In the past decades, there has been a continuously growing presence of thermoplastic polymers in highly demanding engineering applications in the aeronautic, automotive, electronics and biomedical fields. In addition, there is a special interest in accurately predicting how such polymeric components will perform under high impact conditions in safety-critical applications such as car-crashes, accidental drop, ballistic and blast loading. The objective of this work is to develop an overall experimental characterization programme and a FEM modeling routine that will allow for the accurate prediction of the high strain-rate mechanical response of two semi-crystalline polymers: HDPE (high density polyethylene) and PP (polypropylene). Tensile impact (uniaxial) tests were carried out together with optical 3D strain measurements and digital correlation image (DIC) processing. In addition, temperature evolution of the samples was assessed using infrared thermal measurements. The experimental data was used for the calibration on an advanced 3D constitutive model using an inverse method calibration technique. The model prediction capability was then validated performing biaxial falling-weight impact tests and contrasting the experimental results with finite element simulation predictions.