ASTM-D5961:2010 Edition(Redline)

This test method is designed to produce bearing response data for material specifications, research and development, quality assurance, and structural design and analysis. The standard configuration for each procedure is very specific and is intended primarily for development of quantitative double- and single-shear bearing response data for material comparison and structural design. Procedures A and D, the double-shear configurations, with a single fastener loaded in shear and reacted by laminate tension or compression, are particularly recommended for basic material evaluation and comparison. Procedures B and C, the single-shear, single- or double-fastener configurations are more useful in evaluation of specific joint configurations, including fastener failure modes. The Procedure B 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 (although tensile loading is permitted). The Procedure C specimen is particularly well-suited for development of countersunk-fastener bearing strength data where a near-double-shear fastener rotational stiffness is desired. These Procedure B and C configurations have been extensively used in the development of design allowables data.

It is important to note that these four procedures, using the standard test configurations, will generally result in bearing strength mean values that are not of the same statistical population, and thus not in any way a “ basic material property. ”

Note 2—Typically, Procedure D will yield slightly higher strengths than Procedure A (due to the finite edge distance, e , in Procedure A); while Procedure C will yield significantly higher strengths than Procedure B (due to the larger fastener rotation and higher peak bearing stress in Procedure B). For protruding head fasteners, Procedure D will typically yield somewhat higher results than Procedure C (due to both stress peaking and finite edge distance in Procedure C), and Procedures A and C yield roughly equivalent results.

It is also important to note that the parameter variations of the four procedures (tabulated in Section 4) 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 these variations makes meaningful comparison between datasets difficult if the datasets were not tested using the same procedure and identical test parameters.

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 at temperature, void content, and volume percent reinforcement.

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

Ultimate bearing strength, F ^bru , of the composite laminate or laminate-fastener joint, or both;

Offset bearing strength, F ^bro , of the composite laminate or laminate-fastener joint, or both; and

Bearing stress/bearing strain curve.

1. Scope

1.1 This test method covers the bearing response of pinned or fastened joints using multi-directional polymer matrix composite laminates reinforced by high-modulus fibers by double-shear tensile loading (Procedure A), single-shear tensile or compressive loading of a two-piece specimen (Procedure B), single-shear tensile loading of a one-piece specimen (Procedure C), or double-shear compressive loading (Procedure D). Standard specimen configurations using fixed values of test parameters are described for each procedure. However, when fully documented in the test report, a number of test parameters may be optionally varied. 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.

1.2 This test method is consistent with the recommendations of MIL-HDBK-17, which describes the desirable attributes of a bearing response test method.

1.3 The multi-fastener test configurations described in this test method are similar to those used by industry to investigate the bypass 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. Note that the scope of this test method is limited to bearing and fastener failure modes. Use Test Method D7248/D7248M for by-pass testing.

1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

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 and health practices and determine the applicability of regulatory limitations prior to use.

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 D953 Test Method for Bearing Strength of 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 D3410/D3410M Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by Shear Loading 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 D7248/D7248M Test Method for Bearing/Bypass Interaction Response of Polymer Matrix Composite Laminates Using 2-Fastener Specimens 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 E238 Test Method for Pin-Type Bearing Test of Metallic Materials E456 Terminology Relating to Quality and Statistics E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases

Other Document

MIL-HDBK-17, Polymer Matrix Composites, Vol 1, Section 7 Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://dodssp.daps.dla.mil.

Keywords

bearing properties; bearing strength; composite mat