聚甲基丙烯酰亚胺(PMI)泡沫夹芯复合材料的滚筒剥离性能研究

系统研究了泡沫密度、泡孔孔径、成型方式、芯材或蒙皮表面的糙化处理对聚甲基丙烯酰亚胺(PMI)泡沫夹芯复合材料剥离强度性能的影响。研究结果表明,泡沫密度、泡孔孔径、成型方式和表面糙化对PMI夹芯复合材料的剥离强度提高均有明显作用,其中以泡沫密度和泡孔孔径影响最为显著,分别提高了157%和95%。本研究内容对如何提高PMI泡沫夹芯复合材料的剥离强度具有很好的工艺指导作用。     

Comparison of foam core sandwich panel and through‐thickness polymer pin–reinforced foam core sandwich panel subject to indentation and flatwise compression loadings

Through‐thickness polymer pin–reinforced foam core sandwich (FCS) panels are new type of composite sandwich structure as the foam core of this structure was reinforced with cylindrical polymer pins, which also rigidly connect the face sheets. These sandwich panels are made of glass fiber–reinforced polyester face sheets and closed‐cell polyurethane foam core with cylindrical polymer pins produced during fabrication process. The indentation and compression behavior of these sandwich panels were compared with common traditional sandwich panel, and it has been found that by reinforcing the foam core with cylindrical polymer pins, the indentation strength, energy absorption, and compression strength of the sandwich panels were improved significantly. The effect of diameter of polymer pins on indentation and compression behavior of both sandwich panels was studied and results showed that the diameter of polymer pins had a large influence on the compression and indentation behavior of through‐thickness polymer pin–reinforced FCS panel, and the effect of adding polymer pins to FCS panel on indentation behavior is similar to the effect of increasing the thickness of face sheet. The effect of strain rate on indentation behavior of FCS panel and through‐thickness polymer pin–reinforced FCS panel were studied, and results showed that both types of composite sandwich panels are strain rate dependent structure as by increasing strain rate, the indentation properties and energy absorption properties of these structures are increased. POLYM. COMPOS., 37:612–619, 2016. © 2014 Society of Plastics Engineers     

Adhesive joints between carbon fiber and aluminum foam reinforced by surface‐treated aramid fibers

Short aramid fibers have been successfully used to reinforce the interface adhesive property between carbon fiber/epoxy composites and aluminum foam, and to form aramid‐fiber “composite adhesive joints.” In this study, to further improve the reinforcing effect of the aramid‐fiber‐reinforced adhesive joints, aramid fibers were ultrasonic treated to conduct different surface conditions. Critical energy release rate of the carbon fiber/aluminum foam sandwich beams with as‐received and treated interfacial aramid fibers were measured to study the influence of the surface treatment on aramid fibers. It was found that reinforcements in critical energy release rate were achieved for all samples with treated aramid fiber as measured under double cantilever beam condition. The interfacial characteristics of the short aramid fibers with different surface condition were investigated and discussed based on scanning electron microscopy observations. It is suggested that advanced bonding between aramid fibers and epoxy resin was conducted after surface treatment, and more energy was therefore absorbed through fiber bridging during crack opening and extension process. POLYM. COMPOS., 36:192–197, 2015. © 2014 Society of Plastics Engineers     

泡沫夹芯结构板泡沫壁流道内的流动特性

沟槽型真空辅助树脂传递模塑成型工艺（VARTM）是一种新型的泡沫夹芯结构板成型方法,利用实验探明了泡沫夹芯结构板芯材上不可渗泡沫壁流道内的流动行为。实验结果表明,液体在泡沫壁流道的流动能力大幅降低,只有光滑壁流道的60%左右,泡沫壁流道的粗糙内表面是造成这种现象的主要原因。提出了相应的压力驱动流动方程,并采用等效渗透率来表征液体在泡沫壁流道内的流动能力,得到了考虑粗糙表面影响的等效渗透率计算公式,提出了一个正确计算不可渗泡沫壁流道内流动的处理方法。     

双向格构腹板增强泡沫夹层复合材料梁弯曲性能试验

复合材料夹层结构具有比强度高、比刚度高、可设计性强、耐腐蚀等特点,以聚氨酯泡沫为芯材,以玻璃纤维增强复合材料为面板和格构腹板,采用真空导入成型工艺,制备双向格构腹板增强泡沫夹层复合材料梁。对无格构泡沫夹芯复合材料梁,不同腹板高度、腹板间距双向格构增强泡沫夹层复合材料梁进行三点弯曲试验,研究其破坏模式和机理。基于泡沫填充矩形蜂窝芯材的等效十字模型,预估试件的抗弯刚度和挠度,计算值与试验值吻合较好。     

