Bonding objects together

A method of bonding a first object to a second object, the method comprising:

• providing the first object, wherein the first object extends between a proximal end and a distal end and comprises a first object body and at least one protrusion distally of the first object body, wherein the protrusion forms the distal end and comprises thermoplastic material in a solid state,
• providing the second object comprising a proximal surface,
• applying a mechanical pressing force and a mechanical excitation capable to liquefy the thermoplastic material to at least one of the first and second objects until a flow portion of the thermoplastic material is flowable,
• stopping the mechanical excitation and letting the thermoplastic material resolidify to yield a connection between the first and the second object,
• wherein the second object provided comprises a region of low density,
• wherein the protrusion penetrates the region of low density at least partly before the thermoplastic material is made flowable,
• wherein the first object comprises a protruding portion after the step of letting the thermoplastic material resolidify,
• wherein the protruding portion penetrates the region of low density at least partly,
• wherein the method comprises a step of changing a compressive strength of the region of low density at least locally such that a critical compressive strength needed for the liquefaction of the thermoplastic material is generated,
• wherein changing in the compressive strength is increasing the compressive strength from a compressive strength that is below a critical compressive strength needed for liquefaction of the thermoplastic material to a compressive strength that is above the critical compressive strength needed for liquefaction of the thermoplastic material, and
• wherein the second object comprises synthetic fibers or a thermosetting polymer.