Significance and Use
5.1 Advanced composite systems are used in a number of applications as shields to prevent penetration by projectiles. In general, the use of composites is more effective for blunt, rather than sharp, projectiles or in hybrid systems in which an additional shield can be used to blunt a sharp projectile. Knowledge of the penetration impact resistance of different material systems or the effects of environmental or in-service load exposure to the penetration resistance of given materials is useful for product development and material selection.
5.2 An impact test used to measure the penetration resistance of a material can serve the following purposes:
5.2.1 To quantify the effect of fiber architecture, stacking sequence, fiber and matrix material selection, and processing parameters on the penetration resistance of different composite materials;
5.2.2 To measure the effects of environmental or in-service load exposure on the penetration impact resistance of a given material system; and
5.2.3 As a tool for quality assurance requirements for materials designed for penetration resistance applications.
5.3 The penetration resistance values obtained with this test method are most commonly used in material specification and selection and research and development activities. The data are not intended for use in establishing design allowables, as the results are specific to the geometry and physical conditions tested and are not generally scalable to other configurations.
5.4 The reporting section requires items that tend to influence the penetration resistance of material systems. These include the following: fiber and matrix materials, fiber architecture, layup sequence, methods of material fabrication, environmental exposure parameters, specimen geometry and overall thickness, void content, specimen conditioning, testing environment and exposure time, specimen fixture and alignment, projectile mass and geometry, and projectile orientation at impact. Additional reporting requirements include size and description of damage, results of any pre- and post-test nondestructive inspection, impact velocity, accuracy of the velocity measurement apparatus, and whether or not the projectile penetrated the panel. Residual velocity is a desirable, but not a necessary, value to be reported.
5.5 The reporting section shall also include the parameters of a statistical function that gives the probability of penetration as a function of impact kinetic energy (see 14.4).
5.6 The relevant measurements that result from the impact test are the kinetic energy and impact velocity of the projectile and whether or not the projectile penetrated the specimen. An optional item to be measured is the loss in kinetic energy of the projectile as a function of impact velocity if measurements of the residual velocity are recorded.
Scope
1.1 This test method measures the resistance of flat composite panels in one specific clamping configuration to penetration by a blunt projectile in free flight. In this test method, the term “penetration” is defined as the case in which the projectile travels completely through the composite panel and fully exits the back side. The composite materials may be continuous fiber angle-ply, woven or braided fiber-reinforced polymer matrix composites, or chopped fiber-reinforced composites. The resistance to penetration is quantified by a statistical function that defines the probability of penetration for a given kinetic energy.
1.2 This test method is intended for composite test panels in which the thickness dimension is small compared with the test panel width and length (span to thickness on the order of 40 or greater).
1.3 This test method is intended for applications such as jet engine fan containment, open rotor engine blade containment, or other applications in which protection is needed for projectiles at velocities typically lower than seen in ballistic armor applications. The typical impact velocity that this test is intended for is in the range of 100 m/s to 500 m/s [300 ft/s to 1500 ft/s], as opposed to higher velocities associated with armor penetration.
1.4 A flat composite panel is fixed between a circular-shaped clamping fixture and a large base fixture each with a large coaxial hole defining a region of the panel that is subjected to impact in the direction normal to the plane of the flat panel by a blunt projectile. Clamping pressure is provided by 28 through bolts that pass through the front clamp, the test specimen, and the back plate. The mass, geometry, desired impact kinetic energy, and impact orientation of the projectile with respect to the panel are specified before the test. Equipment and procedures are required for measuring the actual impact velocity and orientation during the test. The impact penetration resistance can be quantified by either the velocity or kinetic energy required for the projectile to penetrate the test panel fully. A number of tests are required to obtain a statistical probability of penetration for given impact conditions.
1.5 This test method measures the penetration resistance for a specific projectile and test configuration and can be used to screen materials for impact penetration resistance, compare the impact penetration resistance of different composite materials under the same test geometry conditions, or assess the effects of in-service or environmental exposure on the impact penetration resistance of materials.
1.6 The impact penetration resistance is highly dependent on the test panel materials and architecture, projectile geometry and mass, and panel boundary conditions. Results are not generally scalable to other configurations but, for the same test configurations, may be used to assess the relative impact penetration resistance of different materials and fiber architectures.
1.7 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. Within the text the inch-pound units are shown in brackets.
1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
