服装行业网络营销的国外发展

1、服装行业，在世界的前景怎么样？

——原标题：2018年全球服装零售行业市场现状与发展趋势分析 零售额稳步增长

全球服装零售规模稳步扩大

受全球经济增长的推动，人们可支配收入稳步提升，进而推动全球服装零售业规模不断壮大。根据Frost&Sullivan数据统计，2018年，全球服装零售业总零售额达14382亿美元，2014-2018年间复合年增长率为4.2%。

分类别来看，全球服装可分为下装、衬衫、运动休闲服、内衣、毛衣、外套、定制及其他。2018年，全球服装零售市场主要以下装及衬衫为主，零售额均超过2300亿美元，占服装零售总零售额比重分别为16.3%、16.0%。

从增速角度比较，2014-2018年期间，运动休闲服零售额增长更为明显，其复合年增长率达5.6%，主要得益于全球健康及健身潮流日益盛行以及着装规范的普遍放松，未来运动休闲服仍有巨大增长潜力。

分定位来看，全球服装大致可分为奢侈、高端(桥接、优良)、中端、大众。目前，全球服装零售市场还是以中端及大众品牌为主，2018年零售额分别达4674亿美元、4143亿美元，占比分别为32.5%、28.8%。

增速方面，高端市场增长显著，在2014-2018年间，尽管市场份额不大，但桥接及优良市场品牌的复合年增长率分别达4.5%、4.9%，这得益于新兴品牌的风靡。新兴品牌较迎合大众消费市场的品牌，有着更高的溢价。

分品牌来看，传统品牌占据了全球服装零售市场约87.6%的份额，而网络原生品牌及平台约占12.4%。2014-2018年，传统品牌的全球服装零售额从10755亿美元增至12599亿美元，复合年增长率为4.0%;而同期网络原生品牌零售额从1444亿美元增至1783亿美元，复合年增长率达5.4%，高出传统品牌1.4个百分点。

全球服装零售呈现五大趋势

未来，全球服装零售行业将呈现以下趋势：一是全球消费者对时尚商品的需求将进一步升级为有趣、随时可用、可持续且价格合理，因此越来越多的消费者正转向服装租赁和二手服装，随着二手、租赁等业务模式的不断发展，品牌独家销售或许不再成为消费者的购物路径。

二是年轻的一代，包括Z世代和千禧一代将成为服装零售的购买主力军。这一购物主力军越来越多的依赖自己的购物习惯，并且看重商品、品牌与自己的价值观是否苟同。

三是快速已经逐渐成为了行业标准，尤其是对在线零售而言更是如此。除了像电商巨头亚马逊推出了快速发货、配送等一站式服务外，越来越多的平台正在试图加快购物流程，如将购物功能在社交媒体端口进行整合以及视觉识别购物等。从技术到服务，及时快速的购物体验正在成为全新的消费指标。

四是颠覆将成全球服装零售行业的关键词之一。外部来看，社媒势头和技术发展催生了大批新兴品牌和商业模式，而这些角色正在挑战传统行业现状。与此同时，为了在需求旺盛的年轻消费者中竞争并保持相关性，越来越多的传统品牌正在进行自我颠覆以呼应新趋势，试图打造自己的全新品牌、产品和商业模式。

五是服装款式设计和潮流更替不再是一个漫长的过程，品牌和商家们将利用技术加快产品线更迭的频率。例如，自动化数据工具将有助于企业采用灵活的订单生产周期，更快地响应市场趋势和消费者需求。

——以上数据来源请参考于前瞻产业研究院发布的《中国服装零售行业市场前瞻与投资战略规划分析报告》。

2、当前网络营销国内外研究水平

网站优化已经成为网络营销经营策略的必然要求。如果在网站建设中没有体现网站优化和搜索引擎优化的基本思想，在网络营销水平普遍提高的网络营销环境中是很难获得竞争优势的。新竞争力提供最专业的网站优化分析建议与网站优化解决方案。新竞争力的网站优化思想：通过对网站功能、网站结构、网页布局、网站内容等要素的合理设计，使得网站更好的向用户传递网络营销信息，发挥最大的网络营销价值。网站优化是一项系统性和全局性的工作，包括对用户的优化、对搜索引擎优化、对运营维护的优化。
新竞争力对网站优化思想及网站优化方法有深入的研究，发表了大量广为传播的网站优化研究文章和针对多个行业的网站优化状况研究报告，无论对新网站的优化策略还是运营中网站的优化升级均有独到的认识和丰富的实践经验。新竞争力网络营销管理顾问为国内外众多网站提供了针对性的网站优化解决方案并取得了显著效果（其中包括多家知名B2B电子商务网站、B2C网站、行业门户网站、WEB2.0网站和各类企业网站）。

