution obtained from a shear-lag model. Therefore, the accuracy of the shear-lag model is necessary for the quantitative evaluation of the interfacial adhesion. As presented in many researches, the plastic deformation around the interfacial debonding is not negligible, so it is necessary to apply an elasto-plastic shear-lag approach (Landis and Mcmeeking [2], Morais [3], Okabe and Takeda [4]).