Disadvantages Of Prepreg

The term "prepreg" is actually an abbreviation for the phrase pre-impregnated. A prepreg is a fiber reinforced and pre-impregnated with a resin, most commonly consists of a fabric (Carbon, Kevlar, Glass, etc.) impregnated with a resin maintained in a pre-gelled condition. The primary resin matrix used is epoxy. However, other thermoset resins are made into prepregs including BMI and phenolic resins.

Carbon fiber is first developed in 1958 in Cleveland, OH, by heating rayon strands which was of relatively poor quality and strength. Then, a few years later, the Japanese developed a chemical process for manufacturing the carbon fibers which is still in use today. In 1963, at Rolls Royce in England, industrial scale production and high quality

In this research work the hexply 913/ G801 carbon prepegs, which are widely used in aircraft industries is considered and is a type of biphenol A mixed with the four functional epoxy like TGMDA( tetraglycidyl methylene dianilime), which is often used to manufacture high performance epoxy matrix composite parts because of its relatively higher cross linking density over DGEBA. Epoxy resins based on DGEBA (diglycidyl ether of biphenol A), needs active hydrogen (H) or other active groups to open two epoxy rings, Generally the 913 epoxy resin has a bi component blend of DGEBA and TGMDA with a curing agent/ hardener DDS (Diamino diphenyl sulfone), because the TGMDA is intrinsically brittle and it was expected that the blend of these two systems could provide higher strength, modulus, fracture toughness and high temperature resistance. In this research work a methodological procedure was developed to analyze the cure kinetic parameters and the cure behavior of hexply 913/ G810 carbon epoxy prepeg material. The data can be used to optimize the cure cycles and to minimize the cure cycle time and the process cost. The Fig. 1 shows the chemical structure of the TGMDA and the DGEBA epoxy

Amines are the most commonly used curing agents/hardeners for epoxides. One epoxy ring reacts with each aminoproton. Aliphatic amines are used for low-temperature curing systems(adhesives, coatings, etc.), and aromatic diamines for composite materials. Cyanoguanidine, or dicyanodiamide (Dicy), is a very versatile hardener widely used in one-pack epoxy formulations for prepregs, laminates, powder coatings, etc. Its latency as a curing agent lies in its high melting point (Tm) and in its low solubility in epoxy monomers. The reactions of Dicy with epoxy groups are very complex, complicated by the fact that ‘‘an accelerator’’ such as a tertiary amine is often used (this accelerator works like an initiator for anionic chain polymerization and the reaction is a mixture of polyaddition and chain polymerization). Most of the matrices for aerospace composites are based on a combination of TGMDA and DDS and/or Dicy. The chemical structure of the curing agent DDS (diamino diphenylsulfone) is as shown in the