Interlaminar Fracture Of Unidirectional Reinforced Composites With Toughnened Resin Systems

Several undisclosed fiberglass and carbon fiber laminates with toughened resin systems were tested and examined. Experiments were conducted to determine Modes I and II interlaminar fracture toughness for each of the nine laminates with varying types of processing forms such as roving, tape, and slit tape of glass and carbon fibers. Fractography was then used to correlate the fracture toughness results with the unique characteristics and failure mechanisms. Overall, fiberglass laminates had larger interlaminar fracture toughness for both Modes I and II over the carbon laminates. This was also confirmed by the significant amount of the fractured surface area and complex fracture features of the fiberglass laminates.
Mode I fiberglass specimens had a large amount of fiber bridging, whereas carbon specimens had relatively very little. Of the fiberglass specimens, fiber bridging occurred more prevalently in the roving material than tape. However, the onset of fracture toughness was very similar for the roving and tape fiberglass resin systems. For the glass and carbon fiber laminates with the same resin systems, an increase in fracture toughness was observed for fiberglass due to a higher strain and a lower modulus and stiffness.