PurposeThe purpose of this paper is to present a comparative study, regarding cooling time and dimensional accuracy, of conventional injection mold cooling channel layouts, using straight holes and a baffle, and free‐form fabricated (FFF) layout, manufactured by the direct‐metal rapid tooling (RT) method electron beam melting (EBM). Many other methods have been proven useful for RT, but the authors have not found any publications where EBM has been used to manufacture injection molding tools.Design/methodology/approachA test part was designed in order to replicate a common and important issue: inadequate cooling in deep cores. The part and the different cooling layouts were analyzed in an injection molding simulation software and the numerical results were compared with corresponding experimental results.FindingsThe analyses showed an improvement in both cooling time and dimensional accuracy in favor of conformal FFF cooling channels manufactured by EBM. The experimental results correlate well with the numerical tests, however with some discrepancies.Research limitations/implicationsThe results presented are based on the direct‐metal RT method EBM, and they were obtained using a specific test part.Originality/valueThis paper can be a useful aid when designing mold tools and especially when considering the usage of FFF cooling channels versus conventional cooling design. It can also serve as a reference when comparing the efficiency in terms of cooling time and dimensional accuracy between different layouts.
Delamination fatigue crack growth experiments were carried out on unidirectional T300/914 C Graphite/Epoxy laminates. Both mode I and mixed mode (mode I and mode II in combination) situations were investigated for the stress ratios R = 0.1, 0.3 and 0.5. Double Cantilever Beam (DCB) specimens were used for the pure mode I tests and Cracked Lap Shear (CLS) specimens were used for the mixed mode tests. The initial delaminations were produced by inserting 0.03 mm thick PTFE films during laminate layup. The cyclic loading of the specimens was carried out at a frequency of 5 Hz and with a constant stress ratio maintained throughout the test. It was found that the mode I cyclic crack growth rate yielded a power law relationship between da/dN and the cyclic variation in the energy release rate ΔGI. This relation was virtually independent of the stress ratio, at least for 0.1 < R < 0.5. The mixed mode results showed a similar power law relation between da/dN and Δ(G I + GII). Here a small stress ratio dependence was observed. The data were fitted to two alternative power law crack growth relations. Knowing the ratio of GIlGII and with the assumption that the mode I and mode II contributions of crack growth were additive, it was possible to formulate a crack growth relationship of:
The efficiency of different melt impregnation methods for producing continuous glass fiber–polypropylene tapes has been evaluated. The selected methods were the common pin assisted method, a crosshead impregnation die including different vibration techniques and a slit die. The degree of melt impregnation was studied qualitatively with optical microscopy and determined quantitatively by opacity measurements. Excellent results were obtained using the radial slit die, followed by the pin chamber impregnation method. The crosshead impregnation die gave poor impregnation. With the radial slit die it was possible to achieve high fiber volume fraction and it was easy to control the fiber–matrix content. The haul off speed ranged from 1–10 m/min.
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