Method of manufacturing a lightweight, structurally reinforced object of thermoplastic material

A method of manufacturing a lightweight, structurally reinforced object of thermoplastic material comprising at least one reinforcement zone, the method comprising the following steps:

• a) providing a heatable rigid forming chamber comprising a chamber volume surrounded by chamber walls and an openable chamber lid;
• b) providing a plurality of thermoplastic lofting bodies and a plurality of thermoplastic reinforcement bodies, the lofting bodies and the reinforcement bodies comprising identical or mutually compatible thermoplastic material, the reinforcement bodies further comprising reinforcement fibers embedded in the thermoplastic material, the lofting bodies being
• i) heat-loftable bodies comprising a thermoplastic matrix containing an elastically compressed assembly of reinforcement fibers embedded therein,
• and/or
• ii) lofty non-woven bodies comprising an elastically compressible assembly of reinforcement fibers and thermoplastic fibers;
• and optionally providing a plurality of rigid filler bodies;
• c) at a base temperature below a thermoplastic softening temperature, loading the chamber with lofting bodies, reinforcement bodies, and optionally with filler bodies, so as to form an arrangement corresponding to the intended object, wherein the lofting bodies have an initial first volume V1, the reinforcement bodies have an initial second volume V2, and the filler bodies have an initial third volume V3, and wherein the sum V0=V1+V2+V3 of said initial first, second and third volumes exceeds the chamber volume V by an excess volume Ve which is in the range from 0.5 to 0.95-times the initial first volume of any lofting bodies which are lofty non-woven bodies (ii);
• d) closing the chamber lid, whereby the lofting bodies assume a loaded first volume V1′, the reinforcement bodies assume a loaded second volume V2′, and the filler bodies assume a loaded third volume V3′ substantially equal to the initial third volume V3, and whereby the sum V0′=V1′+V2′+V3′ of said loaded first, second and third volumes is equal to the chamber volume V, whereby any lofting bodies configured as lofty non-woven bodies are elastically compressed, thereby building up a first amount of internal pressure;
• e) heating up the chamber to a processing temperature above said thermoplastic softening temperature, whereby the reinforcement bodies and the lofting bodies are brought into a thermoplastically formable state, and whereby any lofting bodies configured as heat-loftable bodies are caused to build up a second amount of internal pressure;
• f) after a predetermined processing time, allowing the chamber to cool down, whereby the reinforcement bodies and the lofting bodies solidify, followed by removing any filler bodies, thereby obtaining said structurally reinforced object.