More D Knowledge of the damage resistance and damage tolerance properties of a laminated composite plate is useful for product development and material selection. 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 generally not scalable to other configurations. Its usefulness in establishing quality assurance requirements is also limited, due to the inherent variability of induced damage, as well as the dependency of damage tolerance response upon the pre-existent damage state. However, it must be understood that the damage tolerance of a composite structure is highly dependent upon several factors including geometry, stiffness, support conditions, and so forth.
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A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. Scope 1. The composite material forms are limited to continuous-ber reinforced polymer matrix composites, with the range of acceptable test laminates and thicknesses dened in 8. The potential energy of the drop-weight, as dened by the mass and drop height of the impactor, is specied prior to test.
Equipment and procedures are provided for optional measurement of contact force and velocity during the impact event. The damage resistance is quantied in terms of the resulting size and type of damage in the specimen. Quasi-static indentation per Test Method D may be used as an alternate method of creating damage from an out-of-plane force and measuring damage resistance properties. Thus, results are generally not scalable to other congurations, and are particular to the combination of geometric and physical conditions tested.
Within the text the inch-pound units are shown in brackets. Combining values from the two systems may result in nonconformance with the standard. 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.
Referenced Documents 2. Current edition approved April 1, Published April Terminology 3. Terminology D denes terms relating to plastics. Terminology E 6 denes terms relating to mechanical testing. Terminology E and Practice E dene terms relating to statistics. In the event of a conict between terms, Terminology D shall have precedence over the other standards.
Use of these symbols is restricted to analytical dimensions when used with square brackets, as the symbols may have other denitions when used without the brackets. The dent depth shall be dened as the maximum distance in a direction normal to the face of the specimen from the lowest point in the dent to the plane of the impacted surface that is undisturbed by the dent.
Tolerances may be applied to a nominal value to dene an acceptable range for the property. Anisotropic materials do not have a principal material coordinate system due to the total lack of symmetry, while, for isotropic materials, any coordinate system is a principal material coordinate system.
In laminated composites, the principal material coordinate system has meaning only with respect to an individual orthotropic lamina. One of the reference coordinate system axes normally the Cartesian x-axis is designated the reference axis, assigned a position, and the ply principal axis of each ply in the laminate is referenced relative to the reference axis to dene the ply orientation for that ply.
Summary of Test Method 4. Damage is imparted through out-of-plane, concentrated impact perpendicular to the plane of the laminated plate using a drop weight with a hemispherical striker tip. The damage response is a function of the test conguration; comparisons cannot be made between materials unless identical test congurations, test conditions, and so forth are used.
Signicance and Use 5. Knowledge of the damage resistance properties of a laminated composite plate is useful for product development and material selection. The damage response parameters can include dent depth, damage dimensions, and through-thickness locations, F1, Fmax, E1 and Emax, as well as the force versus time curve.
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 signicantly larger than the test specimen, Copyright ASTM International Reproduced by IHS under license with ASTM No reproduction or networking permitted without license from IHS which tends to divert a greater proportion of the impact energy into elastic deformation.
In this case, the testing organization should subject several specimens, or a large panel, to multiple low velocity impacts at various impact energy levels using this test method. A relationship between impact energy and the desired damage parameter can then be developed. Subsequent drop weight impact and compressive residual strength tests can then be performed using specimens impacted at an interpolated energy level that is expected to produce the desired damage state.
Interferences 6. Therefore, all deviations from the standard test conguration shall be reported in the results. Important aspects of plate specimen preparation that contribute to data scatter include thickness variation, out-of-plane curvature, surface roughness, and failure to maintain the dimensions specied in 8.
The degree of laminate orthotropy can strongly affect the damage formation. Results can be affected if the impact force is not applied perpendicular to the plane of the laminated plate.
Errors can result if the test specimen and specimen support xture are not centered with respect to the impact device. The second source of force oscillations is the exural vibration of the impacted specimen. The high-frequency ringing oscillations do not typically represent an actual force transmitted to the specimen. However, the oscillations caused by specimen motion are actual forces applied to the specimen and should not be ltered or smoothed.
For both sources, the oscillations are typically excited during initial contact and during damage formation. Results are also affected by wave propagation and vibrations in the specimen, impactor, impact device and support xture during the impact event.
Rather, F1 and E1 represent the initial value of force and energy at which a change in the stiffness characteristics of the specimen can be detected, respectively.
Apparatus 7. A caliper of suitable size shall be used for measurement of dimensions for detected damage. For typical specimen geometries, an instrument with an accuracy of For specimens intended to undergo subsequent residual strength testing, specimen length and width measurements shall use micrometers to ensure consistent measurement accuracy for both test methods.
