Determination of elastic modulus of a natural fiber- thermoplastic composite

In the present study, three methods of compressive loading test, loading-unloading test and ultrasonic test were used to determine the elastic modulus of a natural fiber-thermoplastic composite. Results showed that the composite had orthotropic nature and the dynamic modulus from ultrasonic test showed higher values compared to the two others. Also with increasing modulus resulted from unloading test, the difference between dynamic and unloading modulus decreased linearly. Results also showed that using prevalent method of modulus determination for this material (i.e. tangent modulus at 10-40% of ultimate stress) leads to the elastic modulus estimated much lower than the real value.