Skin‐core debonding in resin‐infused sandwich structures

Techniques for enhancing the interfacial fracture properties of foam‐based sandwich structures are investigated. Prior to manufacture, holes were drilled into a PET foam core in order to facilitate resin flow during the subsequent resin‐infusion process. Glass fibers were then inserted into the perforations in an attempt to increase the interfacial fracture toughness of the sandwich structure. The results from these tests are compared to data generated from similar tests on a plain PET core, as well as on samples in which no fiber reinforcement was incorporated into the vertical holes. The inclusion of fibers in the through‐thickness holes served to increase the skin‐core interfacial fracture toughness of the sandwich structures. Here, it was noted the highest values of fracture toughness were more than three times the value measured on the plain foam system. POLYM. COMPOS., 37:2974–2981, 2016. © 2015 Society of Plastics Engineers     

VARI成型不同处理方法泡沫夹芯复合材料工艺及性能研究

采取泡沫芯刻槽和泡沫芯导孔两种处理方法预制备泡沫芯材,采用VARI工艺成型泡沫夹芯复合材料,对复合材料进行无损检测,并对其成型效率、质量和力学性能进行研究。结果表明:刻槽和导孔处理可以有效地提高泡沫夹芯复合材料的成型效率,且其表面质量良好;三种泡沫夹芯复合材料泡沫与复合材料面板间均结合紧密,不存在贫胶、分层等缺陷;经刻槽处理后,泡沫夹芯复合材料的剥离强度有所下降,而弯曲强度和侧压强度略有上升;经导孔处理后,泡沫夹芯复合材料的剥离强度、弯曲强度和侧压强度均小幅下降。总的来看,不同处理工艺对VARI泡沫夹芯结构力学性能影响不大。     

Processing and property of carbon-fiber aluminum-foam sandwich with aramid-fiber composite adhesive joints

Thin tissues (or called webs) of short aramid fibers were added at the adhesive joints between carbon-fiber face sheets and aluminum-foam core to form aramid-fiber ‘composite adhesive joints’ for improving the interfacial bonding strength of sandwich structures and therefore other structural properties. In-plane critical compression loads and failure modes of carbon-fiber aluminum-foam sandwich beams with short aramid-fiber composite adhesive joints are investigated and discussed in this study. Improvements in critical compression loads were achieved for all specimens with aramid-fiber composite adhesive joints of different densities. It is suggested that the composite adhesive joints using low-density short aramid fibers is effective in promoting reinforcements against cracking and delamination at the interface between carbon-fiber face sheets and aluminum-foam core. The underlying interfacial strengthening and toughening mechanisms were discussed and analyzed based on observations from optical image and scanning electron microscopy.     

Foam sandwich composites with cyanate ester based syntactic foam as core and carbon‐cyanate ester as skin: Processing and properties

Foam sandwich composites were processed using cyanate ester‐based syntactic foam as core and carbon fabric‐cyanate ester composite as skin. They were processed by a one‐step compression‐molding technique. The mechanical performance of the sandwich composites was evaluated in terms of flatwise tensile strength (FTS), flatwise compressive strength, and edgewise compressive strength. The dependency of these properties on the core composition was investigated. FTS initially increased with the increase in resin content of the syntactic foam core. However, higher resin content in the core led to a diminution in FTS due to high void content. The flatwise compressive strength and edgewise compressive strength and the corresponding moduli values showed an increasing trend with increase in resin content of the core despite the presence of voids at high resin content. The failure modes of the composites under different loading conditions have been examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

玻璃纤维增强建筑用聚乙烯树脂复合材料的性能

采用剥离测试方法来表征制得的玻璃纤维增强建筑用聚乙烯树脂复合材料的界面黏结强度,并对其进行红外光谱、接触角、微观组织测试与分析。研究结果表明:采用浸润剂处理可以使玻璃表面生成新基团;浸润剂能够提高玻璃表面接触角,从而更易与树脂形成浸润状态,由此改善玻璃和树脂的界面结合状态,实现界面黏结特性的显著优化。在剥离测试中发现经浸润剂处理后,玻璃可以和树脂之间形成更强的界面结合作用;树脂从玻璃表面发生剥离之后,形成了光滑的玻璃片,同时还有部分纵横交错的划痕。     

Release Mechanisms for Pressure Sensitive Adhesive Tape on Silicone-Coated Glass

Regarding the function of the silicone release agent, the following two mechanisms, that is, the low energy surface of a cross-linked methyl hydrogen polysiloxane (MHPS) resin and the separation of a non-cross-linkable dimethyl polysiloxane (DMPS) oil itself have been compared. The 180° peel strength of the glass plate/silicone release agent/pressure sensitive adhesive (PSA) tape laminates decreased in the following order: un-coated > MHPS-coated > DMPS-coated glasses. ATR, ESCA and SEM observations of the PSA and glass surfaces after the peel test showed that no MHPS transferred from the glass surface to the PSA but a part of the DMPS transferred. From these results, it was concluded that, for decreasing peel strength, the separation of silicone oil (DMPS) itself is more effective than the low energy surface of the silicone resin (cross-linked MHPS).     

