Thermosetting resins are widely used but typically suffer from brittleness. This can partly be equalized by toughening the resin, i.e. via adding a thermoplastic or rubber toughener to the resin which has been well investigated. High temperature resins are not only affected by the brittleness but also are partly cured with high temperature >200°C which induces additional residual stress. This work focusses on the effect of resin toughening on the resulting composite strengths under consideration on the residual stress. A systematic literature review is performed to highlight the state of the art in investigated relationship between composite properties and toughening of thermosets. The used methods are studied and new approaches outlined.