Co-cured joint

Fig. 1. Cure cycle for the manufacturing process of the co-cured joint.

Figure 1 shows the cure cycle for the co-cured lap joints and table 1 shows the material properties of the carbon fiber-epoxy composite (USN 150) produced by SK Chemicals (Suwon, Korea). After the curing and bonding processes, the co-cured joint should be finished using various abrasive sandpapers to obtain a better joint strength by eliminating sharp edges. A... 

Consohdate as many substructures as possible, co-cure adhesive bonded assemblies, and build in stiffeners. This is the primary method of reducing costs. (Co-curing is not universally accepted in the industry due to the inability to perform an inspection on the co-cured joint and the possible cost ramifications if the joint is found to be defective.)... 

Composites Both UV and EB cures are employed for the production of wood composite materials and in fiber-reinforced composites for aircraft and aerospace applications. The EB technology has been successful in the manufacture of large structures that exceed the size of autoclaves, and in curing adhesive joints in cases where uniform radiation can be provided more easily than uniform heat. In industrial and consumer applications, multiple combinations of different reinforcing fibers can be co-cured in one cycle by EB with considerably lower residual stresses than those introduced by thermal cure.16... 

Electrolyte 0.3% KC1 aq. solution prepared with twice-distilled water, containing 0.02 M benzotriazole. Polarization Cathodic 5 V for 10 min and 10 min without potential (with air bubbling). Joints were tested after 24 h in boiling water. Adhesive 100 parts diglycidyl ether of bisphenol A (Epon 828 from Shell Chemical Co.) cured with four parts dicyandiamide at 175DC for 2 h. 

BOND PARAMETERS AFFECTING FAILURE OF CO-CURED SINGLE AND DOUBLE LAP JOINTS SUBJECTED TO STATIC AND DYNAMIC TENSILE LOADS... 

Co-cured lap joints, surface roughness, stacking sequence, manufacturing pressure, tensile load bearing capacity, fatigue characteristics. 

Fig. 2. Photograph of the co-cured lap joint specimens, (a) Co-cured single lap joint (b) co-cured double lap joint.

Bond Parameters Affecting Failure of Co-Cured Single and Double Ixtp Joints... 

In the case of the dynamic tensile test, co-cured single lap joint specimens selected in this paper... 

The bond length of the specimens under cyclic tensile test was 20mm. Cyclic tensile tests were performed under the condition of stress ratio 7 = 0.1 and a loading frequency / = 5 Hz. Cyclic tensile loads applied to the co-cured single lap joint specimens were 30%, 40%, 50%, 60%, and 70% of the tensile load bearing capacity obtained from the static tensile load test. 

EXPERIMENTAL RESULTS OF THE CO-CURED LAP JOINTS UNDER STATIC TENSILE LOADS... 

Figure 4 shows typical failure surfaces obtained from tensile tests of the co-cured single and double lap Joint specimens. In the case of the co-cured single lap Joint, as the surface preparation on the steel adherend is better, a greater amount of carbon fibers and epoxy resin is attached to the steel adherend. Failure mechanism is a partial cohesive failure mode at the C ply of the composite adherend. In contrast with the co-cured single lap joint, failure mechanism of the co-cured double lap joint is the partial cohesive failure or interlaminar delamination failure at the 1 ply of the composite adherend because interfocial out-of-plane peel stress... 

Tensile load bearing capacities of the co-cured lap joints with respect to the... 

In this study, residual thermal stresses were also eonsidered because co-cured lap joints generally undergo temperature drop (from 120D to 20D) during the curing process. The stress distributions in the co-cured single and double lap joints were analyzed using ABAQUS i.8 to be commercial finite element analysis software [21],... 

Fig. 8. Coordinate system of the co-cured single and double lap joints for calculating stress distributions in the ply-axis.

The co-cured single and double lap joints were modeled as a three-dimensional solid structure. The resin layer was ignored in this analysis because the average thickness of the resin layer... 

Fig. 10. Interfacial out-of-plane transverse stress distribution, a , of the co-cured single lap joint along the interface between steel and composite adherends. (a) [0]32t stacking sequence and (b) [ 45]4s s stacking sequence.

Fig. 11. Interfacial out-of-plane shear stress distribution, a , of the co-cured single lap joint...

Figures 12 and 13 show interfacial out-of-plane transverse and shear stress distributions of the co-cured double lap joints with [0]i6t and [ 45]4s stacking sequences along the interfaces between steel and composite adherends, respectively. It is important to consider interfacial out-of-plane shear stress rather than interfacial out-of-plane transverse stress because of the compressive stress distribution due to the symmetric configuration of the co-cured double lap...

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