ASTM D7332 Standard Test Method for Measuring the Fastener Pull-Through Resistance of a Fiber-Reinforced Polymer Matrix Composite

ASTM D7332 Introduction

ASTM D7332 (Standard Test Method for Measuring the Fastener Pull-Through Resistance of a Fiber-Reinforced Polymer Matrix Composite) is a test to determine the ability of composite laminates to resist fastener pull-through during perpendicular loading. The property has a direct impact on joint reliability in the aerospace and structural applications. The method employs two procedures. Procedure A aids in the screening and development of fasteners. Procedure B sets design values that are dependent on the configuration. A test involves pulling a fastener through a plate of composite as the force and displacement are measured. The test assists engineers in understanding failure behavior and in selecting appropriate fasteners for polymer-matrix composite components.

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• Figures out the pull-through resistance of fiber-reinforced composites.
• Coats continuous or discontinuous laminates of fiber.
• The loading is applied perpendicular to simulate the joint conditions.
• Assists in screening as well as in design evaluation.
• Enables the comparison of fastener systems with controlled conditions.

Use of ASTM D7332

• Enables structural design allowances of composite joints.
• Helps in developing and optimizing fasteners.
• Measures the performance of joints when subjected to mechanical loading.
• Helps compare various fastener arrangements.

Why Do Fastener Design Parameters Affect Pull-Through Resistance?

The geometry of fasteners directly impacts the stress in the composite. Reduced compression stress through-thickness is achieved with larger head diameters. Thus, special fasteners enhance joint performance. Results also depend on parameters like hole diameter, torque, and clearance. The proper reporting of these factors will guarantee sound comparisons.

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ASTM D7332 determines the pull-through resistance at controlled loading and at specific settings. Technicians place a composite specimen using a fastener and apply a force perpendicular to the laminate. They measure the force and displacement as long as they do not fail. 

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Specimen Configuration	Symmetric and balanced composite laminates with defined thickness and stacking sequence
Procedure A	Uses a defined loading bar spacing ratio for screening and fastener development
Procedure B	Uses the clearance hole ratio for configuration-specific design evaluation
Compressive-Loaded Fixture	To reduce the loading eccentricity, the setup uses two square plates with rectangular cross-sections, each with a central hole and four peripheral holes. A fastener attaches the plates, which are rotated 45° relative to each other. The applied compressive force causes tensile loading in the fastener.
Tensile-Loaded Fixture	The setup inserts a plate with a central hole into a fixture and secures the fastener with a revolving yoke to prevent loosening. When the system applies tensile force, the fastener carries tensile load, and the plate experiences out-of-plane compression.

ASTM D7332 reports either in SI units or inch-pound units. The values of forces are measured in newtons (N) or pounds-force (lbf). Displacement is in millimeters (mm) or inches. The force-displacement curve is useful for determining the first failure, maximum load, and last rupture. Increased resistance is a sign of improved joint functioning and enhanced suitability of fastener design.

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