s.m tahami - Composite Department, Malek Ashtar University of Technology, Tehran, Iran.
m farhadinia - Composite Department, Malek Ashtar University of Technology, Tehran, Iran.
y aljasem - Composite Department, Malek Ashtar University of Technology, Tehran, Iran.
j Eskandari Jam - Composite Department, Malek Ashtar University of Technology, Tehran, Iran.

The low interlaminar strength of composite laminates is one of major disadvantages which delayed the widespread use of composite laminates in structures. For this reason, manyefforts have been made to improve the interlaminar strength. Stitching through the thickness of a laminate is indeed valid inthe improvement of interlaminar fracture toughness[1]. Good fracture toughness improvement is reported. On the other hand, the behavior of the matrix is generally believed to play akey role in determining the delamination resistance [2]. Epoxies in the cured state are brittle and have fracture energiestwice of magnitude lower than modern thermoplastics and other high performance materials [3]. In the present study, it isattempted to investigate the interlaminar fracture toughness of Glass/Epoxy composite laminates by using four types of material at their midplane of 12 plies Glass/Epoxyunidirectional laminated Composites during the lay-up process