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    ASTM D7248 / D7248M - 21

    Standard Test Method for High Bearing - Low Bypass Interaction Response of Polymer Matrix Composite Laminates Using 2-Fastener Specimens

    Active Standard ASTM D7248 / D7248M | Developed by Subcommittee: D30.05

    Book of Standards Volume: 15.03

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    Significance and Use

    5.1 This test method is designed to produce bearing/bypass interaction response data for research and development, and for structural design and analysis. The standard configuration for each procedure is very specific and is intended as a baseline configuration for developing structural design data.

    5.1.1 Procedure A, the bypass/high bearing double-shear configuration is recommended for developing data for specific applications which involve double shear joints.

    5.1.2 Procedure B, the bypass/high bearing single-shear configuration is more useful in the evaluation of typical joint configurations. The specimen may be tested in either an unstabilized (no support fixture) or stabilized configuration. The unstabilized configuration is intended for tensile loading and the stabilized configuration is intended for compressive loading. These configurations, particularly the stabilized configuration, have been extensively used in the development of design allowables data. The variants of either procedure provide flexibility in the conduct of the test, allowing adaptation of the test setup to a specific application. However, the flexibility of test parameters allowed by the variants makes meaningful comparison between datasets difficult if the datasets were not tested using identical test parameters.

    5.2 General factors that influence the mechanical response of composite laminates and should therefore be reported include the following: material, methods of material preparation and lay-up, specimen stacking sequence, specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, speed of testing, time held at test temperature, void content, and volume percent reinforcement.

    5.3 Specific factors that influence the bearing/bypass interaction response of composite laminates and should therefore be reported include not only the loading method (either Procedure A or B) and loading type (tension or compression) but the following (for both procedures): edge distance ratio, width to diameter ratio, diameter to thickness ratio, fastener torque, fastener or pin material, fastener or pin clearance; and (for Procedure B only) countersink angle and depth of countersink, type of grommet (if used), type of mating material, and type of support fixture (if used). Properties, in the test direction, which may be obtained from this test method include the following:

    5.3.1 Filled hole tensile bearing/bypass strength.

    5.3.2 Filled hole compressive bearing/bypass strength.

    5.3.3 Bearing stress/bypass strain curve.

    1. Scope

    1.1 This test method determines the uniaxial bearing/bypass interaction response of multi-directional polymer matrix composite laminates reinforced by high-modulus fibers by either double-shear tensile loading (Procedure A) or single-shear tensile or compressive loading (Procedure B) of a two-fastener specimen. The scope of this test method is limited to net section (bypass) failure modes. Standard specimen configurations using fixed values of test parameters are described for each procedure. A number of test parameters may be varied within the scope of the standard, provided that the parameters are fully documented in the test report. The composite material forms are limited to continuous-fiber or discontinuous-fiber (tape or fabric, or both) reinforced composites for which the laminate is balanced and symmetric with respect to the test direction. The range of acceptable test laminates and thicknesses are described in 8.2.1. Test methods for high bypass - low bearing response of polymer matrix composite materials, previously published under Procedure C of this test method, are now published in Test Method D8387/D8387M.

    1.2 This test method is consistent with the recommendations of Composite Materials Handbook, CMH-17, which describes the desirable attributes of a bearing/bypass interaction response test method.

    1.3 The two-fastener test configurations described in this test method are similar to those in Test Method D5961/D5961M as well as those used by industry to investigate the bearing portion of the bearing/bypass interaction response for bolted joints, where the specimen may produce either a bearing failure mode or a bypass failure mode. Should the test specimen fail in a bearing failure mode rather than the desired bypass mode, then the test should be considered to be a bearing dominated bearing/bypass test, and the data reduction and reporting procedures of Test Method D5961/D5961M should be used instead of those given in this test method.

    1.4 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.

    1.4.1 Within the text, the inch-pound units are shown in brackets.

    1.5 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.

    1.6 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.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

    D883 Terminology Relating to Plastics

    D2584 Test Method for Ignition Loss of Cured Reinforced Resins

    D2734 Test Methods for Void Content of Reinforced Plastics

    D3171 Test Methods for Constituent Content of Composite Materials

    D3878 Terminology for Composite Materials

    D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials

    D5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation

    D5766/D5766M Test Method for Open-Hole Tensile Strength of Polymer Matrix Composite Laminates

    D5961/D5961M Test Method for Bearing Response of Polymer Matrix Composite Laminates

    D6484/D6484M Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates

    D6742/D6742M Practice for Filled-Hole Tension and Compression Testing of Polymer Matrix Composite Laminates

    D8387/D8387M Test Method for High Bypass Low Bearing Interaction Response of Polymer Matrix Composite Laminates

    E4 Practices for Force Verification of Testing Machines

    E6 Terminology Relating to Methods of Mechanical Testing

    E83 Practice for Verification and Classification of Extensometer Systems

    E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process

    E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

    E251 Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages

    E456 Terminology Relating to Quality and Statistics

    E1237 Guide for Installing Bonded Resistance Strain Gages

    ICS Code

    ICS Number Code 59.100.01 (Materials for the reinforcement of composites in general)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/D7248_D7248M-21

    Citation Format

    ASTM D7248 / D7248M-21, Standard Test Method for High Bearing - Low Bypass Interaction Response of Polymer Matrix Composite Laminates Using 2-Fastener Specimens, ASTM International, West Conshohocken, PA, 2021, www.astm.org

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