Design, development, and implementation of test methods for determination of through thickness properties of laminated composites

Test methods for the measurement of through thickness elastic and strength characteristics of laminated composites in tension, compression, and shear have been investigated. Each method studied involved finite element analysi s and practical testing on unidirectional carbon-epoxy laminated specimens. Tensile and compressive methods involved the direct loading of a parallel sided block for determination of elastic constants and a waisted specimen w ith square cross-section for the measurement of elastic constants and stren gth. Experimental results validated the numerical studies. The shear method consisted of a specimen bonded between steel plates, which were loaded in compression, inducing shear stresses in the specimen. Two specimen designs were developed. The first, for measurement of shear moduli only, was a para llel sided block. Specimen length and thickness were optimised for two fibr e directions. The second design, for measurement of shear strengths, was a waisted specimen sandwiched between two epoxy blocks and subjected to a com bination of sheer and transverse compressive loading. Tests confirmed the v alidity of the shear moduli measurements. However, it was found that a purl shear failure mode was not achievable. Failure always occurred by a combin ation of sheer and transverse tension.