新竞争力的网络营销专家团队是网站优化思想的缔造者（在冯英健专著《网络营销基础与实践》第二版有详细描述），同时新竞争力也是中国互联网协会网站建设指导规范的发起单位，承担中国互联网协会网站建设指导规范的制定工作。新竞争力的网站优化方案遵照国际WEB标准和中国中国互联网协会网站建设指导规范制定，居于国际领先地位。新竞争力网站优化解决方案是从网站运营策略层面对网站进行的整体优化，是关系到网站运营成效的全局性的工作，是其他片面的搜索引擎优化和SEO排名所无法相提并论的。系统的网站优化可以达到最好的、持久的搜索引擎优化效果，并且可以为用户提供最有价值的信息和服务，而单纯的搜索引擎排名仅仅是为了搜索引擎检索，其效果是局部的、短暂的，也可能是后患无穷的。

新竞争力网络营销管理顾问（www.jingzhengli.cn）建议，如果您正在或者将要建设一个新的网站，最理想的情况是在网站策划阶段就将网站优化的基本思想融入到网站建设方案中，并在网站建设过程中贯彻实施。这样可以让新发布的网站直接从高起点开始运营，可以大大提高网站运营的效果，也节省了网站优化改造的费用。 如果您的网站在运营推广中遇到网站访问量增长的瓶颈等方面的问题，新竞争力建议您尽可能早的实施网站优化策略，以免造成无法弥补的损失。如果不能比竞争者早一步，至少也不应该落后太多。

3、国外网络营销发展现状

多数国家已进入信息时代，网络接入和先进的终端设备给互联网营销提供了一个良好的发展环境。下面举几个例子来解释下国外网络营销的现状：

美国也在不断地完善互联网营销的法律法规体系来给消费者创造一个良好的网络购物环境。

新加坡不仅及时制定相关政策法规，引导企业进行信息化基础设施建设，还积极推动网络营销的发展，消除电子商务发展的安全障碍，并确保网上交易者获得全面、安全和高质量的服务。

以电子产品著称的日本也正在积极实施互联网营销， 而这对于加大电子产品在全球的市场占有份额，促进企业转型，助推经济增长起到了关键性的作用。

由于互联网营销因不受空间、地域、时间限制的优势， 也逐渐成为重要的市场交易模式，网络营销已成为经济最具有活力的增长点。

4、我国和国外的服装行业发展现状？

由于市场的开放，出口纺织品数量的增加，现行标准已不能满足产品质量和市场变化的要求。大多数的合资企业、独资企业以及有出口任务的企业，采用协议标准，按供需双方的协议合同考核和验收产品。而习惯于依赖国家标准或行业标准的企业，声称没有标准制约了企业的产品开发。

纵观国内纺织品市场尤其是制成品和服装市场上涌现出的很多被消费者认可的名牌产 品，其生产企业无一不是执行严格的技术标准和检验制度，无一不是采用优于国家标准和行业标准的企业内控标准。名牌产品是以优良的产品质量为基础，以高水准的标准为支撑，这些共识和实践对促进纺织工业的技术进步和产品质量的提高起到了积极的作用。

我国的纺织品标准现状

与纺织工业的发展相适应，我国纺织标准化工作不断地得到完善和提高，取得不小的成绩，纺织标准化工作为适应国家的经济建设和纺织工业的发展需要做出了应有的贡献。表现在：

1、从纺织材料到制成品和服装的标准已形成体系和规模。截止2002 年底，共有纺织品和服装标准885 个(不包括纤维原料标准)，其中国家标准383个，纺织行业标准502个，形成了以产品标准为主体，以基础标准相配套的纺织标准体系，包括术语符号标准、试验方法标准、物质标准和产品标准四类，涉及纤维、纱线、长丝、织物、纺织制品和服装等内容，从数量和覆盖面上基本满足了纺织品和服装的生产和贸易需要。