Moisture absorption in foam‐cored composite sandwich structures

The hygroscopic behavior of sandwich structures composed of E‐glass/polyester face sheets bonded to a PVC foam core exposed to 95% relative humidity and immersed in sea‐water is examined herein. Moisture uptake was monitored for 11 months yielding absorption curves for samples of polyester resin, laminated composites, PVC foam core, and a sandwich structure. The coefficients of diffusion and moisture saturation values extracted from the curves are significantly greater for the water immersed condition than for the exposed to elevated moisture one, and point to the foam core as the most absorbing material in the sandwich structure. The measured absorption curves are compared to a diffusion model which employs the calculated coefficient of diffusion, showing good agreement. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Analytical method for determination of temperature-induced interfacial shear stress in foam-core composite sandwich materials

Composite sandwich materials with glass fibre-reinforced plastic (GFRP) skins and a foam core have been widely used in civil engineering. However, the interfacial delamination is the main failure mode in practice, especially at elevated temperatures. Temperature-induced interfacial shear stress can be generated because of the different coefficients of thermal expansion of GFRP skin and foam core, which can weaken the interfacial bond strength of sandwich materials. In this study, to investigate the distribution of temperature-induced interfacial strain, an analytical model was developed by using the infinitesimal method. In the meantime, a series of foam-core composite sandwich materials were tested via a kind of non-direct test method at different temperatures to validate the accuracy of the proposed analytical model. Finally, the comparison between experimental and analytical results demonstrates that the proposed analytical model can predict the interfacial strain distribution of sandwich structures at elevated temperatures.     

High-velocity impact loading in honeycomb sandwich panels reinforced with polymer foam: a numerical approach study

The employment of lightweight structures is one of the most important goals in various industries. The lightweight sandwich panel is an excellent energy absorber and also a perfect way for decreasing the risk of impact. In this paper, a numerical study of high-velocity impact on honeycomb sandwich panels reinforced with polymer foam was performed. The results of numerical simulation are compared with the experimental findings. The numerical modeling of high-velocity penetration process was carried out using nonlinear explicit finite-element code, LS-DYNA. The aluminum honeycomb structure, unfilled honeycomb sandwich panel, and the sandwich panels filled with three types of polyurethane foam (foam 1: 56.94, foam 2: 108.65, and foam 3: 137.13 kg/m³) were investigated to demonstrate damage modes, ballistic limit velocity, absorbed energy, and specific energy absorption (SEA) capacity. The numerical ballistic limit velocity of sandwich panels, filled with three types of foam, was more than that of a bare honeycomb core and unfilled sandwich panel. In addition, the numerical results showed that the sandwich panel filled with the highest density foam could increase the strength of sandwich panel and the numerical specific energy absorption of this structure was 23% more than that of unfilled. Finally, the numerical results were in good agreement with experimental findings.

     

The Effect of Modification of an Epoxy Resin Adhesive with ATBN on Peel Strength

The effects of rubber content, rate of peel and temperature on peel strength of ATBN modified DGEBA based epoxy resin adhesives have been investigated. The fracture surfaces of peel test specimens and the distribution of rubber particles in cured bulk epoxy resin have been observed with SEM and TEM, respectively. The mechanical properties of bulk rubber modified epoxy resin have been also measured. The peel strengths increased with increasing rubber content, peel rate, and decreasing temperature. The peel strengths were superposed as a function of rate and temperature. Plots of the shift factors against temperature gave two straight lines, which followed an Arrhenius relationship. The region of temperature below the intersection of the two straight lines, temperature somewhat lower than T_g of epoxy adhesive, gave markedly high peel strengths and a stick-slip failure due to plastic deformation of the adhesive, and a number of micro holes produced by the rupture of rubber micro particles on the fracture surface. The region of temperature above the intersection gave lower peel strengths and an apparent interfacial failure with ductile fracture of the adhesive, and larger, shallow holes or no holes. From these results, the marked increase of peel strength was concluded to be mainly attributed to the plastic or viscoelastic deformation of epoxy matrix, the strong bond at the interface between rubber particles and epoxy matrix, and the dilation and rupture of a number of rubber particles.     

