Applied Composite Materials

, Volume 2, Issue 5, pp 313–326 | Cite as

On the failure mode in dry and hygrothermally aged short fiber-reinforced injection-molded polyarylamide composites by acoustic emission



The failure mode in injection-molded short glass (GF) and carbon fiber (CF) reinforced polyarylamide (PAR) composites was studied on compact tension (CT) specimens in as-received (AR), hygrothermally aged (HA) and re-dried (RD) states, respectively, using acoustic emission (AE) and fractography. A significant difference was revealed in the failure manner characterized by the cumulative run, amplitude and energy distribution of the AE events as a function of the water content of the composites. Furthermore, a correlation was found between the cumulative AE events up to the maximum load and the fracture toughness of the composites. It was shown that the fracture response and thus the failure behavior of the water-saturated PAR composites can be restored by drying. This fact indicates that the water absorption and desorption are of a purely physical nature, i.e. they are reversible processes. It was established that chopped fiber-reinforced PAR composites fail by matrix deformation along with fiber/matrix debonding in the crack initiation, whereas fiber pull-out becomes dominant in the crack propagation range. Water uptake shifts both the AE amplitude and energy curves toward lower values, a phenomenon attributed to plastification of the PAR matrix by water.

Key words

acoustic emission failure fracture mechanics hygrothermal aging water uptake 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Karger-Kocsis, J., ‘Microstructure and Fracture Mechanical Performance of Short Fibre Reinforced Thermoplastics’, Ch. 6 in K. Friedrich (ed.),Application of Fracture Mechanics to Composite Materials, Elsevier, Amsterdam, 1989, pp. 189–247.Google Scholar
  2. 2.
    Jinen, E., ‘Acoustic Emission of Single Notched Short Carbon Fiber Reinforced Nylon 6 (FRTP) under Constant Tensile Load’,Eng. Fract. Mech. 21, 1985, 49–61.Google Scholar
  3. 3.
    Choi, N.-S., Takahashi, K. and Hoshino, K., ‘Characteristics of Acoustic Emission During the Damage Process in Notched Short-Fibre-Reinforced Thermoplastics’,NDT& E Int. 25, 1992, 271–278.Google Scholar
  4. 4.
    Bohse, J. and Kroh, G., ‘Micromechanics and Acoustic Emission Analysis of the Failure Process of Thermoplastic Composites’,J. Mater. Sci. 27, 1992, 298–306.Google Scholar
  5. 5.
    Czigány, T. and Karger-Kocsis, J., ‘Comparison of the Failure Mode in Short and Long Glass Fiber-Reinforced Injection-Molded Polypropylene Composites by Acoustic Emission’,Polym. Bull. 31, 1993, 495–501.Google Scholar
  6. 6.
    Friedrich, K. and Karger-Kocsis, J., ‘Fracture and Fatigue of Unfilled and Reinforced Polyamides and Polyester's’, Ch. 5 in J. M. Schultz and S. Fakirov (eds),Solid State Behavior of Linear Polyesters and Polyamides, Prentice Hall, Englewood Cliffs, NJ, 1990, pp. 249–322.Google Scholar
  7. 7.
    Karger-Kocsis, J., Harmia, T. and Czigány, T., ‘Comparison of the Fracture and Failure Behavior of Polypropylene Composites Reinforced by Long Glass Fibers and by Glass Mats’,Comp. Sci. Technol. 54, 1995, 287–298.Google Scholar
  8. 8.
    Mandell, J. F., ‘Fatigue Behavior of Short Fiber Composite Materials’ Ch. 7 in K. L. Reifsnider (ed.),Fatigue of Composite Materials, Elsevier, Amsterdam, 1991, pp. 231–337.Google Scholar

Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • T. Czigány
    • 1
  • Z. A. Mohd Ishak
    • 1
  • J. Karger-Kocsis
    • 1
  1. 1.Institut für Verbundwerkstoffe GmbHUniversity KaiserslauternKaiserslauternGermany

Personalised recommendations