5.1 This test method is designed to produce membrane compressive property data for material specifications, research and development, quality assurance, and structural design and analysis. Factors that influence the compressive response and should therefore be reported include the following: material, methods of material and specimen preparation, specimen conditioning, environment of testing, specimen alignment, speed of testing, time at reinforcement. Properties, in the test direction, that may be obtained from this test method include:5.1.1 Ultimate compressive strength,5.1.2 Ultimate compressive strain,5.1.3 Compressive (linear or chord) modulus of elasticity, and5.1.4 Transition strain.1.1 This test method covers the in-plane compressive properties of polymer matrix composite materials reinforced by high-modulus fibers in a sandwich beam configuration. The composite material forms are limited to continuous-fiber composites of unidirectional orientation. This test procedure introduces compressive load into a thin skin bonded to a thick honeycomb core with the compressive load transmitted into the sample by subjecting the beam to four-point bending.1.2 This procedure is applicable primarily to laminates made from prepreg or similar product forms. Other product forms may require deviations from the test method.1.3 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.1.3.1 Within the text the inch-pound units are shown in brackets.NOTE 1: Additional procedures for determining compressive properties of polymer matrix composites may be found in Test Methods D3410/D3410M and D695.1.4 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.

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5.1 Susceptibility to delamination is one of the major design concerns for many advanced laminated composite structures. Knowledge of a laminated composite material’s resistance to interlaminar fracture is useful for product development and material selection. Furthermore, a measurement of the mode II interlaminar fracture toughness that is independent of specimen geometry or method of force introduction is useful for establishing design allowables used in damage tolerance analyses of composite structures. Knowledge of both the non-precracked and precracked toughnesses allows the appropriate value to be used for the application of interest.5.2 This test method can serve the following purposes:5.2.1 To establish quantitatively the effect of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on GIIc of a particular composite material;5.2.2 To compare quantitatively the relative values of GIIc for composite materials with different constituents;5.2.3 To compare quantitatively the values of GIIc obtained from different batches of a specific composite material, for example, to use as a material screening criterion or to develop a design allowable; and5.2.4 To develop delamination failure criteria for composite damage tolerance and durability analyses.1.1 This test method covers the determination of the mode II interlaminar fracture toughness, GIIc, of unidirectional fiber-reinforced polymer matrix composite laminates under mode II shear loading using the end-notched flexure (ENF) test (Fig. 1).FIG. 1 ENF Test Fixture and Specimen Nomenclature1.2 This method is limited to use with composites consisting of unidirectional carbon-fiber- and glass-fiber-reinforced laminates. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types and classes of composite materials; however, certain interferences have been noted (see Section 6).1.3 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.1.3.1 Within the text the inch-pound units are shown in brackets.1.4 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.1.5 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.

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5.1 Susceptibility to delamination is one of the major design concerns for many advanced laminated composite structures. Knowledge of a laminated composite material's resistance to interlaminar fracture is useful for product development and material selection. Furthermore, a measurement of the mode I interlaminar fracture toughness that is independent of specimen geometry or method of force introduction is useful for establishing design allowables used in damage tolerance analyses of composite structures. Knowledge of both the non-precracked and precracked toughness allows the appropriate value to be used for the application of interest.5.2 This test method can serve the following purposes:5.2.1 To establish quantitatively the effect of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on GIc of a particular composite material;5.2.2 To compare quantitatively the relative values of GIc for composite materials with different constituents;5.2.3 To compare quantitatively the values of GIc obtained from different batches of a specific composite material, for example, to use as a material screening criterion or to develop a design allowable; and5.2.4 To develop delamination failure criteria for composite damage tolerance and durability analyses.1.1 This test method describes the determination of the opening mode-I interlaminar fracture toughness, GIc, of unidirectional fiber-reinforced polymer matrix composite laminates using the double cantilever beam (DCB) specimen (Fig. 1).FIG. 1 Double Cantilever Beam Specimen1.2 This test method is limited to use with composites consisting of unidirectional carbon-fiber and glass-fiber-reinforced laminates with brittle or tough single-phase polymer matrices. This limited scope reflects the experience gained in round-robin testing. This test method may prove useful for other types and classes of composite materials; however, certain interferences have been noted (see 6.6).1.3 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.1.3.1 Within the text, the inch-pound units are shown in brackets.1.4 This standard may involve hazardous materials, operations, and equipment.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.

