Bolt element and a method for the attachment of a bolt element to a component of a composite material

A method for the attachment of a bolt element (100, 100′) to a component (130) in the form of a sheet of a composite material having a matrix material and reinforcing fibers disposed therein and the composite material having an upper side and a lower side defining a material thickness, wherein the bolt element (100, 100′) has a central longitudinal axis extending in directions defining above and below the bolt element, a head part (104) having a contact surface (102, 102′) defined below the head part in the direction of the central longitudinal axis and a shaft part (106) extending away from the head part (104) in the direction of the central longitudinal axis, the shaft (106) part having a tip (110) provided at a lower terminal end remote from the head part (104) for piercing the component (130), the tip (110) merging into a thread cylinder (114), the method comprising:

• a first step of heating the component (130) in a region of the piercing to be pierced by the tip (110) of the bolt element (100, 100′) to a temperature dependent on the plastic matrix material at which the matrix material of the composite material does not melt but softens or becomes pasty,
• a second step of generating a hole in the component (130) by pressing the tip (110) of the bolt element (100, 100′) against the component (130) in a movement which extends exclusively in the direction of the central longitudinal axis of the bolt element so that the tip (110) is pressed through the component (130) until the upper side of the component confronting the head part (104) of the bolt element (100, 100′) enters into contact with the contact surface and the tip (110) thereby generates a hole in the component (130), and
• a third step of pressing the material of the component located directly around the thread cylinder (114) of the bolt element inwardly into the thread of the thread cylinder (114) by at least one of the following steps:
• expanding the matrix material through the movement of the bolt element through the composite material and pressing the matrix material inwardly by the outwardly disposed material, and
• by the pressing action of a die button,
• thereby forming an internal thread in the wall of the hole which engages the thread of the thread cylinder (114).