Deviation-Rectifying Control of Carbon Fiber Prepreg Slitting and Winding Machine

With the growing needs of prepreg tapes for the automated fiber placement(AFP),the deviation-rectifying of prepreg in slitting process was investigated on a self-developed 16-tow prepreg slitting and winding machine.The process of slitting and rewinding of prepreg tape was introduced,and the reason of prepreg tape deviation in slitting process was analyzed.In order to ensure the quality of the narrow prepreg slits,the application of the fuzzy PID algorithm in a closed-loop control system was discussed.A fuzzy PID algorithm was designed by combining fuzzy rules and PID controller.By applying it to precise deviation-rectifying control strategy,the automatic control of rectification could be achieved with accuracy of 0.1 mm,which satisfies the requirement of the prepreg tape both in slitting quality and layup quality for AFP.

Mechanical Properties of Carbon Epoxy Prepreg Insert Phenolic Resin Injection Moldings

This study focuses on the insert-injection molding process. The thermoset composite inserts in this study were carbon fiber/epoxy (CF/Epoxy) prepreg sheets. The injected molded part was glass fiber contained phenolic resin (GF/PF). The CF/Epoxy was placed in the mold cavity prior to injecting GF/PF onto the inserted injection molded CF/Epoxy specimens. The role of adhesion between the inserted part and injected resin on the mechanical properties was evaluated by 3 point bending and impact tests. In addition, the effect of prepreg orientation on the mechanical properties of the prepreg inserted-injection molding system was investigated. It was found that the prepreg with unidirectional orientation significantly improved flexural and impact strength of the inserted injection molding composites, providing better support and resistance to bending and impact loading. The main failure modes of the specimens were structural and adhesive failure.

流变仪在覆铜板工序中的应用

本文简要叙述利用流变仪对覆铜箔层压板生产工序中的胶液和半固化片参数进行控制,从而更好地保证胶液和 半固化片性状的一致性,以有利于控制板材流胶和品质。

Composite materials for primary aircraft structures:from development phase to high volume production rate

From 1980’s decade,the introduction of carbon composite materials in structural applications has been consistently increased in the successive generations of civil aircraft from Single Aisle to Middle-long Range to achieve a culminant point with more than 50%in structure weight in recent commercial civil aircraft.This evolution,done through successive iterations,has been possible by combining in the same time the improvement of intrinsic composite material performances and its transformation into prepreg production technologies together with the development of new manufacturing process for material lay-up automation at composite shop-floor manufacturer of aircraft composite parts.New challenges are still coming to continuously develop materials and technologies in order to pursue the production more cost-effective composite parts.Associated to higher aircraft production rate for single aisle,new challenges may force material and aircraft designers and producers to furthermore drive new products and processes introduction and new ways of transformation within in next decade of composite aircraft designs.We propose to illustrate these trends using past and recent developments and our return of experience from Hexcel on Civil Aircraft programs.

Effects of Lay-up Types of Out-of-autoclave Prepregs on Preparation Quality of L-shape Composite Laminates

Effects of layer quantities and stacking sequences on L-shape composite manufacturing qualities in using OOA(out-of-autoclave)prepregs were studied.The mechanisms of air evacuated in 5 kinds of lay-ups were revealed by image analysis of cut surfaces and thickness measurements.Results show that air in OOA prepregs is evacuated in two ways.Most of the air is forced out of layers directly by vacuum before air accesses in prepregs closed.Very little entrapped air moves perpendicularly to outer layers under hydrostatic resin pressure.When a laminate contains less than 16 layers,voids can hardly be found in layers.When a laminate contains more than 16 layers,voids cannot be expelled completely during the window of vertical movement.As for stacking sequences,the synergetic effect of slip function and nest function determines the thickness and voids content of laminates.Results show that the average of single layer thickness of unidirectional layers is the lowest,and the average of single layer thickness of quasi-isotropic layers is the highest.The voids content of quasi isotropic is the highest,which is consistent with the theoretical analysis.

Resin Content Monitoring Technique for Film Impregnation Process

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Investigation of the Flexural Properties and Failure Behavior of Unidirectional CF/Nylon 6 and CF/Epoxy Composites

In this work, flexural properties and failure behavior of unidirectional (UD) carbon fiber reinforced polyamide 6 (CF/Nylon 6) and epoxy resin (CF/ Epoxy) laminates were investigated through three-point bending test. The mechanical properties and failure behavior of 0 and 90 degree CF/Nylon 6 and CF/Epoxy laminates were discussed based on the fiber volume fraction, fiber distribution, void content, interfacial properties, transversal tensile strength and fracture toughness. The effects of fiber volume fraction, fiber distribution, void content and their hybrid effect on the flexural properties were investigated. Step-by-step observation and scanning electron microscope observation of laminates after flexural tests were employed to analyze the fracture process.

Associations of Prepregnancy Body Mass Index,Gestational Weight Gain,and Intelligence in Offspring:A Systematic Review and Meta-Analysis

Objective:Increasing evidences have shown that prepregnancy maternal weight and gestational weight gain(GWG)may associate with offspring’s neurodevelopment.However,the effects of prepregnancy maternal overweight,obesity,and excessive GWG on offspring’s intelligence remain controversial.This meta-analysis aimed to re-assess the association between prepregnancy body mass index(BMI),GWG,and children’s intelligence.Methods:We systematically searched multiple databases,including PubMed,EMBASE,Cochrane Library,and Ovid Medline,from their inception through February 2021.Studies assessing the association between prepregnancy BMI or GWG and children’s intelligence were further screened manually before final inclusion.Cohorts that analyzed the association between prepregnancy BMI or GWG and intelligence of offspring were included,and we used the Mantel-Haenszel fixed-effects method to compute the weighted mean difference(WMD)and 95%confidence interval(CI)of each study.Results:A total of 12 articles were included in this systematic review,while six of them in the meta-analysis.There was a significant full-scale IQ reduction in children born from overweight and obese mothers,with WMDs of-3.08(95%CI:-4.02,-2.14)and-4.91(95%CI:-6.40,-3.42),respectively.Compared with control group,the WMDs for performance and verbal intelligence quotient(IQ)were decreased in overweight and obesity groups.However,we observed no association between children’s full-scale IQ and excessive GWG with WMD of-0.14(95%CI:-0.92,0.65).Conclusions:Women’s prepregnancy overweight and obesity adversely associate with children’s intelligence but no association with excessive GWG.Our study suggests that further researches focusing on the effect of prepregnancy maternal health on offspring’s intelligence development are needed.

A shortcut to marking 3D target curves on curved surface via a galvanometric laser scanner

Marking arbitrary three-dimensional(3D) target curves on given objects with curved surface is required in many industrial fields, such as fabric prepreg placement in composite material part fabrication, product assembly, surface painting for decoration, etc. A shortcut to the solution of this intractable problem is proposed by utilizing a galvanometric laser scanner(GLS) with the aid of a camera. Without using the existing tedious GLS calibration procedures,the proposed method directly establishes a mapping between the 3D coordinates of the laser spots on the object surface and the control voltages of the scanner. A single-hidden layer feedforward neural network(SLFN) is employed to model the mapping. By projecting a dense grid of laser spots on the object to be marked and simultaneously taking only one image, the SLFN model is trained in minutes via a linear solving mechanism. Experiments demonstrate that the trained SLFN model has a good generalization performance for marking 3D target curves. The 3D laser marking errors on experimental objects are less than 0.5 mm. The proposed method is especially suitable for on-site use and can be conveniently extended to multiple GLSs for marking large complex objects.