2、纺织品标准的采标率列为前位，基础标准与国际接轨。根据国家有关部门的统计，对国际标准的采标率，国内平均水平约为44％，而纺织品的采标率达80％。ISO中有关纺织品和服装的标准约有280多个。纺织行业对这些国际标准进行了研究，已经在不同程度上采用或已列入年度采用计划。除采用国际标准外，还不同程度的采用了国外先进国家的标准，如美国标准、英国标准、德国标准和日本标准等。特别是基础的、通用的术语标准和方法标准基本上采用了国际标准和国外先进标准，使制定的国家标准达到了国际标准或相当于国际标准的水平。

3、各类标准发挥了巨大作用。与国际接轨的基础标准，对统一纺织工业科技术语、统一纺织材料和产品的检测手段、统一规范产品的性能指标起到了重要的作用。特别是依据这些检测方法试验出具的数据不仅在全国范围内具有可比性，而且也得到了国外客户的认可，对纺织品贸易起到了不可低估的作用。制定的大量的纺织产品标准，适应了产品的发展和需要，解决了无标生产的问题，为企业的大量产品进入市场提供了技术依据。

4、企业的标准化理念对提高产品质量起到了关键作用。从1989年《标准化法》实施以来，企业的标准化工作逐步加强，参与标准化的热情越来越高涨。

但是，随着近年来市场经济的发展，现有的标准体制和标准内容逐渐显现出了其弊端，具体表现在：

1、在原有计划经济体制下，我国的纺织产品标准是生产型的，标准的制定以指导生产为主要出发点，技术要求与生产工艺紧密相联，指标定的过细过死，特别是标准的制修订速度滞后于产品的开发速度。有些企业认为标准水平太低，而有的企业却认为标准指标过高，形成了对标准的不同要求和评价。

2、随着纺织制品的成品化成为趋势，消费者对服饰和家庭装饰水平要求的提高，原料质量与制成品质量不配套的问题日益突出。例如，面料标准的色牢度差，水洗尺寸变化率大，缺乏实用性能考核指标等，由于标准不衔接引起的纠纷时有发生，消费者的投诉难以得到解决。

3、以前采标的指导思想是结合中国国情，考虑到国内现有设备和工艺条件，因此使我国采标的多数标准为“ 非等效”或“参照”。除基础标准接轨程度较高外，尽管有不少的产品标准前言中写明是采用国际或国外先进标准，但仅有少数指标甚至个别指标与国外标准一致，或采用的试验方法是采用国际标准的，因此，大多数产品标准的指标和水平没有真正与国外接轨。

4、由于市场的开放，出口纺织品数量的增加，现行标准已不能满足产品质量和市场变化的要求。大多数的合资企业、独资企业以及有出口任务的企业，采用协议标准，按供需双方的协议合同考核和验收产品。而习惯于依赖国家标准或行业标准的企业，声称没有标准制约了企业的产品开发。

与国外先进标准的差距

首先，形成的标准体系不同。ISO或国外的国家层面上的纺织标准，主要内容是基础类标准，重在统一术语，统一试验方法，统一评定手段，使各方提供的数据具有可比性和通用性。形成的是以基础标准为主体，再加上以最终用途产品配套的相关产品标准的标准体系。在产品标准中仅规定产品的性能指标和引用的试验方法标准。对大量的产品而言，国外是没有国家标准的，主要由企业根据产品的用途或购货方给予的价格，与购货方在合同或协议中规定产品的规格、性能指标、检验规则、包装等内容。

我国现行的纺织产品标准有不少是计划经济体制时的产物，形成的标准体系以原料或工艺划分的产品标准为主，目前主要分为棉纺织印染、毛纺织品、麻纺织品、丝产品、针织品、线带、化纤、色织布。近年来也以用途制定标准，但所占比例极小。标准中除性能指标外，还包括出厂检验、型式检验、复验等检验规则的内容，形成了各类原料产品“纱 线―――本色布―――印染布”的标准链。

