Vac­u­um infu­sion for large-area fiber com­pos­ite com­po­nents — an alter­na­tive to injec­tion molding

Com­po­nents made of fiber com­pos­ites are often sig­nif­i­cant­ly lighter than injec­tion-mold­ed plas­tic com­po­nents for the same per­for­mance, because the fibers give the mate­r­i­al extreme strength in the lon­gi­tu­di­nal direc­tion and thus indi­rect­ly reduce com­po­nent weight, since less mass is required for the same load-bear­ing capac­i­ty. This prop­er­ty makes fiber com­pos­ites attrac­tive for all areas of appli­ca­tion in which weight reduc­tion plays a role, e.g. motor sports, boat build­ing or aerospace.

A spe­cial fea­ture of fiber com­pos­ites is that their stiff­ness and ten­sile strength depend on the ori­en­ta­tion of the fibers with­in the com­pos­ite matrix. This allows their mechan­i­cal prop­er­ties to be flex­i­bly tai­lored to the area of appli­ca­tion. This pays off both in terms of price and weight, as the com­po­nents can be opti­mized specif­i­cal­ly along the stress curves in use.

For exam­ple, fiber-rein­forced com­pos­ites make it pos­si­ble to devel­op lighter ten­sion rods that are enor­mous­ly sta­ble against loads in the direc­tion of ten­sion, but less able to with­stand orthog­o­nal forces (which occur less frequently).

The dis­ad­van­tage of fiber-rein­forced plas­tics becomes appar­ent toward the end of their ser­vice life. Unlike injec­tion-mold­ed parts, fiber-rein­forced parts are not read­i­ly recy­clable. The rea­son for this is the chem­i­cal com­po­si­tion of the mate­r­i­al. It is not a homo­ge­neous mass, but a com­pound of poly­mers (often duromers) and rein­forc­ing fibers that stick togeth­er. This bond is almost impos­si­ble to reverse in terms of process tech­nol­o­gy. Com­po­nents man­u­fac­tured in this way can there­fore not sim­ply be melt­ed down and recycled.

On the one hand, this is detri­men­tal to the com­pa­ny’s envi­ron­men­tal bal­ance sheet, since fiber com­pos­ites are not biodegrad­able and require cost­ly dis­pos­al. On the oth­er hand, it is detri­men­tal to prof­itabil­i­ty, as the com­pa­ny has to arrange and finance dis­pos­al — a chal­lenge that is cur­rent­ly occu­py­ing the oper­a­tors of off­shore wind farms, for exam­ple. For this rea­son, fiber com­pos­ites are crit­i­cal for appli­ca­tion areas with a short ser­vice life.