The Interfacial and Compressive Properties of Polybenzothiazole Fibers
Abstract
This report evaluates the interfacial and compressive properties of polyparaphenylenebezobisthiazole (PBT) fibers in an epoxy matrix (Epon 828, Shell Chemical Co., cured with metaphenylenediamine). The interfacial shear stress was measured by the single fiber tensile coupon meathod, while wettability of the fiber was determined from the contact angle. A technique was developed for measuring compressive strength of single fibers by placing a matrix-embedded fiber in axial compression, and observing microscopically the onset of kinking or fracture in the fiber. The difficulty in developing adhesion between PBT fibers and epoxy matrices appears to be due to three factors: 1) the surface of the PBT fiber is thermally stable and very non-reactive making traditional methods of improving fiber-matrix adhesion inoperative; 2) the Poisson's ratio of the PBT fiber is greater than that of the typical structural matrices used in advanced composites, which results in a net tensile interfacial force causing separation of the fiber and matrix under tensile loading conditions; 3) the fibrillar nature of the fiber causes interfibrillar failure under shear loading which is the upper limit axial shear strength. The interfacial shear strength attainable with the PBT fibers and epoxy is only of the order of 1.5 ksi versus the value of 3.6 ksi obtained with Kevlar-49 in the same matrix. The compressive strength of PBT fibers is substantially below that of the tensile strength of the same fibers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1986
- Accession Number
- ADA171620
Entities
People
- L. T. Drzal
Organizations
- Wright Laboratory