The objective of this study is to improve the fracture toughness of continuousfilament graphite-epoxy composites. The method used is intermittent interlaminar bonding, which can lead to a large increase in the fracture surface area. In this study I achieved intermittent bonding through introduction of thin perforated Mylar film between the layers of the composite.
The crack growth resistance curves (R-curves) for the treated and the untreated specimens have been drawn to study the total fracture behavior of these specimens. In this study, the stress intensity factor at fracture was increased from about 140kg/$mm^{\frac{3}{2}}$ for TYPE-Ⅰ specimens to about 380 kg/$mm^{\frac{3}{2}}$ for TYPE-Ⅱ specimens and 390kg/$mm^{\frac{3}{2}}$ for TYPE-Ⅲ specimens, while tensile strength dropped from 610 MPa for TYPE-Ⅰ specimens to 595 MPa for TYPE-Ⅱ specimens and 575 MPa for TYPE-Ⅲ specimens, and elastic modulus remained the same at about 70 GPa. An approximate analysis is presented to explain the observed improvement in fracture toughness.
