Standard Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a Concentrated Quasi-Static Indentation Force

Importancia y uso:

5.1 Susceptibility to damage from concentrated out-of-plane forces is one of the major design concerns of many structures made of advanced composite laminates. Knowledge of the damage resistance properties of a laminated composite plate is useful for product development and material selection.

5.2 QSI testing can serve the following purposes:

5.2.1 To simulate the force-displacement relationships of impacts governed by boundary conditions (1-7).5 These are typically relatively large-mass low-velocity hard-body impacts on plates with a relatively small unsupported region. Since the test is run slowly in displacement control, the desired damage state can be obtained in a controlled manner. Associating specific damage events with a force during a drop-weight impact test is often difficult due to the oscillations in the force history. In addition, a specific sequence of damage events may be identified during quasi-static loading while the final damage state is only identifiable after a drop-weight impact test.

5.2.2 To provide an estimate of the impact energy required to obtain a similar damage state for drop-weight impact testing if all others parameters are held constant.

5.2.3 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 indentation force.

5.2.4 To compare quantitatively the relative values of the damage resistance parameters for composite materials with different constituents. The damage response parameters can include dent depth, damage dimensions and through-thickness locations, F_max , E_a, and E_max, as well as the force versus indenter displacement curve.

5.2.5 To impart damage in a specimen for subsequent damage tolerance tests, such as Test Method D7137/D7137M.

5.2.6 To measure the indentation response of the specimen with and without bending using the two specimen configurations (edge supported and rigidly backed).

5.3 The properties obtained using this test method can provide guidance in regard to the anticipated damage resistance capability of composite structures of similar material, thickness, stacking sequence, etc. However, it must be understood that the damage resistance of a composite structure is highly dependent upon several factors including geometry, thickness, stiffness, mass, support conditions, etc. Significant differences in the relationships between force/energy and the resultant damage state can result due to differences in these parameters. For example, properties obtained using the specimen supported over a circular hole would more likely reflect the damage resistance characteristics of an un-stiffened monolithic skin or web than that of a skin attached to sub-structure which resists out-of-plane deformation. Similarly, test specimen properties would be expected to be similar to those of a panel with equivalent length and width dimensions, in comparison to those of a panel significantly larger than the test specimen, which tends to divert a greater proportion of the energy into elastic deformation.

5.4 The standard indenter geometry has a blunt, hemispherical tip. Historically, for the standard laminate configuration, this indenter geometry has generated a larger amount of internal damage for a given amount of external damage than is typically observed for similar indenters using sharp tips. Alternative indenter geometries may be appropriate depending upon the damage resistance characteristics being examined. For example, the use of sharp tip geometries may be appropriate for certain damage visibility and penetration resistance assessments.

5.5 Some testing organizations may desire to use this test method in conjunction with Test Method D7137/D7137M to assess the compression residual strength of specimens containing a specific damage state, such as a defined dent depth, damage geometry, etc. In this case, the testing organization should subject several specimens to multiple energy or force levels using this test method. A relationship between energy or force and the desired damage parameter can then be developed. Subsequent QSI and compression residual strength tests can then be performed using specimens indented at an interpolated energy or force level that is expected to produce the desired damage state.

Subcomité:

D30.05

Referida por:

D7956_D7956M-16R24, D7137_D7137M-23, D7136_D7136M-20, D4762-23, D7766_D7766M-23

Volúmen:

15.03

Número ICS:

83.120 (Reinforced plastics)

Palabras clave:

composite materials; damage resistance; delamination; dent; impact; quasi-static indentation;