Search

Void defect is prevalent during the composite manufacturing process and may reduce the mechanical properties of composite structures, while limited information about three‐dimensional void distribution and evolution can be found due to the difficulties in void observation. In this work, void defects at different positions were detected and analyzed using x‐ray microtomography (XRM), and the random forest algorithm was implemented for segmenting components of CFRP samples. Results showed a trend of gradual rising porosity in the axial direction, with an increase of ~250% of porosity at the outlet of resin injection compared to the one at the inlet during the composite manufacturing process. The voids mainly featured with microscale between carbon fibers, with less distribution between fiber bundles and resin‐rich zones. Void defects achieved aggregation at the middle position of manufactured laminate, which is probably related to pressure interception. In the axial direction, the proportion of large‐diameter voids gradually increased, and a large volume of connected voids appeared near the outlet. Due to the shear deformation of resin and fiber and the pressure gradient effect, most of the voids showed stripe shape. The spatial orientation of voids was predominantly along the direction of resin flow and fluctuated due to fiber curl. Highlights: 3D void characteristics in CFRP were studied using the XRM technique.Void formation and the effects of fibers on void morphology were analyzed.Dynamic void transport mechanisms during CFRP manufacturing were studied.Location and morphology of voids are helpful for CFRP damage modeling.The effective partitioning of CFRP was achieved using a random forest algorithm. [ABSTRACT FROM AUTHOR]

To address the issues of probiotic activity loss during storage and feeding, as well as the limited efficacy of single probiotics, a solution was devised by embedding a mixture of Bacillus coagulans SN‐8 (SN‐8) and Saccharomyces boulardii SN‐6 (SN‐6) in a gel. The initial step involved screening the probiotic microcapsules' preparation method and wall material. Using sodium alginate and β‐cyclodextrin as composite wall material and chitosan as the outer coating material allowed for an embedding rate of 82.11% in composite probiotic microcapsules prepared by the air atomization method. Next, in vitro, simulated digestion experiments were conducted to determine the number of viable bacteria and the release rate of the microcapsules. The results showed that compared to the free strain, the mixed probiotic microcapsules retained a survival rate of 67.5% after 3 h of simulated gastric juice exposure and 70.56% after 42 days of storage at 4°C. This demonstrated higher survival rates and storage stability. The prepared probiotic microcapsules were then administered to dairy cows. 16S rDNA gene sequencing showed that consumption of the microcapsules reduced the number of harmful bacteria, such as Paeniclostridium, in the intestinal tract of dairy cows while accelerating the growth of beneficial bacteria, such as Bifidobacterium. In particular, this resulted in a significant improvement in the lactation performance of the cows, with a 4.5% increase in milk fat content, a 92.5% increase in milk protein content, and a 3.5% increase in milk urea nitrogen content (6.75 mL/dL). In conclusion, probiotic microcapsules can effectively regulate intestinal flora, improving milk production, and quality in dairy cows. [ABSTRACT FROM AUTHOR]

Characterizing the interlayer interaction is beneficial to mitigate the manufacturing defects in the multi‐layered fabric forming of composite. However, the interlayer interactions including the force and sliding distance, and their effects on the defect generation have not been reported yet. Here, the monolayer and multi‐layered fabric hemisphere forming were conducted by experiments. Firstly, the forming force and deformation modes at different hemisphere regions are confirmed in the monolayer fabric forming as a reference. Then, in the multi‐layered forming, the interlayer interaction is confirmed to still exist in the configuration with the same ply orientations, whereas the forming force, forming force rate, and interlayer sliding are smaller than that in the configuration with different ply orientations. In addition, with the increase of layer number, the extent of interlayer interaction is improved, which intensifies the defect from the out of plane yarn buckling to the macro wrinkle in the tensile direction. Especially, it is revealed that the tensile direction of lower layer should be avoided under the shear direction of upper layer to reduce the interlayer sliding. These results obtained here provide an important reference to the multi‐layered plain woven fabric forming. [ABSTRACT FROM AUTHOR]

