ASTM D7905-2019 pdf free download

ASTM D7905-2019 pdf free download.Standard Test Method for Determination of the Mode II Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
1. Scope
1.1 This test method covers the determination ofthe mode II interlaminar fracture toughness, G IIc , of unidirectional fiber- reinforced polymer matrix composite laminates under mode II shear loading using the end-notched flexure (ENF) test (Fig. 1). 1.2 This method is limited to use with composites consisting of unidirectional carbon-fiber- and glass-fiber-reinforced lami- nates. 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Test Method
4.1 The ENF specimen shown in Fig. 1 consists of a rectangular, uniform thickness, unidirectional laminated com- posite specimen containing a non-adhesive insert at the mid- plane that serves as a delamination initiator. Forces are applied to the specimen through an ENF fixture under displacement controlled loading. 4.2 Delamination growth is not stable in the ENF test. A method is presented so that the initiation values of the mode II interlaminar fracture toughness are obtained from the preim- planted insert as well as from a precrack. 4.3 A record of the applied force versus center roller displacement is to be obtained using an x-y recorder or equivalent real-time plotting device, or else it may be obtained and stored digitally. The mode II interlaminar fracture toughness, G IIc , is obtained using the compliance calibration (CC) method. This is the only acceptable method of data reduction for this test (1). 4 4.4 This standard recommends that static mode II precrack- ing is performed and a recommended method is described. Other precracking methods may be used provided that a record of the shape of the precracked delamination front is obtained prior to the PC test. Precracking methods that typically leave crack front markings for post-test evaluation of these values include mode I and fatigue mode II.
5. Significance and Use
5.1 Susceptibility to delamination is one ofthe 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 ofspecimen geometry or method of force introduction is useful for estab- lishing 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 pro- cessing and environmental variables on G IIc of a particular composite material; 5.2.2 To compare quantitatively the relative values of G IIc for composite materials with different constituents; 5.2.3 To compare quantitatively the values of G IIc obtained from different batches of a specific composite material, for example, to use as a material screening criterion or to develop a design allowable; and 5.2.4 To develop delamination failure criteria for composite damage tolerance and durability analyses.