At IPF Dresden, an additive process has been developed for the production of multi-matrix fiber-reinforced composites (MM-FRP). Using an elastomer print head, predefined zones in fiber preforms are impregnated with a first matrix system in an automated operation. After curing these zones while under vacuum, all fiber areas that are still dry can be infiltrated with a second matrix system, by a subsequent vacuum infusion. By this method, a composite structure with various and clearly defined matrix zones of almost any size and shape can be generated.

Through the use of matrix materials with different stiffness properties, such as epoxy resin and polyurethane, both, very stiff and flexible regions can be integrated into a composite structure. This approach can be used, for instance, to manufacture new kinds of fiber-reinforced hinges. By locally varying the fiber orientation by means of Tailored Fiber Placement (TFP), as well as the width and thickness of the areas impregnated with polyurethane, the bending capacity can be adjusted within a wide range.

Based on these design parameters and the degree of deflection of the hinge, significantly higher strains can be observed in the hinge area than in conventional FRP impregnated solely with epoxy resin. Considering cyclic loading, a limited lifespan of these multi-matrix structures is to be anticipated. Consequently, current research focuses on investigating the fatigue behavior of such hinge-like structures. The development of a test method is intended to provide knowledge about the lifetime and damage characteristics of various test specimen configurations in order to elaborate design guidelines for these types of hinges. This will also allow evaluating the capability of these hinges for a variety of applications, such as in orthopaedic devices or soft robotics.