其次，标准发挥的职能不同。国外将国家层面上的公开标准作为交货、验收的技术依据，从指导用户购买产品的角度和需要来制定，人们称之为贸易型标准。企业标准才是作为组织生产的技术依据。这种贸易型标准的技术内容规定的比较简明，比较笼统，比较灵活。

与之相反，我国大多数的产品标准的职能是用以组织生产的依据，从指导企业生产的角度的需要来确定，人们称之为生产型标准。为了便于企业生产，标准在技术内容方面，一般都规定的比较具体，比较详细，比较死。

随着市场经济的发展，纺织产品的新品种不断涌现，决定了简明灵活的贸易型标准更能符合市场的需要。我国的生产型标准范围较窄，覆盖的产品种类较少，造成标准的数量不少，但仍跟不上产品的发展速度。

第三，标准水平有差距。由于标准的职能不同，标准技术内容，如在考核项目的设置上，在性能指标的水平上等均有一定的差距。

国外根据最终用途制定的面料标准，考核项目更接近于服用实际，如耐磨、纱线滑移阻力、起毛起球、耐光色牢度等。我国的面料标准还缺少诸如接缝滑移、起毛起球、干洗尺寸变化、耐光色牢度等考核指标，不能适应人们对服用产品舒适美观性的要求。对服装的考核主要侧重服装的规格偏差、色差、缝制、疵点等外观质量，判定产品等级时忽略了 构成服装的主要元素―――面料和里料。

我国按生产型标准理念制定的标准，不能适用贸易关系超出生产方和购货方这种情况，例如，按染料类别和工艺制定不同的色牢度等级，在贸易交货验收中确定考核依据较为困难。而国外标准的质量指标控制严格，色牢度普遍高于国内指标1～1.5级，尤其是摩擦色牢度相差更多。

翻开产品标准，为数不少的标准文本中写有“优等品相当于国际先进水平，一等品相当于国际一般水平”等，实际上仅是个别单项指标水平达到国际水平，但综合性能达不到；还有个别标为采标的标准，其内容与国外标准相差甚远。

第四，国外标准形成了技术壁垒。随着贸易壁垒逐渐减小，各国都在借助于TBT有关条款规定，制造技术壁垒。而制造技术壁垒的有效途径就是法规和标准。欧洲议会和欧盟委员会2002年7月19日共同颁布的指令2002 ／61／EC―《对欧盟委员会关于限制某些危险物质和制剂(偶氮染料)的销售和使用的指令76／769／EEC的第 19次修改令》，连同欧盟委员会2002年5月15日颁布的关于修改并发布授权纺织产品使用欧共体生态标签(Ec o-label)的决定(2002／371／EC)，欧盟在为纺织品和日用消费品的市场准入构筑完整的“绿色屏障” 方面迈出了两个重大的步伐。中国作为全球最大的纺织品生产和出口国，可能受到的影响显然是不可低估的。

由于诸多原因，在进口纺织品中不乏有劣质产品和不合格产品。但我国技术法规和强制性标准欠缺，不能有效监督进口产品的质量。2000 年就着手制定的《纺织品基本安全技术要求》至今还未批准，对国外的不良产品起不到抵挡作用。

5、谁知道国外网络营销发展现状？

国外的网络广告模式发展状况。
网络广告是指利用国际互联网这种载体，通过图文或多媒体方式，发布的赢利性商业广告，是在网络上发布的有偿信息传播。
美国作为网络广告的发源地，其网络广告在广告市场仍占较少部分，但网络广告市场规模增长速度不容小视；日本网络广告具有受到其传统市场营销方式的影响大的特征，网络广告与电视广告以及电台广告的呈现融合趋势；韩国的网络广告市场规模基本保持着稳步增长的趋势；在欧洲，英国网络广告发展速度最快，欧洲网络广告市场的广告主主要为IT类和通信类企业。
07年的今天，国内外谈论的不再是简简单单的网络广告了，网络广告经过7年的发展，大家的追求不再是做不做网络广告的选择，而是如何选择更好的网络广告模式了。来电付费广告模式是现在大家所津津乐道的，来电付费是在网络广告的基础上增加了客户与企业主的电脑语音沟通的过程，而它的费用是按照电话的时长而定的。美国AOL、Findwhat.com, Google等老牌互联网巨头，纷纷试水通话付费广告业务，受到中小企业，尤其是从事批发、贸易等广告主的青睐，行业发展势头强劲。而在中国尚处于萌芽期，希望向万维联讯等技术提供商能让来电付费的推广工作做到最好。希望百度、雅虎和google等网站能再次谱写网络新的历史篇章。

