Significance and Use
Susceptibility to damage from concentrated indentation forces is one of the major weaknesses of many structures made of advanced laminated composites. Knowledge of the damage resistance of a laminated composite material subjected to a concentrated indentation force is useful for product development and material selection.
The QSI test method can serve the following purposes:
5.2.1 To establish quantitatively the effects of stacking sequence, fiber surface treatment, variations in fiber volume fraction, and processing and environmental variables on the damage resistance of a particular composite laminate to a concentrated quasi-static indentation force.
5.2.2 To compare quantitatively the relative values of the damage resistance parameters for composite materials with different constituents. The damage response parameters include d, F1, and Fmax, as well as the F/δ curve.
5.2.3 To place a controlled amount of damage in a specimen for subsequent damage tolerance tests.
5.2.4 To isolate and measure the indentation response of the specimen without bending (rigidly backed configuration).
1.1 A quasi-static indentation (QSI) test method is used to obtain quantitative measurements of the damage resistance of a continuous-fiber-reinforced composite material to a concentrated indentation force (Fig 1). The indentation force is applied to the specimen by slowly pressing a hemispherical indenter into the surface. Procedures are specified for determining the damage resistance for a simply supported test specimen and for a rigidly backed test specimen. The damage resistance is quantified in terms of a critical contact force associated with a single event or sequence of events to cause a specific size and type of damage in the specimen. These tests may be used to screen materials for damage resistance or to inflict damage into a specimen for subsequent damage tolerance testing. This test method is limited to use with composites consisting of layers of unidirectional fibers or layers of fabric. This test method may prove useful for other types and classes of composite materials. Certain interferences, however, have been noted (see 6.7).
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information purposes only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.