referring now to the figures of the drawing in detail and first , particularly , to fig1 thereof , there is shown a wall or structural element produced as a composite in the example of a door for a motor vehicle . the door includes two wall or structural elements respectively produced as a composite type of construction and secured to each other , but leaving a channel 5 free between them because of a required fitting of a window pane 6 and a mechanism required for moving it . a thin - section wall part 1 for an outer skin of the motor vehicle door is formed of sheet metal , is adjoined by a molding 4 formed of a foamed synthetic , biological or naturally derived binder 2 and reinforcing elements 3 surrounding the latter and thereby fixed in their position . the molding 4 is bonded to a second molding 4 a , or composite part , forming an interior paneling of the vehicle door . provided between the two moldings 4 , 4 a is the channel 5 for receiving the window pane 6 , a guide rail 7 required for guiding the window pane 6 , and further actuating elements ( not shown in the drawing ) for moving the window pane 6 . the outside of the second molding 4 a is covered by a decorative layer 8 shown as a thin - layered wall part and is solidly bonded to the molding 4 a by foaming on , adhesion or the like . the production of the wall or structural element shown in fig1 takes place by placing the wall part 1 , serving as the outer door skin formed of sheet metal , into a mold and covering its inner side uniformly with a layer of the reinforcing element 3 . renewable raw materials in the form of stalks and stalk sections or fibers and bundles of fibers as well as nonwovens and the like produced from the latter are used as the reinforcing elements 3 . preferably considered here as renewable raw materials are monocotyledons and dicotyledons , which are distinguished by outstanding mechanical properties . in the case of dicotyledons , the periphery of the stalk consists of a bast ring , which is composed of extremely long and high - strength fibers , particularly in the case of bast fiber plants . the cylindrical arrangement of the bast fibers represents what is mechanically an ideal cross section for bringing about a particularly high modulus of elasticity as well as a high flexural strength and buckling resistance . although monocotyledons do not have a pronounced bast ring , they have a ring of shorter - fibered sclerenchyma , adjoined in the case of many species by a high - strength ring of vascular bundles , which are accompanied by high - strength mechanical tissue . in addition to this , they have a highly pronounced epidermis of great toughness . the renewable raw materials used according to the invention are also advantageous to the extent that their fibers are embedded in a parenchyma matrix . the parenchyma is resistant to pressure and has a large lumen and , in interaction with the peripheral strengthening strands , allows considerable flexing . in the case of dicotyledons , on the other hand , in the center of the stalk there is instead of the parenchyma a core of wood , which is likewise characterized by an extremely low wood density . after applying the reinforcing elements 3 of renewable raw materials to the wall part 1 , a counter - mold ( not shown ) is placed on and the binder 2 is introduced via corresponding cannulas or injection nozzles into the hollow mold thus formed . the binder 2 is free - flowing during injection process , with the result that it flows completely around the reinforcing elements 3 and can penetrate into all the intermediate spaces . after a time delay , the binder 2 will foam and secure the reinforcing elements 3 in place . the foaming process commences only after a certain time delay after a corresponding distribution of the binder 2 . the foamed binder 2 adheres solidly to the reinforcing elements 3 and fixing the latter in its position . once the inner side of the wall parts 1 ( door panel ) has been primed , if need be , before being placed into the mold , the molding 4 including the foamed binder 2 and reinforcing elements 3 also undergoes a solidly adhering , full - area bond with the wall part 1 . the result being a one - piece composite is obtained after removing the counter - mold . in the case of the exemplary embodiment represented on the basis of a vehicle door , the second molding 4 a can be separately produced in the same way as a thin - section wall part 1 onto an interior paneling or the decorative layer 8 . the two composite parts subsequently being solidly bonded to each other in a sandwich - like manner with recesses forming intermediate spaces for receiving the window pane 6 and necessary guiding and actuating elements . with composites produced in this way , which may be configured equally as a member or a wall element of the body or as a bumper etc ., outstanding side impact protection in the motor vehicle is achieved by increasing the moment of resistance and the deformation path . since impact forces are uniformly distributed and dissipated and introduced into the cage structure of the passenger compartment , the impact energy is substantially absorbed . at the same time , the heat insulation of the body is improved and consequently the co 2 emission and the energy consumption are reduced . finally , the climatic conditions in the interior of the vehicle are also improved . on account of the composite