Transverse Compressive Stress-Strain Behavior of Thick Kevlar/Epoxy Laminates

摘要

The room-temperature compressive stress-strain response of quasi-isotropic Kevlar 49 fabric/epoxy composites was studied. Cylindrical specimens with porosity up to 20% were loaded normal to the plane of fiber reinforcement. Sample porosity was an important factor affecting the shape of the compressive stress-strain curve, modulus, strength, strain to failure, and Poisson's ratio. As a porous specimen was loaded in compression the tangent modulus first decreased due to void collapse, and then increased as complete consolidation was approached. Increasing the porosity from 1 to 20% caused: (a) the initial modulus to decrease from 6.0 to 1.4 GN/m exp 2 ; (b) the strength to reduce from 1150 to 580 MN/m exp 2 ; (c) Poisson's ratio to change from 0.15 to 0.06; and (d) the failure strain to increase from 16 to 26%. Most of the axially compressed cylindrical specimens failed along inclined planes by shearing through many layers of fabric. Broken fibers were observed on the fracture surfaces.