Accession Number : ADA301677

Title :   Effects of Moisture, Residual Thermal Curing Stresses and Mechanical Load on the Damage Development in Quasi-Isotropic Laminates.

Descriptive Note : Interim rept. no. 16,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF ENGINEERING SCIEN CE AND MECHANICS

Personal Author(s) : Kriz, R. D. ; Stinchcomb, W. W. ; Tenney, D. R.

PDF Url : ADA301677

Report Date : FEB 1980

Pagination or Media Count : 135

Abstract : This investigation demonstrates how the maximum moisture absorbed (that is the wet condition) in O/+ or - 45/9O sub s and 0/90/+ OR -45 sub s laminates fabricated from T3OO/52O8 significantly alters the dry stress state and subsequent damage development along the laminate free edge. Emphasis is placed on using reasonable approximations for wet, dry, and out-of-plane elastic properties since these properties are required to predict the damage free stress state at the laminate edge. Classical laminate theory and a finite element model were used to predict stress states prior to the first formation of damage. Crack patterns characteristic of the laminate in a wet or dry condition were also predicted using a shear lag model. Development of edge damage was recorded and observed during the test by transferring an image of the damage from the edge surface on to a thin acetate sheet (replica technique), such that the damage imprinted on the ecetate sheet could be immediately viewed on a microfiche card reader. Moisture was shown to significantly alter the interior and edge dry stress states due to swelling and a reduction of elastic properties. Moisture also reduces the transverse strength in the 90 deg plies such that the first formation of damage in a wet 0/+ OR -45/90 sub s laminate is a simultaneous occurrence of delaminations and transverse cracks in the 90 deg plies. A model was developed in order to predict changes in first ply failure laminate loads due to differences in stacking sequence together with a wet or dry environmental condition.

Descriptors :   *LAMINATES, *HEAT TREATMENT, *CURING, SHEAR PROPERTIES, STRESS ANALYSIS, COMPOSITE MATERIALS, FINITE ELEMENT ANALYSIS, LOADS(FORCES), STIFFNESS, CRACKS, DAMAGE ASSESSMENT, ELASTIC PROPERTIES, MOISTURE CONTENT, RESIDUAL STRESS, FATIGUE(MECHANICS), FAILURE(MECHANICS), THERMAL STRESSES, DELAMINATION, STATIC TESTS, FATIGUE TESTS(MECHANICS), ACETATES.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE