An acoustic emission study of the temperature-dependent fracture behavior of polypropylene composites reinforced by continuous and discontinuous fiber mats

The temperature-dependent fracture toughness, K-Q, and acoustic emission, AE, behavior of glass-mat-reinforced thermoplastic polypropylene (GMT-PP) composites with continuous (GM-C) and discontinuous (GM-D) fiber mats were studied at three different temperatures: -40 degrees C, room temperature (RT) and + 90 degrees C. Apart from the mat type, the matrix viscosity and the fiber/matrix adhesion were also varied in the GMT-PP samples. K-Q was determined on statically loaded single-edge notched tensile (SEN-T) specimens. During loading of the SEN-T specimens, the burst-type AE signals were monitored. It was established that the mat type and the testing temperature strongly affect the fracture-toughness response. The KQ values of the GMT-PPs with GM-C reinforcements were superior to those with GM-D. Matrix and interfacial variables marginally affected the K-Q values, however. Making use of mathematical statistics, correlations were found between K-Q data and selected AE signal parameters. (C) 2000 Elsevier Science Ltd. All rights reserved.