Abstract:In order to investigate the performance of the adhesive bonding repair in composite structures, static tensile test is carried out on the bonding structures numerically and experimentally. The tensile stress–displacement behaviors of T7901 composite adhesive bonding structure is studied under room temperature. Based on the three-dimensional progressive damage theory, the model of adhesive bonding structures with different patch shape has been constructed, and the final failure strength is predicted using APDL … Show more
“…It is generally expected that the shape of the repair patch as well as its thickness have an effect on strength recovery. 31 For instance, thicker patches will lead to higher failure loads. 32,33 Figure 13.Strength of open-hole and repaired samples from configuration shown in Figure 5 for UD, PW, and TW laminates.…”
Section: Resultsmentioning
confidence: 99%
“…It is generally expected that the shape of the repair patch as well as its thickness have an effect on strength recovery. 31 For instance, thicker patches will lead to higher failure loads. 32,33 Upon investigating the failure surfaces for repaired samples, similar failure modes were generally observed for both repair methods, explaining the similar strength values presented in Figure 13.…”
Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs.
“…It is generally expected that the shape of the repair patch as well as its thickness have an effect on strength recovery. 31 For instance, thicker patches will lead to higher failure loads. 32,33 Figure 13.Strength of open-hole and repaired samples from configuration shown in Figure 5 for UD, PW, and TW laminates.…”
Section: Resultsmentioning
confidence: 99%
“…It is generally expected that the shape of the repair patch as well as its thickness have an effect on strength recovery. 31 For instance, thicker patches will lead to higher failure loads. 32,33 Upon investigating the failure surfaces for repaired samples, similar failure modes were generally observed for both repair methods, explaining the similar strength values presented in Figure 13.…”
Ultrasonic welding is a common fusion bonding technique to join unreinforced and reinforced thermoplastics. It is expected that applying ultrasonic vibrations to thermoset prepregs can produce heat generation to promote resin flow and consolidation. This paper discusses the feasibility of using ultrasonic vibrations as a high-speed repair technique for carbon fiber/epoxy prepregs to replace the traditional vacuum-bagging scarf setup. Three material types were investigated: out-of-autoclave unidirectional and plain weave prepregs (Cycom® 5320) and a general purpose twill weave prepreg (AS4/Newport 301). Two welding modes were considered: time and travel (vibrations stop once the desired vertical displacement is reached). For each mode, vibration time, travel, force, and amplitude were investigated. Cross-sectional analysis showed that void content equal to or below the vacuum-bagged samples could be achieved with ultrasonic consolidation to meet aerospace standards (≤2%). The following ultrasonic parameters were recommended to preserve prepreg tows integrity and minimize void content: vibration time below 1.0 s, travel between 12.5% and 50% of sample's initial thickness, force equal to or below 100 N, and amplitude below 41.3 μm. Temperature values recorded during the ultrasonic process reached the manufacturer's cure temperature range (120℃ to 180℃), with a predicted maximum degree of cure of 0.24. Interlaminar shear strength values were comparable for ultrasonically consolidated and vacuum-bagged samples. Soft and hard repair patches were applied to open-hole tensile coupons, with up to 50% strength recovery for both repair methods. Overall, ultrasonic consolidation has potential as a time- and cost-efficient repair method for thermoset prepregs.
“…For thin sheets, the one-sided patch is useful but for thicker plates, it has less effect. 33 In Li et al., 34 the effect of patch shape on the repair efficiency was investigated, and it was observed that the square patch has a better performance than other patches. In Mhamdia et al., 35 by examining the effect of the patch shape on the repair performance in aerospace structures, it was concluded that the rectangular shape performance can be improved by using H-shape and the H-shape performance will be improved by the arrow shape (Figure 5).…”
Section: The Effect Of the Patch Adhesive And Main Plate Geometry Onmentioning
In many industries, when replacement of a part is not possible or economic, the repair is done. One of the best methods for repairing metal and composite parts is using composite patches. Repairing with a composite patch is a widespread field to extend the service life of the cracked components. This technique is more structurally efficient with fewer damages on the structure than others. The bonded patch offers many advantages over a mechanically fastened doubler, which include improved fatigue behavior, reduced corrosion, and easy conformance to complex aerodynamic contours. In this article, advantages of the composite patch and its efficiency and durability are discussed, and the most important parameters (patch and adhesive thickness, patch separation, residual stress, patch length and width, etc.) affecting its performance are studied based on the latest available references.
“…The effect of intralaminar damage can be taken into account by reducing the stiffness coefficients. Here, we adopt the model shown in equation (13) to compute the degradation of coefficients of the stiffness matrix. The relation between the effective stressp and the nominal stress isp…”
Section: Cohesive Zone Model For the Interlaminar And Bonding Interfamentioning
confidence: 99%
“…[10][11][12] The tensile stress-displacement behaviors of T7901 composite adhesive bonding structure was studied under room temperature. 13 Vaidya et al 14 found that the out-of-plane load causes higher peel stress concentration than in-plane load, and adhesive crack mode is the first mixture mode that then transforms into pure mode II. Hence, out-of-plane load (three-point bending (3pb) and fourpoint bending (4pb)) is worth to be studied deeply and systematically.…”
Due to the high connecting strength and excellent load-transferring efficiency, the adhesively stepped-lap composite bonding has been widely used as joints and repairs in advanced aircraft structures. In the service life of composite structures, they frequently subject to bending loads which are rarely reported by the available reference. Hence, in this paper, three-point and four-point bending experiments are performed on composite stepped-lap structures. Typical damage mode of adhesive on the stepped surface has been found in experiments. And the failure of composite fiber, matrix, interlamination and adhesive materials appeared as competitive behavior. Furthermore, numerical models of stepped-lap composite joints, which used cohesive zone model and 3D Hashin criteria to simulate the inter- and intralaminar damages, were utilized to predict the bending strength and progressive damage. The FEM model, based on progressive damage method, captured the detailed failure as the loading displacement was increasing. The simulation results of load displacement and damage have good agreement with the experiments.
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