Abstract:Complex composite structures manufactured using a low-pressure vacuum bag-only (VBO) method are more susceptible to defects than flat laminates because of the presence of complex compaction conditions at corners. This study investigates the contribution of multivariate processing parameters such as bagging techniques, curing profiles, and laminate structures on laminates’ shape conformation. Nine sets of laminates were produced with a concave corner and another nine sets with a convex corner, both with a 45° i… Show more
“…It can be observed that the 60° mold resulted in larger thickness variation than 30° mold in both concave and convex molds. Compare with previous research with similar part geometry, 13 their result showed that CTD was from 3.2% to 13.1%, which showed that the corner thickness deviation was inevitable during the process.Figure 10.Corner thickness deviation of the laminate in (a) 30° mold (b) 60° mold.…”
Section: Resultsmentioning
confidence: 55%
“…The curing process is also a critical procedure, including bagging arrangement, frequency of debulking, curing profile, and types of caul plate. Mujahid et al 13 reported that the bagging techniques and cure cycles were the main parameters affecting the void content. Hu and Nutt 14 investigated the effects of debulk temperature on inter-ply air removal and gas permeability of VBO prepregs.…”
This study used the vacuum bag-only process to fabricate angle composite parts on a complex-shape mold by employing interleaved unidirectional prepreg and dry fiber. The study focuses on the thickness variation along the angle part by analyzing the thickness distribution within the angle part by the statistic method. The corner thickness deviation (CTD) and angle deviation (AD) of the angle part were used to quantify the quality of the part by different process parameters and mold design. The results indicated that the CTD and AD were both linearly decreased with the increase of the part thickness. Besides, the part fabricated with the convex mold presented higher dimensional stability and uniformity as compared to that with the concave mold. In addition, we investigated the effect of caul plate applied at the corner regions, and the results showed that the lead caul plate could effectively improve the thickness change in the corner area in both the concave and convex mold. In order to fully understand the thickness variation of the part at the corner region, a semi-empirical model was proposed to forecast the corner thickness deviation of angle part. In this study, the prediction errors of the semi-empirical model for the parts by the concave and convex molds are 10% and 25%, respectively.
“…It can be observed that the 60° mold resulted in larger thickness variation than 30° mold in both concave and convex molds. Compare with previous research with similar part geometry, 13 their result showed that CTD was from 3.2% to 13.1%, which showed that the corner thickness deviation was inevitable during the process.Figure 10.Corner thickness deviation of the laminate in (a) 30° mold (b) 60° mold.…”
Section: Resultsmentioning
confidence: 55%
“…The curing process is also a critical procedure, including bagging arrangement, frequency of debulking, curing profile, and types of caul plate. Mujahid et al 13 reported that the bagging techniques and cure cycles were the main parameters affecting the void content. Hu and Nutt 14 investigated the effects of debulk temperature on inter-ply air removal and gas permeability of VBO prepregs.…”
This study used the vacuum bag-only process to fabricate angle composite parts on a complex-shape mold by employing interleaved unidirectional prepreg and dry fiber. The study focuses on the thickness variation along the angle part by analyzing the thickness distribution within the angle part by the statistic method. The corner thickness deviation (CTD) and angle deviation (AD) of the angle part were used to quantify the quality of the part by different process parameters and mold design. The results indicated that the CTD and AD were both linearly decreased with the increase of the part thickness. Besides, the part fabricated with the convex mold presented higher dimensional stability and uniformity as compared to that with the concave mold. In addition, we investigated the effect of caul plate applied at the corner regions, and the results showed that the lead caul plate could effectively improve the thickness change in the corner area in both the concave and convex mold. In order to fully understand the thickness variation of the part at the corner region, a semi-empirical model was proposed to forecast the corner thickness deviation of angle part. In this study, the prediction errors of the semi-empirical model for the parts by the concave and convex molds are 10% and 25%, respectively.
“…Referring to composite materials, several manufacturing technologies can be highlighted, such as hand laminating, vacuum bagging [ 4 ], infusion [ 5 ], pultrusion [ 6 , 7 ], and filament winding [ 8 , 9 , 10 , 11 ]. Those processes allow manufacturers to provide the very complex material geometries and structures used in many modern applications.…”
Fire resistance is a major issue concerning composite materials for safe operation in many industrial sectors. The design process needs to meet safety requirements for buildings and vehicles, where the use of composites has increased. There are several solutions to increasing the flame resistance of polymeric materials, based on either chemical modification or physical additions to the material’s composition. Generally, the used flame retardants affect mechanical properties either in a positive or negative way. The presented research shows the influence of the mixed-mode behavior of epoxy resin. Fracture toughness tests on epoxy resin samples were carried out, to investigate the changes resulting from different inorganic filler contents of aluminum trihydroxide (ATH). Three-point bending and asymmetric four-point bending tests, with different loading modes, were performed, to check the fracture behavior in a complex state of loading. The results showed that the fracture toughness of mode I and mode II was reduced by over 50%, compared to neat resin. The experimental outcomes were compared with theoretical predictions, demonstrating that the crack initiation angle for higher values of KI/KII factor had a reasonable correlation with the MTS prediction. On the other hand, for small values of the factor KI/KII, the results of the crack initiation angle had significant divergences. Additionally, based on scanning electron microscopy images, the fracturing of the samples was presented.
Process parameters for vacuum‐bag‐only (VBO) method are of critical importance to control manufacturing‐induced void content and mechanical properties of laminated composites. Currently, no comparative studies are readily available on various VBO processing parameters namely bagging techniques, cure cycles, and laminate thicknesses on induced defects and mechanical properties. Hence, this study investigates the effects of these parameters on manufacturing‐induced void content and mechanical properties of composite laminates. Laminate samples were manufactured using L27 Taguchi orthogonal array experimental plan. Void contents, tensile and flexural properties of these samples were evaluated. Double VBO technique and direct (modified) cure cycle were found to be the most promising parameters in achieving the lowest void content among choices of bagging techniques and cure cycles, respectively. However, improved mechanical properties were achieved using a single VBO technique due to the higher fiber reinforcement volume fraction. In comparison to a typical cure cycle, the modified cure cycles were able to reduce surface porosity and through‐thickness void by 48.33% and 23.7%, respectively, whereas the tensile and flexural properties were increased by 2% to 3% and 17% to 20%, respectively. In addition, no significant interaction between parameters was observed.
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