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5.1 Susceptibility to delamination is one of the major weaknesses of many advanced laminated composite structures. Knowledge of a laminated composite material's resistance to interlaminar fracture under fatigue loads is useful for product development and material selection. Furthermore, a measurement of the relationship of the mode I cyclic strain energy release rate and the number of cycles to delamination growth onset, G–N, that is independent of specimen geometry or method of load introduction, is useful for establishing design allowables used in damage tolerance analyses of composite structures made from these materials. 5.2 This test method can serve the following purposes: 5.2.1 To establish quantitatively the effects of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on G–N of a particular composite material. 5.2.2 To compare quantitatively the relative values of G–N for composite materials with different constituents. 5.2.3 To develop criteria for avoiding the onset of delamination growth under fatigue loading for composite damage tolerance and durability analyses. 1.1 This test method determines the number of cycles (N) for the onset of delamination growth based on the opening mode I cyclic strain energy release rate (G), using the Double Cantilever Beam (DCB) specimen shown in Fig. 1. This test method applies to constant amplitude, tension-tension fatigue loading of continuous fiber-reinforced composite materials. When this test method is applied to multiple specimens at various G-levels, the results may be shown as a G–N curve, as illustrated in Fig. 2. FIG. 1  DCB Specimen with Piano Hinges FIG. 2  G–N Curve 1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with single-phase polymer matrices. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types and classes of composite materials, however, certain interferences have been noted (see Section 6.5 of Test Method D5528). 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3.1 Exception—The values provided in parentheses are for information only. 1.4 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. 1.5 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.

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5.1 Susceptibility to delamination is one of the major weaknesses of many advanced laminated composite structures. Knowledge of the interlaminar fracture resistance of composites is useful for product development and material selection. Since delaminations can be subjected to and extended by loadings with a wide range of mode mixtures, it is important that the composite toughness be measured at various mode mixtures. The toughness contour, in which fracture toughness is plotted as a function of mode mixtures (see Fig. 3), is useful for establishing failure criterion used in damage tolerance analyses of composite structures made from these materials.FIG. 3 Mixed-Mode Summary Graph5.2 This test method can serve the following purposes:5.2.1 To establish quantitatively the effects of fiber surface treatment, local variations in fiber volume fraction, and processing and environmental variables on Gc of a particular composite material at various mode mixtures,5.2.2 To compare quantitatively the relative values of Gc versus mode mixture for composite materials with different constituents, and5.2.3 To develop delamination failure criteria for composite damage tolerance and durability analyses.5.3 This method can be used to determine the following delamination toughness values:5.3.1 Delamination Initiation—Two values of delamination initiation shall be reported: (1) at the point of deviation from linearity in the load-displacement curve (NL) and (2) at the point at which the compliance has increased by 5 % or the load has reached a maximum value (5%/max) depending on which occurs first along the load deflection curve (see Fig. 4). Each definition of delamination initiation is associated with its own value of Gc and GII/G calculated from the load at the corresponding critical point. The 5%/Max Gc value is typically the most reproducible of the three Gc values. The NL value is, however, the more conservative number. When the option of collecting propagation values is taken (see 5.3.2), a third initiation value may be reported at the point at which the delamination is first visually observed to grow on the edge of the specimen. The VIS point often falls between the NL and the 5%/Max points.FIG. 4 Load-Displacement Curves5.3.2 Propagation Option—In the MMB test, the delamination will grow from the insert in either a stable or an unstable manner depending on the mode mixture being tested. As an option, propagation toughness values may be collected when delaminations grow in a stable manner. Propagation toughness values are not attainable when the delamination grows in an unstable manner. Propagation toughness values may be heavily influenced by fiber bridging which is an artifact of the zero-degree-type test specimen (3-5). Since they are often believed to be artificial, propagation values must be clearly marked as such when they are reported. One use of propagation values is to check for problems with the delamination insert. Normally, delamination toughness values rise from the initiation values as the delamination propagates and fiber bridging develops. When toughness values decrease as the delamination grows, a poor delamination insert is often the cause. The delamination may be too thick or deformed in such a way that a resin pocket forms at the end of the insert. For accurate initiation values, a properly implanted and inspected delamination insert is critical (see 8.2).5.3.3 Precracked Toughness—Under rare circumstances, toughness may decrease from the initiation values as the delamination propagates (see 5.3.2). If this occurs, the delamination should be checked to ensure that it complies with the insert recommendations found in 8.2. Only after verifying that the decreasing toughness was not due to a poor insert, should precracking be considered as an option. With precracking, a delamination is first extended from the insert in Mode I, Mode II, or mixed mode. The specimen is then reloaded at the desired mode mixture to obtain a toughness value.1.1 This test method covers the determination of interlaminar fracture toughness, Gc, of continuous fiber-reinforced composite materials at various Mode I to Mode II loading ratios using the Mixed-Mode Bending (MMB) Test.1.2 This test method is limited to use with composites consisting of unidirectional carbon fiber tape laminates with brittle and tough single-phase polymer matrices. This test method is further limited to the determination of fracture toughness as it initiates from a delamination insert. This limited scope reflects the experience gained in round robin testing. This test method may prove useful for other types of toughness values and for other classes of composite materials; however, certain interferences have been noted (see Section 6). This test method has been successfully used to test the toughness of both glass fiber composites and adhesive joints.1.3 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 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.1.5 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.

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