Behavior of sandwich structures and spaced plates subjected to high‐velocity impacts

This work evaluates the behavior of sandwich and spaced plates subjected to high‐velocity impacts. The sandwich structures were made of glass/polyester face‐sheet and a PVC foam core. The spaced plates were made of two plates of the same material of the sandwich face‐sheet at a distance equal to the core thickness. The residual velocity, the ballistic limit, and the damage area were selected to compare the response of both structures. The residual velocity and ballistic limit was very similar in both cases. Nevertheless, the damage area of sandwich structures and spaced plates differed due to the dissimilar properties between the sandwich core and the air inside of the spaced plates. An analytical model, based on energy criteria, was applied to estimate the residual velocity of the projectile, the absorbed energy by each face‐sheet, and the ballistic limit in the spaced plates. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Surface Modification of Epoxy Resin with Silicone-containing Block Copolymers

In order to improve oil and water repellency, silicone-containing block copolymers, composed of methylmethacrylate (MMA), glycidylmethacrylate (GMA), and polydimethylsiloxanemethacrylate (SMA), were blended in an epoxy resin. It was expected that the low surface energy dimethylsiloxane segments would adsorb and orient at the exterior of the resin to make a thin surface phase and the glycidyl groups would mesh with the epoxy resin by primary bonding. The techniques of X-ray photoelectron spectroscopy (ESCA), dynamic contact angle (DCA) and peel strength measurements of pressure sensitive adhesives were used to characterize the modified epoxy resin surface phases. The amount of Si_2p obtained via angular dependent ESCA investigation in the near surface region of the modified resin increased with decreasing sampling depth. With an increase in modifier content, both the amount of Si_2p and O_1s also increased. Both advancing and receding contact angles for an aluminum plate coated with modified resin, measured by dipping into and out of water, increased with the addition of these modifiers. The peel strength of a pressure sensitive adhesive tape affixed to the modified epoxy resin decreased dramatically with increasing modifier content. It was found that these copolymers were good surface modifiers to improve oil and water repellency and that they acted as release agents.     

复合材料泡沫夹层结构的缺陷评定方法研究

本文以厚壁碳纤维复合材料为面板,硬质聚氨酯泡沫为芯材制造复合材料泡沫夹层结构,模拟实际生产过程中容易出现的面板与芯材之间界面的脱粘和界面胶层过厚的现象,采用人工制造试块的方法,研究了超声波探伤对夹层复合材料缺陷的评定方法,解决了实际检测过程中的疑问,为夹层复合材料结构产品的质量检验提供依据。得出了粘接良好区胶层过厚不会被判定为脱粘的结论。     

Study of a 'T'-type peel test on a metal/polymer/metal sheet sandwich

This paper describes the specific 'T'-type peel mode in the case of a metal/polymer/metal sheet sandwich and gives experimental results on the influence of plastic deformation in the metallic substrates on the peel energy. We propose an experimental method of carefully determining the peel energy of a metal-polymer interface in a sandwich structure. Based on the mechanical properties of the stainless steel substrates and the maximum curvature of the metallic sheet measured experimentally during the peel test, several expressions for the clastoplastic deformation energy of the metal substrates are given. It is noteworthy that the curvature of the metal substrate layers depends not only on the mechanical properties of the material, but also on the work necessary to overcome the interfacial or cohesive forces. It is shown that even for thin metallic substrates (0.1 mm thick stainless steel), the work absorbed by the deformation represents roughly 50% of the total measured energy. During peeling the same specimen at different rates, the propagation peel force is higher or lower than the initiation force depending on the previous curvature of the metal sheets.     

Surface Modification of Epoxy Resin with Silicone-containing Block Copolymers

In order to improve oil and water repellency, silicone-containing block copolymers, composed of methylmethacrylate (MMA), glycidylmethacrylate (GMA), and polydimethylsiloxanemethacrylate (SMA), were blended in an epoxy resin. It was expected that the low surface energy dimethylsiloxane segments would adsorb and orient at the exterior of the resin to make a thin surface phase and the glycidyl groups would mesh with the epoxy resin by primary bonding. The techniques of X-ray photoelectron spectroscopy (ESCA), dynamic contact angle (DCA) and peel strength measurements of pressure sensitive adhesives were used to characterize the modified epoxy resin surface phases. The amount of Si_2p obtained via angular dependent ESCA investigation in the near surface region of the modified resin increased with decreasing sampling depth. With an increase in modifier content, both the amount of Si_2p and O_1s also increased. Both advancing and receding contact angles for an aluminum plate coated with modified resin, measured by dipping into and out of water, increased with the addition of these modifiers. The peel strength of a pressure sensitive adhesive tape affixed to the modified epoxy resin decreased dramatically with increasing modifier content. It was found that these copolymers were good surface modifiers to improve oil and water repellency and that they acted as release agents.