CFRP composites with the advantages of enhanced mechanical properties and lightweight are recognized as an ideal material in repairing cracked structures. This paper aims to comprehensively investigate whole‐field strain distribution and fracture characteristics of central inclined titanium plates repaired with CFRP laminates, with consideration of various overlap length and repair type. Results indicated that the initial central cracks significantly deteriorated mechanical performance, while inclined direction of it exhibited limited influence on repair behavior. Repairs with increased overlap length possessed superior mechanical performance and repair effectiveness. When increasing the overlap length to 80 mm, strength recovery rate for four types of repairs reached above 80.0%. Digital image correlation (DIC) results indicated that central hole was the highly strained zone for all repairs, and hole repairs presented relatively higher strain values compared with cracked repairs. Progressive failure analysis showed that repairs with initial cracks presented premature fracture of titanium plates, while hole repairs were capable to sustain load until adhesive layer fractured. Adhesive failure, cohesive failure and substrate fracture predominated on fractured surfaces irrespective of repair type and overlap length. With the increase of overlap length, cohesive failure was enhanced and light‐fiber‐tear/fiber‐tear could be found, which corresponded to relatively higher repair effectiveness. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber reinforced poly‐ether–ether–ketone (CCF/PEEK) shows great potential in engineering applications attributed to superior mechanical properties together with excellent thermal and chemical resistance. In this study, a laser‐assisted additive manufacturing device was established to accurately collect and control the preheating temperature based on a coaxial infrared temperature measurement system. The influence on laser power consumption, interlaminar shear performance, and failure mechanism was investigated in condition of different preheating temperatures and printing speeds. Results indicated that the laser‐preheated specimens showed much higher ILSS with maximum values and increasing percentage reached 33.48 MPa and 157.0% compared to unpretreated specimens. With the increase of preheating temperature and printing speed, more laser power was consumed, while the ILSS and increasing percentage increased firstly and then decreased. The strengthening effect on the interlayer bonding was ascribed to promoting the penetration of PEEK molecular chain ends between adjacent layers, increasing the fluidity and enhancing the bonding effect between adjacent filament together with improving the impregnation behavior of the inner fibers. The proposed interlaminar strengthening method based on laser‐assisted preheating provides potential application prospects in aerospace and automotive industries. [ABSTRACT FROM AUTHOR]

Crystallization and phase engineering offer a promising route to significantly improve the impact property of long glass fiber‐reinforced polypropylene random copolymer (LGF/PPR) composites. However, the nucleation and crystallization mechanism in the crystallization process, and the resulting phase change mechanism are still unclear, which severely limits the remarkable improvement of the toughness of LGF/PPR composites. Herein, we successfully fabricate toughened LGF/PPR composites with excellent heat deflection temperature and impact toughness via tuning the crystallization behavior and phase structure generated by introducing β‐nucleating agent (β‐NA). Through differential scanning calorimeter and wide‐angle X‐ray diffraction analysis, the influence of LGF and β‐NA on the nucleation and crystallization mechanism of the PPR matrix was revealed. Therefore, the critical crystallization parameters were calculated, and then the correlation was established with tensile and impact properties through regression analysis. The results show that the impact strength of β‐PPR and β‐LGF/PPR/MPPR are remarkably increased by 50.1% and 26.3% at the critical β‐NA content of 0.2 and 0.1 wt%, respectively, due to the intrinsic toughening mechanism. This work may pave the way for preparing a class of LGF/PPR composites with high‐impact toughness. [ABSTRACT FROM AUTHOR]

The strain response and influence of elevated temperature on the viscoelastic behavior of fabric in the compaction process cannot be described and predicted by current viscoelastic models. Here, a viscoelastic model, verified by compaction experiments, is originally proposed to depict the stress and strain responses in different stages of the compaction, especially considering the effects of added binder and elevated temperature. The model effectively captures that with the rising temperature, the interaction among fibers is enhanced due to the fiber volume expansion. Accordingly, the elastic modulus is enlarged in the compression stage. In the relaxation stage, the interaction suppresses the fiber realignment, leading to the reduction of stress relaxation. In the creep stage, the elevated temperature increases the deformation stiffness, indicating the strain is declined. In the relaxation stage, the adhesive effect of added binder facilitates the stress relaxation, and then the increasing stress relaxation promotes the increment of strain in the creep stage. [ABSTRACT FROM AUTHOR]

