Title: Cement-Based Cross-Ply and Sandwich Laminate Composites

Author(s): A. Pivacek, G. J. Haupt, R. Vodela, and B. Mobasher

Publication: Symposium Paper

Volume: 190

Issue:

Appears on pages(s): 55-76

Keywords: fiber-reinforced concrete; high-performance concrete; pultrusion; filament winding; laminates; com-posites; strength glass fibers; sandwich laminates

DOI: 10.14359/5721

Date: 4/1/2000

Abstract:
A class of new structural materials with a significant degree of ductility and strength are introduced that are durable, strong, and cost effective. High fiber content cementitious materials (FRC materials) are manufactured using a computer controlled closed loop system for pultrusion and filament winding. Composites consisting of unidirectional lamina, and [0/90/0] are manufactured. In addition, sandwich composites with a lightweight aggregate core and 0/90 lamina as the skin elements are studied. Mechanical response of laminates is measured using closed loop uniaxial tensile and flexural tests. Results indicate that tensile strength of composites containing 5% alkali-resistant (AR) glass fibers can exceed 40 MPa. The ultimate strain capacity can also be increased to more than 2% using cross plies at various orientations. Significant cost savings and weight reduction may be achieved by replacing the inner layers of the boards with a lightweight aggregate mixture at a marginal loss of strength. The ultimate strain capacity of the composites is a function of ply orientation, thickness, and stacking sequence. Various mechanisms of delamination, debonding, and crack deflection are identified, resulting in an ultimate strain capacity of 2%, and a fracture toughness as much as two orders of magnitude higher than the conventional FRC materials. The extent of matrix cracking, ply delamination, and crack deflection mechanisms are studied by means of fluorescent microscopy.