Seminar Series - 1999-2000

Experimental Analysis of Delamination in Laminated Composites With Nanoreinforced Interfaces

Sergiy Sergiyenko
Advisor:  Y. Dzenis

Date:  Tuesday, May 2, 2000
Time:  1:45 p.m.
Place:  W129 WSEC


High specific modulus and strength, good fatigue durability, and excellent corrosion resistance of advanced laminated composites fabricated from thermoset polymer matrices and advanced reinforcing fibers make them attractive for aerospace, defense, and other high-technology applications. However, delamination is an intrinsic failure phenomenon in these materials that often serves as a life-limiting factor. Substantial effort was devoted over the years to find ways to minimize initiation and growth of delaminations in composites. Although some of the methods provide improvement, most of the existing methods are expensive, technologically complicated, and lead to significant increase in laminate thickness and weight. Recently, a new concept of reinforcement of the interfacial area with micro- and nanofibers that are thinner than the main reinforcing fibers was formulated by Dzenis and Reneker (patent pending). An experimental proof of this concept was the objective of this study. The thesis consolidates information and experimental data obtained in the course of investigation of delamination fracture resistance of composites with nanoreinforced interfaces. Experiments were performed on graphite/epoxy composites manufactured from Hexcell T2G190/F263 prepreg. Polymer electrospun nanofibers and metal micro-fibers were used for interface reinforcement. Morphological characterization of the nanoreinforcement was performed by SEM. The nature of resin/nanofiber interaction was studied by DMA. Interlaminar fracture toughness under pure and mixed mode loadings was evaluated by the Arcan test method. Optical and SEM fractographical analysis was performed to reveal the micromechanisms of fracture. Free edge delamination due to interlaminar edge stresses was studied using specially designed laminate specimens. Acoustic emission analysis was used to determine the delamination onset. Ultrasonic scanning was applied for visualization of delaminated areas. The results showed that nanoreinforcement can result in improvement of both interlaminar fracture toughness and strength of advanced composite laminates with the minimum increase of weight.


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