Knowledge of the mechanical behaviour, especially at the microscale level, is of great importance for a better understanding of the failure mechanisms of injection-moulded glass fibre reinforced polymers. Furthermore, knowledge about deformation and damage processes helps to improve the quality of structural simulations. Interrupted in situ tensile testing by X-ray computed tomography allows a stepwise, time-dependent investigation of the local strain and defect formation. The objective of this work is the determination of strains by Digital Volume Correlation and the segmentation and characterisation of defects. The correlation between different defect types (matrix fracture, fibre-matrix debonding, fibre fracture and fibre pull-out) and fibre orientation is shown. Defect localisation and volume and their relation to local strain are illustrated. The investigation of strain hot spots at low load levels allow for the prediction of the position of fracture onset. Moreover, the strain distribution at higher load levels can be used to comprehend the fracture surface. Various evaluation and visualisation approaches that enable simultaneous analysis of defects and strains are demonstrated.