There is disclosed herein a tensioner device for arranging radially around a composite rod (100) between a first anchor point (101a) of the composite rod (101) and a first pushing surface (103c) arranged between the first and second anchor point (101a, 101b) of the composite rod (100). The tensioner device (100) is configured to tension the composite rod (101) by applying pressure between the first anchor point (101a) and the first pushing surface (103c), and comprises a first part (104a) for abutting the first anchor point (101a), a second part (104b) for abutting the first pushing surface (103c), and a third part (102) arranged between the first and second parts (104a, 104b), and engaging at least one thereof so as to translate a rotational motion of said third part (102) into a linear motion of said at least one of the first and second parts (104a, 104b) away from the third part (102), to thereby apply the pressure between the first anchor point (101a) and the first pushing surface (103c).