type of construction including a sheet - like wall part 1 and the reinforced molding 4 ( foam element ), the body panel can be made much thinner than is generally customary , with the result that the expenditure on material for the body panel , which is a high consumer of primary energy , and ultimately the weight of the body can usually be lowered . in addition , in the event of impact , no sharp edges are produced , since the composite material does not splinter , and consequently the safety of the vehicle occupants and other persons involved in an accident is increased . according to the invention , it is also possible , however , contrary to the production process described above , to produce the reinforced molding 4 , 4 a separately in a mold , i . e . separately from the wall part 1 ( or 8 ), and subsequently adhesively bond it to the thin - section wall part 1 . even greater rigidity of the structural element produced as a composite part can be achieved by using integral foam , it being possible in this case to reduce further the wall thickness of the thin - section wall part 1 . [ 0064 ] fig2 shows a second variant of the invention also shown by example as the door of a motor vehicle in which the impact protection is further improved and the thickness of the wall part 1 is even further reduced . the wall part or component differs from that represented in fig1 essentially in that the thin - section wall part 1 , i . e . the outer skin of the door , the body , a member etc ., is backed by a hard shell or insulating layer 9 formed by compression molding or injection molding 9 , preferably using reinforcing elements 3 of renewable raw materials in the hard shell 9 . in the way described above , the molding 4 including the reinforced foam or integral foam and reinforcing elements 3 are applied to the hard shell 9 , in a solid bond with the shell 9 , and a further hard shell 9 is applied to the molding 4 as a counter - chord . it can also be seen from fig2 that , to save primary material , inside the molding 4 there is a recycled core or insulating core 10 formed of a lightweight recycled material . the size of this recycled core 10 is variable . it may ultimately reach over the entire cross section of the molding 4 and , moreover , be reinforced with renewable raw materials or other materials . it goes without saying that this molding can also be produced separately , as described with reference to fig1 and then be adhesively bonded to the thin - section wall part 1 , in order to form the composite in this way . in order to form the channel 5 , the second molding 4 a , or the second structural element , is solidly joined onto the structural element thus formed . in fig3 there is reproduced a third variant of a wall or structural element , configured as a composite , for the motor vehicle door . in this case , the wall or structural element is reinforced by transverse cross - pieces 11 a , which are part of half - shells 11 produced separately and solidly bonded to the wall part 1 . the half - shells 11 are placed with positive engagement into the wall part 1 and held against the latter and with respect to one another by adhesion or foaming in . the half - shells 11 with the transverse cross - pieces 11 a extending substantially perpendicularly away from the latter , are produced with the preferred use of renewable raw materials as reinforcing elements 3 . the cavities formed by the half - shells 11 and transverse cross - pieces 11 a are filled by reinforcing elements 3 composed of renewable raw materials and foam having a binder 2 , or else are provided with a recycled core or completely with a foam filling . the half - shells 11 filled in this way are covered with a hard shell 9 . the hard shell 9 forms a solid bond with the half - shells 11 or the transverse cross - pieces 11 a , for example by the foam - filling of the cavities . the hard shells 9 and the half - shells 11 are produced by a compression - molding technique or else an injection - molding or blow - molding technique , with or without the use of reinforcing elements 3 . with the third variant , particularly high rigidity and flexural strength can be achieved resulting in a further reduction in the material thickness of the outer skin ( wall part 1 ). as already described above , the composite element embodiments may be in the form of a vehicle door . there may be connected to the composite element thus produced , the second molding 4 a , into which various functional elements ( not shown ), such as map pockets , armrests or the like , may be integrated . in this case , the thin - section inner wall part ( decorative layer 8 ) may also be configured as a thin sheet - metal skin , in 20 order to bring about a further increase in the rigidity of the vehicle door . it can be seen from the representations of a passenger vehicle door , or the part of the body receiving the latter , reproduced in fig4 a and 4 b , how the door in the form of a rigid shell covers over the fold of the door opening over its full area — with the exception of the window region — and consequently the energy generated during impact ( large arrow ) is dissipated over a large area onto the entire door fold in the direction of the small arrows . in addition , in combination with the dissipation of the forces , the impact energy is absorbed by the compression of the foam core extending over the entire door surface area .