PSI - Issue 71

M Mohan Kumar et al. / Procedia Structural Integrity 71 (2025) 372–379

375

Fig. 4. Loads and boundary condition.

3.5 Material Properties Composite laminate is made up of 16 layers of CFRP AS4/914, lamina of thickness 0.21mm following stacking sequence [+45/-45/0/0/90/45/0/0] S . The laminate properties are tabulated in the Table 1.

Table 1. Material Properties of AS4/914

E 2 (GPa)

E 3 (GPa)

G 12 (GPa)

G 23 (GPa)

G 31 (GPa)

ν 12

ν 23

ν 21

E 1 (GPa)

130

10

10

5

5

5

0.34

0.33

0.33

The strength of a composite can be expressed by an arbitrarily large number of values, depending on the complexity of the failure criterion. The strength of the material can therefore be represented by five independent variables and as shown below Table 2.

Table 2. Strength Properties of Laminate

X t (MPa)

X c (MPa)

Y t (MPa)

Y c (MPa)

S (MPa)

1300

1000

98

215

65

The adhesive used for the scarf repair was Redux 319A which is a high-performance modified epoxy film adhesive curing at 175°C. Adhesive properties and allowable stresses are tabulated as shown Table 3.

Table 3. Adhesive Properties of Redux 319A

ν

X (MPa)

Y (MPa)

S (MPa)

E (MPa)

3000

0.3 30

30

30

4. Numerical Analysis Numerical analysis in Finite Element Method (FEM) involves applying computational techniques to solve complex structural problems by breaking down a system into discrete finite elements. This approach models material behavior under various conditions, offering detailed insights into stress, strain, and deformation, which are crucial for design and optimization. In this study, the composite laminate consists of 16 layers of CFRP AS4/914 in a quasi-isotropic stacking sequence, with each lamina 0.21 mm thick are modelled as shown in Fig. 5. The properties of both the laminate and adhesive materials are listed below. For the scarf repair, Redux 319A, a high-performance epoxy adhesive, was utilized. The adhesive properties are essential for ensuring the structural integrity of the repaired panel under tensile loads. The bond interface between the scarf patch and the parent laminate was numerically modeled using an explicit adhesive layer (Redux 319A) with material properties provided in Table 3. This adhesive layer was assigned a uniform thickness of 0.2 mm and meshed consistently with adjacent composite plies to maintain continuity and eliminate mesh incompatibility. Perfect bonding was assumed between the adhesive and the composite interfaces by applying bonded contact conditions in ANSYS, which ensures full displacement compatibility and stress transfer across the patch interface. This modeling approach allows accurate evaluation of the bonding efficiency and its contribution to the global load-carrying behavior of the repaired panel.