RTM Resin Infusion

RTM Light or Resin Transfer Moulding

RTM Light is a closed mould method of production where a dry glass or other reinforcement matrix is placed in a mould and consolidated with polyester or other resin without spraying, handling of wet resin or manual consolidation. 


In brief the glass fibre reinforcement (including a flow media) is placed into the mould and shaped to fit. A structured inner liner is then placed into the mould to locate the reinforcement and any inclusions such as fixing plates etc. The cavity created by the glass is evacuated by vacuum and then the resin is infused and drawn into the reinforcement matrix by the vacuum through injection ports. Mould flow of resin is controlled so that wet-out of the reinforcement is 100% with no voiding or air entrapment in the laminate. In the process a very precise resin to glass ratio is achieved yielding optimum mechanical properties, predictable and uniform laminate thickness and excellent surface finish to the inner faces.

 Similar to flexible bag moulding but employing a hard inner liner which is usually made of translucent polyester or vinyl-ester resin. Additional advantages include ability to produce 2 high gloss faces, interior surface is of superior finish and if required, can be gel-coated. The process produces products of uniform, predictable physical properties, qualities and very precise laminate thickness.


As stated above the laminate resulting from infusion tightly controls the resin:glass ratio providing parts of optimum strength and strength or inserts in specific areas. From an engineering perspective the resin matrix is primarily used to hold the glass reinforcement in place. While the resin is relatively flexible the glass is rigid with high tensile properties. The more accurate the use of resin and the better located and tightly packed the glass matrix, the more mechanically efficient the reinforcement.


Depending on the complexity of the part more than one item per mould per shift can be obtained. Excellent quality finishes can be achieved to both the exterior visible surface and the interior face therefore two sided parts are possible by applying the gelcoat to the inner liner in RTM.

Inclusion of other components such as timber etc can be done during the single cycle. Often the addition of sections to the back of the laminate can result in telegraphing of the piece due to shrinkage movement during non uniform cure. As all components are infused simultaneously the cure is uniform and this problem can be avoided. This is particularly relevant for automotive quality parts.


For the client, the primary benefits are part uniformity and increased speed of production. Known engineering detail can be specified and achieved in production in most cases saving weight and increasing predictable properties. 

There are additional benefits in knowing that the part is made using an environmentally friendly production technology.