The cut-out in the plate shall be 75 6 1 mm by 6 1 mm [3. The face of the plate shall be at to within 0. Guiding pins shall be located such that the specimen shall be centrally positioned over the cut-out. Four clamps shall be used to restrain the specimen during impact. The clamps shall have a minimum holding capacity of N lbf. The tips of the clamps shall be made of neoprene rubber with a durometer of Shore A. NOTE 2—When impacted with the standard impactor dened in 7.
Should the expected damage area exceed this size such as in studies for barely visible impact damage, for example , it is recommended to examine alternative specimen and xture designs, such as NASA , which are larger and can accommodate larger damage areas without signicant interaction from edge support conditions. If a different impactor is used as part of the testing, the shape, dimensions and mass shall be noted and the results reported as non-standard.
NOTE 3—If the desired impact energy level cannot be achieved using the standard impactor mass dropped from a height of at least mm [12 in. At a minimum, the impact device shall include a rigid base, a drop-weight impactor, a rebound catcher and a guide mechanism.
The rebound catcher is typically an inertially activated latch that trips upon the initial impact, then catches the impactor on a stop during its second decent. The rebound catcher must not affect the motion of the impactor until after the impactor has lost contact with the specimen after the initial impact. If such equipment is unavailable, rebound hits may be prevented by sliding a piece of rigid material wood, metal, and so forth between the impactor and specimen, after the impactor rebounds from the specimen surface after impact.
More complex devices may include latching and hoist mechanisms, stop blocks or shock absorbers, and instrumentation for determining impactor velocity and impact force.
The use of velocity and force instrumentation is 6 The sole source of this apparatus is available from Carr Lane Manufacturing Co. Box , St. Your comments will receive careful consideration at a meeting of the responsible technical committee,1 which you may attend. Box , Troy, MI The height of the guide mechanism shall be sufficient to permit drop-weight testing for the impact desired energy level. For cylindrical drop tubes, the clearance between the impactor and tube inner diameter should not exceed 1 mm [0.
Details of the guide mechanism geometry shall be noted. In all respects, guide friction shall be negligible; otherwise, velocity measurements shall be required and impact energy calculations shall be based upon the measured velocity Eq 4. Commonly, such systems use a double-pronged ag, which obstruct a light beam between a photo-diode emitter and detector. The ag prongs shall be positioned such that velocity measurement is completed between 3 to 6 mm [0.
The impact velocity is calculated using the measured time the light beam is obstructed by each prong, as well as the time that an impact force is rst detected. Chamber conditions shall be monitored either on an automated continuous basis or on a manual basis at regular intervals.
This chamber shall be capable of maintaining the test specimen at the required test environment during the mechanical test. Equipment capable of recording force and velocity data is required if those measurements are desired.
The natural frequency of the transducer-impactor assembly shall be greater than 6 kHz, the analog-to-digital converter shall be 8-bit or greater, the minimum sampling rate shall be kHz, and the data storage capacity shall be points or larger.
The measuring probe shall have a spherical tip with a maximum radius of curvature of 8. An instrument with an accuracy of mm [ Sampling and Test Specimens 8. For statistically signicant data the procedures outlined in Practice E should be consulted.
The method of sampling shall be reported. Recommended layups for various nominal cured ply thicknesses are provided in Table 1. Fabric laminates containing satin-type weaves shall have symmetric warp surfaces, unless otherwise specied and noted in the report.
Recommended layups for various nominal cured ply thicknesses are provided in Table 2. Tests conducted using alternative stacking sequences must be designated as such, with the stacking sequence recorded and reported with any test results.
Impacting a larger panel can help relieve interaction between the edge conditions and the damage creation mechanisms. Improper ber alignment will affect the measured properties. Erratic ber alignment will also increase the coefcient of variation.
Report the panel fabrication method. The coefficient of variation for thickness measurements taken in Take precautions when cutting specimens from large panels to avoid notches, undercuts, rough or uneven surfaces, or delaminations due to inappropriate machining methods. Obtain nal dimensions by water-lubricated precision sawing, milling, or grinding. The use of diamond-tipped tooling as well as water-jet cutting has been found to be extremely effective for many material systems.
ASTM D7136 Low Velocity Impact
More D Scope 1. The composite material forms are limited to continuous-fiber reinforced polymer matrix composites, with the range of acceptable test laminates and thicknesses defined in 8. The potential energy of the drop-weight, as defined by the mass and drop height of the impactor, is specified prior to test. Equipment and procedures are provided for optional measurement of contact force and velocity during the impact event. The damage resistance is quantified in terms of the resulting size and type of damage in the specimen.
A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. Scope 1. The composite material forms are limited to continuous-ber reinforced polymer matrix composites, with the range of acceptable test laminates and thicknesses dened in 8. The potential energy of the drop-weight, as dened by the mass and drop height of the impactor, is specied prior to test. Equipment and procedures are provided for optional measurement of contact force and velocity during the impact event. The damage resistance is quantied in terms of the resulting size and type of damage in the specimen.