Location

Williamsburg, VA

Start Date

1-1-1988 12:00 AM

Description

The mechanical strength of composite laminates is sensitive to the presence of porosity. Porosity in laminates is generally considered to be a random distribution of voids incurred during the manufacture process. Larger, interlaminar voids typically result from trapped air or moisture; smaller, intralaminar voids may occur between fibers due to improper wetting or the release of volatile gases during the cure cycle. Porosity has its greatest effects on matrix-dominated mechanical properties such as compressive strength, transverse tensile strength and interlaminar shear strength (ILSS). Judd and Wright [1] have surveyed the existing data and made an appraisal of the effects of voids on the mechanical properties of composites. In a study of porosity in filament wound/CVD carbon-carbon composite [2], the transverse tensile strength was found to decrease exponentially with increasing porosity and followed an empirical equation often attributed to Ryshkewitch [3] and Duckworth [4]: σ = σmaxeBP (1) where σmax is the strength at zero porosity, P is the volume fraction of porosity, and B (a negative number) is an empirical constant that depends on pore size, shape, and orientation. More recently Yoshida et. al.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

7B

Chapter

Chapter 5: Adhesive Bonds and Composites

Section

Composites—Defects

Pages

1075-1082

DOI

10.1007/978-1-4613-0979-6_24

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Mechanical Strength Degradation of Graphite Fiber Reinforced Thermoset Composites Due to Porosity

Williamsburg, VA

The mechanical strength of composite laminates is sensitive to the presence of porosity. Porosity in laminates is generally considered to be a random distribution of voids incurred during the manufacture process. Larger, interlaminar voids typically result from trapped air or moisture; smaller, intralaminar voids may occur between fibers due to improper wetting or the release of volatile gases during the cure cycle. Porosity has its greatest effects on matrix-dominated mechanical properties such as compressive strength, transverse tensile strength and interlaminar shear strength (ILSS). Judd and Wright [1] have surveyed the existing data and made an appraisal of the effects of voids on the mechanical properties of composites. In a study of porosity in filament wound/CVD carbon-carbon composite [2], the transverse tensile strength was found to decrease exponentially with increasing porosity and followed an empirical equation often attributed to Ryshkewitch [3] and Duckworth [4]: σ = σmaxeBP (1) where σmax is the strength at zero porosity, P is the volume fraction of porosity, and B (a negative number) is an empirical constant that depends on pore size, shape, and orientation. More recently Yoshida et. al.