6、服装网络营销国内外研究现状怎么写

?

7、中小型企业网络营销 国内外研究现状

现在中小企业的网络营销现状跟在线下开个实体店，店里装修很一般，版也没有做点引导客户的措施，权导致虽然进来看的人很多，但销量很差，最后不得不放弃，是差不多的。现在几乎所有的企业都是在做百度竞价、SEO、外推等技术，确实带来了大量的人气，但成交率太低，或者说入不敷出也不为过。
总结：中小企业做网络营销不是做个网站，然后开始推广就行了的，如果这样，只会白白浪费大量的人力、物力、财力。网络营销是一个长期的过程、是一个积累的过程，在实际操作的过程中难免会遇到各种各样的问题，要做的就是分析数据掌握对的方法，坚持下去。

8、高分求[国际服装发展现状和品牌服装营销]方面的外文文献

这是一片写的不错的

Effect of fiber architecture on flexural characteristics and fracture of fiber-reinforc

Vistasp M. Karbharia, Corresponding Author Contact Information, E-mail The Corresponding Author and Howard Strasslerb
aMaterials Science & Engineering Program, and Department of Structural Engineering, MC-0085, University of California San Diego, Room 105, Building 409, University Center, La Jolla, CA 92093-0085, USA.
bDepartment of Restorative Dentistry, Dental School, University of Maryland, Baltimore, MD, USA
Received 10 December 2005; revised 25 June 2006; accepted 31 August 2006. Available online 7 November 2006.

Abstract

Objective

The aim of this study was to compare and elucidate the differences in damage mechanisms and response of fiber-reinforced dental resin composites based on three different brandsnext term under flexural loading. The types of reinforcement consisted of a unidirectional E-glass prepreg (Splint-It from Jeneric/Petron Inc.), an ultrahigh molecular weight polyethylene fiber based biaxial braid (Connect, Kerr) and an ultrahigh molecular weight polyethylene fiber based leno-weave (Ribbond).

Methods

Three different commercially available fiber reinforcing systems were used to fabricate rectangular bars, with the fiber reinforcement close to the tensile face, which were tested in flexure with an emphasis on studying damage mechanisms and response. Eight specimens (n = 8) of each type were tested. Overall energy capacity as well as flexural strength and molus were determined and results compared in light of the different abilities of the architectures used.

Results

Under flexural loading unreinforced and unidirectional prepreg reinforced dental composites failed in a brittle previous termfashion,next term whereas the braid and leno-weave reinforced materials underwent significant deformation without rupture. The braid reinforced specimens showed the highest peak load. The addition of the unidirectional to the matrix resulted in an average strain of 0.06 mm/mm which is 50% greater than the capacity of the unreinforced matrix, whereas the addition of the braid and leno-weave resulted in increases of 119 and 126%, respectively, emphasizing the higher capacity of both the UHM polyethylene fibers and the architectures to hold together without rupture under flexural loading. The addition of the fiber reinforcement substantially increases the level of strain energy in the specimens with the maximum being attained in the braid reinforced specimens with a 433% increase in energy absorption capability above the unreinforced case. The minimum scatter and highest consistency in response is seen in the leno-weave reinforced specimens e to the details of the architecture which restrict fabric shearing and movement ring placement.

Significance

It is crucial that the appropriate selection of fiber architectures be made not just from a perspective of highest strength, but overall damage tolerance and energy absorption. Differences in weaves and architectures can result in substantially different performance and appropriate selection can mitigate premature and catastrophic failure. The study provides details of materials level response characteristics which are useful in selection of the fiber reinforcement based on specifics of application.

