FAILURE MODES IN UNIDIRECTIONAL COMPOSITES UNDER TRANSVERSE LOADING

G. P. TANDON
AdTech Systems Research Inc.

R. Y. KIM
Univ. of Dayton Research Institute

R. E. DUTTON
NIST, Wright Laboratory

ABSTRACT

This paper reports on our attempts to demonstrate potential failure modes under combined thermal and transverse loading of unidirectional composites and to validate the predictions of an analytical model through careful design and testing of composite specimens. Several fiber/matrix combinations are being considered with appropriate variations of the fiber-matrix interfacial bond strength and processing conditions. The interfacial bond strength is reduced in one set of specimens by applying a release agent to the surface of the fiber prior to its incorporation in the matrix. Curing is done both at room and at elevated temperature to account for thermal residual stresses induced from the mismatch in the coefficients of thermal expansion of the constituents. The experimental technique including specimen preparation, test procedures and detection of the sequence of failure events is described. The correlation between the experimental and analytical results is fairly reasonable.