The mechanical properties of the Composites are superior to the sum of the properties of its components.
Bulk Molding Compound
Bulk Molding Compound (BMC) is a bulk pre-preg made by combining chopped glass strands, resin (typically polyester), filler, catalyst and other additives. The final mix and homogenization is made in different types of kneeders / mixers. BMC is compacted and packed in styrene tight bags in variable size, fitting all UP injection moulding machines stuffer units. BMC delivers excellent electrical resistance, good mechanical properties and outstanding heat and corrosion resistance. BMC is suitable for several processes, including Compression and Injection Molding. It is used in automotive, electrical & electronics, aerospace and defense applications.
LFT-G (or LGT-P)
In the LFT-G (or LGT-P) process, the resin is heated together with additives to a molten phase and pumped to the die-head. The continuous roving is pulled through dispersion die, ensuring good impregnation of the glass fibers by molten polymer and consolidation into a rod. After cooling, the rod is chopped into reinforced pellets of 12-25 mm length. The end-users can use injection or compression molding to make final parts with well defined properties.
Filament Winding is a process of winding resin impregnated fiberglass (or carbon fiber and other reinforcements) on a mandrel surface in a precise geometric pattern. This is accomplished by rotating the mandrel while a delivery head positions the wet band onto the mandrel surface. Filament winding process is widely applied in manufacturing pipes, tanks, cylinders and other rotating shapes.
In the Continuous Panel process, the resin mix is uniformly deposited onto the moving film at the constant speed. The thickness of the resin is controlled by the draw-knife. The fiberglass roving is chopped, metered and uniformly distributed onto the resin. After chopping, the top film is laid-on forming a sandwich structure. The wet assembly travels through the curing oven before de-molding.
Pultrusion process is used to make continuous, constant cross-section shapes, either solid or hollow shapes. The process involves pulling continuous rovings, mats or fabrics through an impregnation bath, squeeze-out and shaping section and the heated die. Because it takes hundreds of roving packages to make a Pultruded part, creels must be used to store them and guide them efficiently. By use of beck tension and forming tools, the reinforcements are guided precisely into an exact location in the bath and in the final part. The excess resin is gradually squeezed out before entering the curing die. The final shape is formed under high temperature and high pressure (created by packing resistance and heat expansion) conditions, making it virtually void free. Low voids are critical for Electrical parts. Because of the high reinforcement loading, the resulting parts can have very high mechanical strength and modulus, in the zero degree direction. This makes Pultruded shapes excellent structural members (I-beams, angles and T-sections) used in gratings and large structures. Variations of Pultrusion process included: pull-forming, using UV or Radiation curing and simple coating die production of strength members.
Hand Lay-up is an open molding process. The reinforcement, in form of fiberglass strands, mat, or woven roving, is first laid into a mold which has been coated with a release agent and a gel coat. Then a resin mix is applied by hand, using a brush or spray gun. A roller is then used to ensure uniform impregnation, complete wet-out and removal of any trapped air bubbles.
At the heart of the Spray-Up process is the spray or chopper gun, which simultaneously and uniformly chops the assembled roving, mixes it with the resin, containing initiator, accelerator, filler, pigment and other additives, and directs the mixed stream onto an open mold. The roving is chopped into a specific length. Compaction, wet-out and air-release are accomplished, using a roller as in the Hand Lay-Up process. One good appearance side is possible with this process. The material selection is important. The resin should be easy to atomize. The fiberglass roving should be of moderate stiffness, easy to chop, with good static and ribbon control, ensuring efficient processing.
Glass Mat Reinforced Thermoplastics(GMT)
GMT (Glass Mat Thermoplastic) is a multi-step process. First, a needled mat is used or a mat is formed in-situ by chopping assembled roving. Then, one or two layers of reinforcing mat are sandwiched between two or three sheets of polypropylene. This sandwich is then heated and consolidates into a semi-finished sheet product. The GMT sheets are then heated and molded using stamping or compression process to make complex finished parts.
Resin Transfer Molding (RTM)
Resin Transfer Molding (RTM) is a closed mold process which is used to make complex shapes. In this process, liquid resin is injected into a closed mold cavity which contains pre-placed reinforcement. The resin flows through the reinforcement, such as fiberglass mats, preforms or fabrics, impregnating and wetting it out. The composite material is cured under a low pressure and RT or moderate heat to form the final part.
Extrusion and Injection
There are two steps in extrusion-injection process. Step one is “extrusion”: mixing the thermoplastic resin with glass fiber in an extruder, thus forming reinforced thermoplastic pellets. Step two is “injection”: converting the reinforced thermoplastic pellets into different parts using an injection molding machine. The advantages of the extrusion compounding process lie in its low cost conversion, due to high efficiency screw design, and versatile formulation possibilities.