Keywords: Fiber reinforcement; Dental composite; Flexure; Damage tolerance; Architecture; Unidirectional; Braid; Leno-weave

Article Outline

1. Introction
2. Materials and methods
3. Results
4. Discussion
5. Summary
References

1. Introction

A range of fillers in particulate form have conventionally been used to improve performance characteristics, such as strength, toughness and wear resistance, Although the addition of fillers and recent changes in composition of resin composites have been noted to provide enhanced wear resistance [1] and [2], conventional filler based systems are still brittle as compared to metals. Sakaguchi et al. [3] reported that these were prone to early fracture with crack propagation rates in excess of those seen in porcelain. This is of concern since clinical observations have demonstrated that under forces generated ring mastication the inner faces of restorations can be subject to high tensile stresses which cause premature fracture initiation and failure [4]. In recent years, fiber reinforcements in the form of ribbons have been introced to address these deficiencies [5]. By etching and bonding to tooth structure with composite resins embedded with woven fibers adapted to the contours of teeth periodontal splints, endodontic posts, anterior and posterior fixed partial dentures, orthodontic retainers and reinforcement of single tooth restorations can be accomplished. While the science of fiber-reinforced polymer composites is well established, the application of these materials in dental applications is still new and aspects related to material characterization, cure kinetics and even placement of reinforcement are still not widely understood.

Due to the nature of filled polymer and ceramic systems that have been used conventionally, most material level tests designed and used extensively, for the characterization of dental materials, emphasize the brittle nature of materials response. In many cases the tests and the interpretation of results, are not suited to the class of fiber-reinforced polymeric composites, wherein aspects, such as fiber orientation, placement of fabric and even scale effects are extremely important. The difference in characteristics and the need to develop a fundamental understanding of response of continuous fiber and fabric, reinforced dental composites has recently been emphasized both through laboratory and clinical studies. Recent studies have addressed critical aspects, such as effects of fabric layer thickness ratios and configurations [6], fiber position and orientation [7] and even test specimen size [8]. However, the selection and use of continuous reinforcement is largely on an ad hoc basis, with diverse claims being made by manufacturers, without a thorough understanding of the materials based performance demands for the material by the specifics of an application (for example, the fabric architecture required for optimized performance of a post are very different from those for a bridge) or details of response characteristics at levels beyond those of mere “strength” and “molus”. Further, each fabric is known to respond in different manner to manipulation and drape (i.e. conformance) to changes in substrate configuration [9]. The architecture of the fabrics permits movement of fibers or constraint thereof and even shearing of the structure, to different extents. Weave patterns have also been noted to be important in the selection of composite materials for dental applications based on the specifics of application [10]. Thus, clinically, when each of the different fabric configurations is used to reinforce dental composites, there are manipulation changes that occur to some of the fabric materials. For the biaxially braided material, the fiber orientation can change after cutting and embedment in the composite when adapting to tooth contours. The fibers in the ribbon spread out and separate from each other and become more oriented in a direction transverse to the longitudinal axis of the ribbon. When the leno-weave is cut and embedded in dental composites, the fiber yarns maintain their orientation and do not separate from each other when closely adapted to the contours of teeth. However, e to the orthogonal structure gaps can appear within the architecture providing local areas unreinforced with fiber reinforcement. The unidirectional glass fiber material does not closely adapt to the contours of teeth e to the rigidity of the fibers. It is difficult to manipulate the fibrous material which leaves the final composite material thicker; further manipulation causes glass fiber separation with some visible fractures of the fibers themselves.

The aim of this study is to experimentally assess the flexural response of three commercial fiber/fabric reinforcement systems available for dental use and to compare performance based on different characteristics and to elucidate differences based on details of fabric architecture and fiber type.

