ASTM D6415/D6415M-22

Standard Test Method for Measuring the Curved Beam Strength of a Fiber-Reinforced Polymer-Matrix Composite

SIGNIFICANCE AND USE
5.1 Susceptibility to delamination is one of the major design concerns for many advanced laminated composite structures. Complex structural geometries can result in out-of-plane stresses, which may be difficult to analyze. When curved structural details are loaded such that the deformation results in an increase in the radius of curvature, interlaminar tensile stress and delaminations can result. Knowledge of a laminated composite material’s resistance to interlaminar fracture is useful for product development and material selection. Failure criteria and design allowables involving out-of-plane stresses may not be readily available or may be poorly validated, requiring additional experimental data.  
5.2 This test method can serve the following purposes:  
5.2.1 To measure a curved-beam strength;  
5.2.2 To measure an interlaminar strength when using a unidirectional specimen where all fibers are oriented 0° relative to the long straight edges of the specimen;  
5.2.3 To establish quantitatively the effect of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on the curved beam strength or the interlaminar (through-the-thickness) tensile strength of a particular composite material;  
5.2.4 To compare quantitatively the relative curved-beam strength or interlaminar tensile strengths of composite materials with different constituents;  
5.2.5 To compare quantitatively the values of the curved-beam strength or interlaminar tensile strengths obtained from different batches of a specific composite material, for example, to use as a material screening criterion, to use for quality assurance, or to develop a design allowable;  
5.2.6 To produce out-of-plane structural failure data for structural design and analysis; and  
5.2.7 To develop failure criteria for predicting failures caused by out-of-plane stresses.
SCOPE
1.1 This test method determines the curved beam strength of a continuous fiber-reinforced composite material using a 90° curved beam specimen (Figs. 1 and 2). The curved beam consists of two straight legs connected by a 90° bend with a 6.4 mm [0.25 in.] inner radius. An out-of-plane (through-the-thickness) tensile stress is produced in the curved region of the specimen when force is applied. This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers.
FIG. 1 Test Specimen Geometry (SI units)  
FIG. 2 Test Specimen Geometry (inch-pound)  
1.2 This test method may also be used to measure the interlaminar tensile strength if a unidirectional specimen is used where the fibers run continuously along the legs and around the bend.  
1.3 This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers.  
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.

General Information

• Status: Published
• Publication Date: 31-Jan-2022
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.06 - Interlaminar Properties

Relations

• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020

Standards Content (Sample)

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.
Designation: D6415/D6415M − 22
Standard Test Method for
Measuring the Curved Beam Strength of a Fiber-Reinforced
1
Polymer-Matrix Composite
This standard is issued under the fixed designation D6415/D6415M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2
1.1 Thistestmethoddeterminesthecurvedbeamstrengthof 2.1 ASTM Standards:
a continuous fiber-reinforced composite material using a 90° D792Test Methods for Density and Specific Gravity (Rela-
curved beam specimen (Figs. 1 and 2). The curved beam tive Density) of Plastics by Displacement
consists of two straight legs connected by a 90° bend with a D883Terminology Relating to Plastics
6.4mm [0.25 in.] inner radius. An out-of-plane (through-the- D2584Test Method for Ignition Loss of Cured Reinforced
thickness) tensile stress is produced in the curved region of the Resins
specimen when force is applied. This test method is limited to D2734TestMethodsforVoidContentofReinforcedPlastics
use with composites consisting of layers of fabric or layers of D3171Test Methods for Constituent Content of Composite
unidirectional fibers. Materials
D3878Terminology for Composite Materials
1.2 This test method may also be used to measure the
D5229/D5229MTestMethodforMoistureAbsorptionProp-
interlaminar tensile strength if a unidirectional specimen is
erties and Equilibrium Conditioning of Polymer Matrix
used where the fibers run continuously along the legs and
Composite Materials
around the bend.
D5687/D5687MGuide for Preparation of Flat Composite
1.3 This test method is limited to use with composites
Panels with Processing Guidelines for Specimen Prepara-
consisting of layers of fabric or layers of unidirectional fibers.
tion
E4Practices for Force Calibration and Verification of Test-
1.4 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The ing Machines
E6Terminology Relating to Methods of MechanicalTesting
values stated in each system are not necessarily exact equiva-
E18Test Methods for Rockwell Hardness of Metallic Ma-
lents; therefore, to ensure conformance with the standard, each
system shall be used independently of the other, and values terials
E122PracticeforCalculatingSampleSizetoEstimate,With
from the two systems shall not be combined.
1.4.1 Within the text, the inch-pound units are shown in Specified Precision, the Average for a Characteristic of a
Lot or Process
brackets.
E177Practice for Use of the Terms Precision and Bias in
1.5 This standard does not purport to address all of the
ASTM Test Methods
safety concerns, if any, associated with its use. It is the
E456Terminology Relating to Quality and Statistics
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
3.1 Definitions—Terminology D3878 defines terms relating
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard- to high-modulus fibers and their composites. Terminology
D883definestermsrelatingtoplastics.TerminologyE6defines
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- terms relating to mechanical testing. Terminology E456 and
Practice E177 define terms relating to statistics. In the event of
mendations issued by the World Trade Organization Technical
a conflict between terms, Terminology D3878 shall have
Barriers to Trade (TBT) Committee.
precedence over the other terminology standards.
1
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of D30.06 on Interlaminar
2
Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2022. Published April 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1999. Last previous edition approved in 2013 as D6415/ Standards volume information, refer to the standard’s Document Summary page on
D6415M–06a(2013). DOI: 10.1520/D6415_D6415M-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6415/D6415M − 22
3.3.9 l = distance along the sp
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6415/D6415M − 06a (Reapproved 2013) D6415/D6415M − 22
Standard Test Method for
Measuring the Curved Beam Strength of a Fiber-Reinforced
1
Polymer-Matrix Composite
This standard is issued under the fixed designation D6415/D6415M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method determines the curved beam strength of a continuous fiber-reinforced composite material using a 90° curved
beam specimen (Fig. 1Figs. 1 and 2 and Fig. 2). The curved beam consists of two straight legs connected by a 90° bend with a
6.4-mm6.4 mm [0.25 in.] inner radius. An out-of-plane (through-the-thickness) tensile stress is produced in the curved region of
the specimen when force is applied. This test method is limited to use with composites consisting of layers of fabric or layers of
unidirectional fibers.
1.2 This test method may also be used to measure the interlaminar tensile strength if a unidirectional specimen is used where the
fibers run continuously along the legs and around the bend.
1.3 This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text the
inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must
be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
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.
1
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of D30.06 on Interlaminar Properties.
Current edition approved Oct. 1, 2013Feb. 1, 2022. Published October 2013April 2022. Originally approved in 1999. Last previous edition approved in 20062013 as
ε1
D6415 – 06D6415/D6415M – 06aA(2013). . DOI: 10.1520/D6415_D6415M-06AR13.10.1520/D6415_D6415M-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D6415/D6415M − 22
FIG. 1 Test Specimen Geometry (SI units)
FIG. 2 Test Specimen Geometry (inch-pound)
2. Referenced Documents
2
2.1 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
E4 Practices for Force Calibration and Verification of Testing Machines
E6 Terminology Relating to Methods of Mechanical Testing
E18 Test Methods for Rockwell Hardness of Metallic Materials
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
...