Objective: To investigate the value of neuron‐specific enolase (NSE), neutrophil‐to‐lymphocyte ratio (NLR) and lymph node metastasis in predicating distant metastasis in patients with limited‐stage small cell lung cancer (LD‐SCLC). Methods: Clinical pathological data of LD‐SCLC patients in the First Affiliated Hospital of Wenzhou Medical University between August 2009 and October 2017 were retrospectively analyzed. The age, gender, smoking, TNM, NSE, NLR, chemotherapy cycle, radiotherapy, surgery and new metastasis of lymph nodes of 47 cases with distant metastasis and 47 cases without distant metastasis in 1 year were compared. Finally, factors influencing distant metastasis were determined as the predictors. The receiver operating characteristic (ROC) curve model was established based on logistic regression analysis of the factors obtained. Results: Distant metastasis mainly involved brain (17/47), liver (17/47) and bone (17/47). Univariate analysis showed that patients with new lymph node metastasis, high NSE, pretreatment hilar lymph node metastasis and NLR were more prone to have distant metastasis. Multivariate analysis showed that new lymph node metastasis, high NSE, NLR and pretreatment hilar lymph node metastasis were independent predictors. The predictive model established using these predictors had an AUC of 0.872 (95%CI: 0.803‐0.941), a sensitivity of 76.60% and a speciality of 80.85%. Conclusion: The new lymph node metastasis, NLR and NSE are predictors of distant metastasis, and thus, may have a profound impact on treatment decision making. Patients with lower NLR and NSE expression levels and less new metastasis of lymph nodes have a lower distant metastasis rate. [ABSTRACT FROM AUTHOR]

High power fiber laser was proved to be feasible to cut carbon fiber reinforced plastic (CFRP) laminate with high efficiency, while the machined quality on mechanical performance was not fully understood. This paper studied the effect of high temperature up to 220°C on tensile strength degradation and strain distribution of unidirectional CFRP laminate with open hole machined with fiber laser. Differential scanning calorimetry (DSC) was firstly employed to determine the glass transition temperature (Tg) of polymer‐matrix composite. Digital image correlation technique was applied to evaluate whole‐field strain distribution and crack propagation/evolution of CFRP laminate featured with open hole under tensile loading. Results showed that the tensile strength of laser machined CFRP laminate degraded significantly during working in high temperature above 100°C. The value of strains distributed around center hole was highly related to the elevated temperature and applied load levels. Splitting was the prevalent failure mode of CFRP laminate under elevated temperature up to 180°C. Finally, semi‐empirical model was developed for evaluating tensile performance of laser machined CFRP laminate at elevated temperature based on regression analysis. [ABSTRACT FROM AUTHOR]

Long glass fiber‐reinforced polypropylene (LGF/PP) foaming composite has been increasingly used in automotive components regarding its good mechanical and acoustic properties. However, the balance of its mechanical property and acoustic property is far from being understood. The objective of this study is to investigate the influences of molding thickness or foaming degree on both mechanical and acoustic properties of LGF/PP foaming composite by experimental tests. First, LGF/PP foaming composite felts with consistent surface density were fabricated, then specimens with a series of molding thicknesses were prepared by compression molding. Tensile and acoustic tests were conducted and a scanning electron microscopy was also used for analyzing microscopic characteristics. The results indicate that tensile strength and tensile modulus of the present LGF/PP composite decrease in exponential formats, whereas sound absorption coefficients of them increase in logarithmic formats, when molding thickness vary from 1.5 to 8 mm. The above curves intersect around 3 mm. Thus, both mechanical and acoustic properties should be balanced regarding structural size when designing a multi‐purpose vehicle component using the present composite. POLYM. COMPOS., 40:1315–1321, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure. [ABSTRACT FROM AUTHOR]