Face sheet materials were first ground with 180 grade sandpaper in accordance with the 3M 2216 adhesive user instructions, and then the aluminum plates were cleaned with acetone, while the composite plates were cleaned with isopropyl alcohol.

Jen et al. indicated that an 0.7 kg/m² amount of adhesive achieved maximum flexural strength ¹⁶; therefore, 7.5 g of adhesive, corresponding to that amount, was applied to the cleaned side of the face sheet materials with a spatula. After applying adhesive to a single face, the samples were kept under a 2.5 kg weight for 24 hours, and then adhesive was applied to the other face. Before performing tests, all specimens were left at room temperature for 1 week to ensure completion of the adhesive curing process.

The mechanical properties of the 3M 2216 adhesive, and the Al-5754 and Al-3003 alloys are shown in Table 2, while the mechanical properties of the CFRP composite are shown in Table 3. E₁ and E₂ are the longitudinal and transverse elastic modulus, ν₁₂ is Poisson’s ratio, G₁₂ is the shear modulus, and X^T and X^C are longitudinal tensile and compressive strengths, respectively. X^C, Y^C and S are longitudinal compressive strength, transverse compressive strength and shear strength, respectively.

Table 2. Mechanical properties of the adhesive, and the Al-5754 and Al-3003 alloys