Location

Snowmass Village, CO

Start Date

1-1-1995 12:00 AM

Description

Advanced composites are not without trade-offs. Their increased designability brings an increase in the complexity of their internal geometry and, as a result, an increase in the number of failure modes associated with a defect. When two or more isotropic materials are combined in a composite, the isotropic material failure modes may also combine. In a laminate, matrix delamination, cracking and crazing, and voids and porosity, will often combine with fiber breakage, shattering, waviness, and separation to bring about ultimate structural failure. This combining of failure modes can result in defect boundaries of different sizes, corresponding to the failure of each structural component. For example, impacting a graphite/epoxy (gr/ep) laminate locally alters both fibers and matrix, causing cracking, delaminations, fiber displacement and shattering. While normal mode ultrasonics are affected by all these alterations, this technology is more matrix-sensitive than fiber-sensitive. On the other hand, the conductive fibers allow eddy current imaging to isolate any fiber effects. Thus, the two techniques are complementary and yield a more complete picture of the composite damage. Therefore, gr/ep maintainability criteria should require the coordinated use of both EC and UT technologies (with a possible third technology to isolate matrix cracking). Consequently, more than one NDE technique is needed to completely investigate composite structural integrity.

Volume

14B

Chapter

Chapter 5: Engineered Materials

Section

Composite Properties

Pages

1296-1301

DOI

10.1007/978-1-4615-1987-4_165

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Combined Investigation of Eddy Current and Ultrasonic Techniques for Composite Materials NDE

Snowmass Village, CO

Advanced composites are not without trade-offs. Their increased designability brings an increase in the complexity of their internal geometry and, as a result, an increase in the number of failure modes associated with a defect. When two or more isotropic materials are combined in a composite, the isotropic material failure modes may also combine. In a laminate, matrix delamination, cracking and crazing, and voids and porosity, will often combine with fiber breakage, shattering, waviness, and separation to bring about ultimate structural failure. This combining of failure modes can result in defect boundaries of different sizes, corresponding to the failure of each structural component. For example, impacting a graphite/epoxy (gr/ep) laminate locally alters both fibers and matrix, causing cracking, delaminations, fiber displacement and shattering. While normal mode ultrasonics are affected by all these alterations, this technology is more matrix-sensitive than fiber-sensitive. On the other hand, the conductive fibers allow eddy current imaging to isolate any fiber effects. Thus, the two techniques are complementary and yield a more complete picture of the composite damage. Therefore, gr/ep maintainability criteria should require the coordinated use of both EC and UT technologies (with a possible third technology to isolate matrix cracking). Consequently, more than one NDE technique is needed to completely investigate composite structural integrity.