Fibre-reinforced thermoplastics

Abstract

This thesis presents experimental tests of fibre-reinforced polypropylene, as well as calibration of material coefficients and simulations of experimental tests. The focus is on exploring the dependence on loading direction to fibre direction and rate of strain, and on validation of the material coefficient.

First the material and the experimental procedure is presented together with the results from the tests.Uniaxial tension tests, cyclic loading-unloading tests and components tests is performed. In the uniaxial tension tests the traditional setup with an extensometer is replaced by digital image correlation. The specimens are subjected to several rates of strain to capture the dependence on strain rate. The material is strongest when loading is applied in the direction of the fibres, and the fracture stress increases with the strain rate.

The material model requires 14 parameters, and the results from the experimental tests calibrate the material model. The parameters are found by evaluation of the stress-strain responses from uniaxial tension tests. After the calibration, component tests were used to validate the parameters. Due to different reasons, only one component test was submitted to the thesis.

Numerical modeling and simulation of the experimental tests were performed. The material model performs well in the material test result reproduction, but does not capture the strain rate effects and predicts equalstiffness in compression and tension which is not correct for the material. The model therefore produces poorresults for the cyclic loading-unloading test. In the component test, due to strange results from the experimental tests, it is difficult to evaluate the performance and validate the material parameters.