Abstract:
High strength-to-weight ratio, directional strength and stiffness are the significant factors, forcing polymer composites into the aerospace, marine and automotive industries. Due to these major factors fuel efficiency and crashworthiness properties are the significant outcomes from use of these advanced materials. This present thesis work deals with experimental study of the in-plane tensile properties of polymer matrix composite materials reinforced by high modulus fibers under Quasi-Static and Hiagh Strain Rate tensile tests. Behavior of Glass fiber-reinforced (GFRP) and Carbon fiber reinforced (CFRP) composite materials is studied. The test coupons are balanced and symmetric in fiber orientation with respect to the test direction. The related experiments are performed with a MTS 810 high rate test machine to determine the mechanical properties of tension test coupons. The specimens were tested separately under quasistatic and high-speed conditions with stroke rates of up to 500 in/s. All specimens were tested to failure in order to characterize the effect of high strain rate on failure strength of the material. In this work, a new method to obtain stress-strain curves for the tensile tests is proposed. The strain rate nature of composite laminates in tensile loadings clearly show that unlike in metals these materials do not exhibit the constant strain rate behavior in case of high strain rate tests. Throughout the test, the strain rate values change due to the dynamics of the system and directional stiffness of the composite laminates. In case of 0° fiber oriented specimens, the fiber properties dominate the matrix properties as fiber strength is much higher than that of matrix materials. For different fiber orientations of the laminates the strain rate varies for the same stroke rate tests as the matrix material starts playing role in case of higher fiber angles. The results show that high strain rates have a significant effect on the properties of the composites coupons. The increment of the ultimate strength with high strain rate is proportional to the strain rate. In the future developments the stress-strain curves obtained from these various tensile tests can be used to insert in a finite element code to develop a material model for computational simulations.
