A study of interfacial aspects of epoxy-based composites reinforced with dual basalt and SiC fibres by means of the fragmentation and acoustic emission techniques

Abstract Fibre/matrix interfacial properties and interfacial shear strengths (IFSS) in epoxy composites reinforced by dual basalt and SiC fibres (DFC) were investigated by the fragmentation method combined with acoustic emission (AE) analysis. Statistical analysis of fibre tensile strength was performed in terms of statistical parameters. The tensile strength and elongation of basalt and SiC fibres decreased with increasing gauge length because of the size effect. Fibre tensile strengths above an optimum concentration decreased because of the stress concentrations at lumps in the coating. When an amino–silane coupling agent was used, the IFSS showed significant improvements of more than three times under dry conditions. The IFSS was also considerably improved under wet conditions. This environmental effect is probably due to chemical and hydrogen bonds as well as to interdiffusion effects in two different interphases in the fibre/silane-coupling-agent/epoxy-matrix system. In situ monitoring of AE during the straining of DFC specimens showed the sequential occurrence of two distinct groups of AE data. The first group may have come from fibre breakages, and the second mainly from cracking of the epoxy matrix. Characteristic frequencies coming from the different failure modes of the fibres and epoxy matrix were investigated by fast Fourier transform (FFT) analysis. By setting an appropriate threshold level, a one-to-one correspondence between the number of AE events and fibre breakages was established. This AE method could be correlated well with the fragmentation technique of obtaining the IFSS value. It can be also be applied to semi- or non-transparent composites where visual observation is not possible.

[1]  Joung-Man Park,et al.  Improved interfacial shear strength and durability of single carbon fiber reinforced isotactic polypropylene composites using water-dispersible graft copolymer as a coupling agent , 1996 .

[2]  H. Wu,et al.  Weibull analysis of strength-length relationships in single Nicalon SiC fibres , 1992 .

[3]  L. Schadler,et al.  Acoustic emission in single filament carbon/polycarbonate and Kevlar®/olycarbonate composites under tensile deformation , 1990 .

[4]  Hideharu Fukunaga,et al.  The evaluation of the strength distribution of silicon carbide and alumina fibres by a multi-modal Weibull distribution , 1986 .

[5]  M. Piggott,et al.  Interfacial effects in carbon-epoxies , 1985 .

[6]  T. Ishikawa.  Recent developments of the SiC fiber Nicalon and its composites, including properties of the SiC fiber Hi-Nicalon for ultra-high temperature , 1994 .

[7]  J. M. Park,et al.  Interfacial shear strength and durability improvement by monomeric and polymeric silanes in basalt fiber/epoxy single-filament composite specimens , 1991 .

[8]  V. Manoranjan,et al.  Prediction of fibre strength at the critical length: a simulation theory and experimental verification for bimodally distributed carbon fibre strengths , 1993 .

[9]  A. R. Baker,et al.  An enhanced, acoustic emission-based, single-fiber-composite test , 1992 .

[10]  L. Drzal,et al.  Adhesion of graphite fibres to epoxy matrices. II. The effect of the fibre finish , 1983 .

[11]  A. Pollock.  Acoustic emission - 2: Acoustic emission amplitudes , 1973 .

[12]  J. M. Park,et al.  Interfacial shear strength and durability improvement by silanes in single-filament composite specimens of basalt fiber in brittle phenolic and isocyanate resins , 1994 .

[13]  D. Adams,et al.  Development and evaluation of surface teratmetns to enhance the fiber-matrix adhesion in PAN-based carbon fiber/liquid crystal polymer composites. Part II: Electrochemical teatments , 1993 .

[14]  S. Zhandarov,et al.  Interfacial adhesion and failure modes in single filament thermoplastic composites , 1994 .

[15]  S. Phoenix,et al.  Interfacial shear strength studies using the single‐filament‐composite test. Part II: A probability model and Monte Carlo simulation , 1989 .

[16]  irwin Guttman,et al.  Introductory Engineering Statistics , 1965 .

[17]  L. Drzal,et al.  Adhesion of Graphite Fibers to Epoxy Matrices: II. The Effect of Fiber Finish , 1983 .

[18]  A. Kelly,et al.  Tensile properties of fibre-reinforced metals: Copper/tungsten and copper/molybdenum , 1965 .

[19]  S. Patankar.  Weibull distribution as applied to ceramic fibres , 1991 .

[20]  D. Stone,et al.  Continuous micro-indenter push-through technique for measuring interfacial shear strength of fiber composites , 1989 .

[21]  J. P. Bell,et al.  Interfacial shear strength and failure modes of interphase-modified graphite-epoxy composites , 1989 .

[22]  S. Phoenix,et al.  Interfacial Shear Strength Studies Using the Single-Filament-Composite Test. I: Experiments on Graphite Fibers in Epoxy , 1989 .