Composite Technology Laboratory Rene Herrmann 2011

vacuum lamination lamination by hand results in fiber volume fraction f<30%. This corresponds to small youngs modulus and large resin consumption vaccum lamination can be done either wet or with infusion. Both metods have advantages and drawbacks

wet vacuum lamination 1 After mould preparation the fibers are wetted by hand and the vacuum bag is placed later over the laminate. This process is often called vacuum bagging. Disadvantage is that you work against geltime and fiber alligement my not be perfect, when wetting the fibers you have to be very careful to insure that the vacuum sealant is not getting wett, otherwise you nerver get the vacuum bag tight. Advantage is that the wetting of the fibers is garantied, because you put the resin by yourself everywhere you want it.

vacuum infusion The process is sometimes also called injection because it is possible to feed the resin either by aid of vacuum or by a resin pump and vacuum. Resin pumps mix the resin themselfs and costs in access of 10keuros. However they can feed resin very fast, meaningful especially for large laminates. The advantage of infusion is that the fibers can be placed without time limitation, their alligment can be made to perfection. The vacuum qualtity of the bag can be tested before the resin is let in. Vacuum leaks can be repaired. The disadvantage is fiber wetting, especially in thick laminates exists the risk tat not all fibers have received resin (shallow surface wetting)

Economy of lamination The following explores the costs of manufacturing as compared to the youngs modulus achieved. The calculation is based on that laminates have not the same thickness but the same tensile strength. This means that a smaller youngs modulus has to be compansated by greater thickness, that is:

economy of hand laminate You need fibers and resin, some brushes (1euro). Fiber volume fraction f=30% gives for E type glasfiber a youngs modulus of about 23 GPa. For vacuum laminate you need fibers, resin AND vacuum packaging material, with same fibers you will get an approximate youngs modulus of 36GPa. The relative difference between these cases results in that the hand laminate with same strength 36/23=1,56 times the thickness. This difference is resin volume costs and increased mass. However the hand laminate saved the costs for vacuum packaging material and pump.

Economy of vacuum lamination It is wrong to assume that vacuum lamination will always use less resin than hand lamination, some resin goes to the vacuum packaging material and inlet. This resin is relatively much in thin and small laminates. The vacuum laminate needs peel ply (1euro/m^2), release foil (0,85euro/m^2) and flow mat (1,5euro/m^2). The vacuum foil/bag is around 1 euro/m^2). The vacuum sealant is around 0,2 euro/m. You need inlet and outlet (2 euro) with possible valves and a vacuum pump (2000 euro).

References - processes google infusion (yacht) google vacuum bagging kite board google handlamination boat google spray gun / chopped strands

Home work – dont turn in but be ready to do in exam the same Calculate a case study for a small lamination work shop. Assume the product are car parts (motor hood), essentially a panel. Assume 1720g/m^2 glasfiber, 1000 pieces per year. Vacuum pump has 5 years life span. Assume the motor hood is about 1,6m x 1,8m. Assume that the flow mat absorbs 500ml resin. What are the prices in each case?