Information on the most widely used ASTM standards within the materials testing industry
ASTM D8336 Standard Test Method for Characterizing Tack of Prepregs Using a Continuous Application-and-Peel Procedure
This test method covers measurement of adhesion (tack) between partially cured (B-staged) composite prepreg and a substrate in a peel test, under specified conditions. The test may be conducted to measure tack between a flexible layer of prepreg and another prepreg layer bonded to a rigid substrate (Method I) or a rigid metal substrate (Method II). This test method is primarily geared towards material characterization for automated material layup but can be modified for use with other processes. It is well known that material tack is a function of multiple processing and environmental variables. Permissible composite prepreg materials include carbon, glass, and aramid fibers within a B-staged thermoset resin.
1, Characterizing tack for different prepreg materials, test parameters, surface combinations, and environmental conditions provides insight for optimizing process parameters (particularly deposition rate and deposition temperature) for industrial automated material placement processes.
2, Results obtained through employing the continuous application-and-peel method, as described in studies (1-3),3 reflect the effects of adhesion forming between prepreg layers or between prepreg and metal substrate, and loss of cohesion within the resin in the prepreg, upon tack. This test method allows the adhesive properties of B-staged resin to be explored in a manner relevant for dynamic material deposition processes, where timescales for bonding of prepreg to the substrate or previously placed prepreg layers are short prior to curing. In contrast, Test Methods D3167 and D1781 determine the peel resistance of adhesive bonds for adhesion measurement and process control of laminated or bonded adherends.
3, The test method is suitable to quantify tack of prepregs for acceptance and process control and can be extended to determine resin shelf life or to adjust process parameters to resin out-time. Direct comparison of different resins/prepreg or processes can only be made when specimen preparation and test conditions are identical.

What is the ASTM D8336 prepreg adhesion peel test?
ASTM D8336 prepreg adhesion peel test is a standard test method for characterizing the viscosity of prepregs, measuring the adhesion between the prepreg and the surface through a continuous peel procedure. This test is suitable for evaluating the surface tackiness of thermosetting resin prepregs (such as carbon fiber, glass fiber, etc.) in a partially cured state, primarily used for material analysis in automated layup processes.
Scope of application:
applicable for measuring the viscosity between flexible prepreg layers and rigid substrates (such as metals or rigid materials), particularly suitable for material acceptance and quality control in Automated Fiber Placement (AFP) and Automated Tape Laying (ATL) processes.
Testing principle:
A constant peel force is applied to separate the prepreg layer from the substrate, measuring the viscosity index related to the required peel force and the sample width. Test results are influenced by pressure, temperature, and humidity and must be conducted under specified conditions.
Testing method:
Using a floating roller peel device, the prepreg layer is wound around a rotating drum while a constant peel force is applied. The required force during the peeling process is measured to evaluate viscosity. This method quantifies the initial viscosity of the prepreg and the effects of the curing process on viscosity.
Deep guide for the composite prepreg tack peeling test ASTM D8336
The ASTM D8336 peel adhesion test method for prepreg composites materials is primarily used to characterize the adhesion between the prepreg and the substrate by measuring the adhesive force through a continuous coating and peeling procedure.
The following are key testing points:
1, Testing Equipment and Material Preparation- Equipment:
A dedicated continuous application-peel testing fixture is required, which includes a peel roller with a diameter of 25mm and a rigid compaction roller.
2, Sample Size: The length of the prepreg samples should be ≥ 215mm, width recommended is 75mm; the size of the metal substrate is 140×80×0.8mm (stainless steel 2B finish).
3, Substrate Treatment: For testing the prepreg-metal substrate, the substrate surface must be cleaned with acetone.Testing Procedure
4, Calibration of the pressing force: Set to 100N (for a 75mm sample width).
5, Sample Clamping: Center the sample/substrate assembly in the fixture, bending the protective film around the peel roller and clamping tightly.
6, Environmental Control: The environmental chamber should be controlled to an accuracy of ±1°C, and humidity must be recorded.
7, Start Testing: Move the crosshead at a constant speed, with a data acquisition rate of ≥ 10Hz, and record the displacement-load curve.
8, Data Analysis:
The adhesive force calculation formula is: Ft = F2 - F1
where F1 is the average force during the protective film peeling stage, and F2 is the average force during the prepreg adhesion stage.
Notes
The test must record material information (resin system, fiber type, batch number) and test parameters (temperature, humidity, pressing force, peeling rate).Data should include the average force of the two stages and the standard deviation.
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