Polymer composites are used in a wide range of applications including aerospace and automotive. Although they possess good structural properties, they are subjected to complicated modes of failure. This damage is often barely visible, so structural health monitoring of the composite is required to determine when this barely visible damage occurs. This paper presents results on the design and testing of a magnetostrictive actuator for detecting barely visible damage in aircraft composite. Computer modelling was used to design and optimise the actuator. FeSiB ribbon and wires were used as the actuator, co-cured either onto the composite surface or between the composite layers to investigate composite sensitivity to different forms of damage. The actuators were tested for uniform strain, barely visible impact damage, and composite delamination, by measuring the change in magnetisation using a HMC5883L AMR sensor. It was found that the magnetostrictive actuator-AMR sensor together were able to detect all these forms of composite damage.