2. Materials and methods

Three different fabric-reinforcing procts, all in ribbon form, were used in this investigation. The first is a 3 mm wide unidirectional E-glass prepreg structure with no transverse reinforcement (Splint-It, Jeneric/Petron Inc.1) designated as set A, whereas the other two are formed of ultra-high molecular weight polyethylene fibers in the form of a 4 mm wide biaxial braid (Connect, Kerr), designated as set B and a 3 mm wide Leno-weave (Ribbond, WA), designated as set C. The first is a pure unidirectional which intrinsically gives the highest efficiency of reinforcement in the longitudinal direction with resin dominated response in the transverse direction. The second is a biaxial braid without axial fibers, which provides very good conformability and structure through the two sets of yarns forming a symmetrical array with the yarns oriented at a fixed angle from the braid axis. The third architecture has warp yarns crossed pair wise in a figure of eight pattern as filling yarns providing an open weave effect for controlled yarn slippage and good stability.

Multiple specimens of the fabrics were carefully measured and weighed and the average basis weight of the biaxial braid was determined to be 1.03 × 10−4 g/mm2 whereas that for the leno-weave was 1.42 × 10−4 g/mm2. It was noted that the unidirectional had an aerial weight of 2.2 times that of the other two. Rectangular test bars of size 2 mm × 2 mm × 48 mm were constructed from layered placement of a flowable composite resin (Virtuoso FloRestore, Demat) in polysiloxane molds, with glass slides held on top with rubber bands and light cured for 60 s using a Kulzer UniXS laboratory polymerization lamp. In the case of sets B and C the fabric was first wetted and then placed on the first layer of the flowable composite resin such that the fiber reinforcement was placed between 0.25 and 0.5 mm from the bottom surface (which would be used as the tensile surface in flexural testing). The addition of higher molus material at or near the tensile surface is known from elementary mechanics of materials to increase flexural performance and has been verified for dental composite materials by Ellakwa et al. [11] and [12]. Care was taken to maintain alignment of the fibers and fabric structure and not cause wrinkling or lateral movement which would affect overall performance characteristics. The fabric reinforced specimens had only a single layer of reinforcement near the bottom surface with the rest of the specimen having no fiber reinforcement. This general configuration for flexural specimens has been used previously by Kanie et al. [13]. In the current investigation, fiber weight fraction in the single layer was between 37 and 42% but is significantly lower if determined on the basis of the full thickness of the overall specimen. Unreinforced bars of the resin were also fabricated the same way for comparison and were designated as set D.

Eight specimens (n = 8) from each set were tested in three-point flexure using a span of 16 mm which provides a span to depth (l/d) ratio of 16, which is recommended by ASTM D 790-03 [14]. It is noted that flexural characteristics can be substantially affected by choice of the l/d ratio which intrinsically sets the balance between shear and bending moment, with shear dominating on shorter spans. Load was introced through a rounded crosshead indenter placed in two positions—parallel to the test specimen span (P1) and perpendicular to the test specimen span (P2). The load head indenter was of 4 mm total length. This was done to assess effects of load introction since ribbon architecture had fibers at different orientations. Tests were concted at a displacement rate of 1 mm/min and a minimum of eight tests were concted for each set. Loading was continued till either the specimen showed catastrophic rupture or the specimen attained a negative slope of load versus displacement with the load drop continuing slowly past peak to below 85% of the peak load. This level was chosen to exceed the 0.05 mm/mm strain limitation of apparent failure recommended by ASTM D790-03 [14] so as to enable an assessment of ctility of the specimens. Specimens were carefully examined for cracking, crazing and other damage.

The flexure strength was determined as

Click to view the MathML source (1)

where P is the applied load (or peak load if rupture did not occur), L the span length between supports and b and d are the width and thickness of the specimens, respectively.

While the tangent molus of elasticity is often used to determine the molus of specimens, by drawing a tangent to the steepest initial straight-line portion of the load-deflection curve to measure the slope, m, which is then used as

Click to view the MathML source (2)

in the current case a majority of the specimens show significant changes in slopes very early in the response curve indicating microcracking and non-linearity. Since these occur fairly early the molus determined from the initial tangent has significant statistical variation. In order to determine a more consistent measure of molus the secant molus of elasticity as defined in ASTM D790-03 [14] is used herein, with the secant being drawn between the origin and the point of maximum load to determine the slope m, which is then used in Eq. (2). This also has the advantage of providing a characteristic that incorporates the deformation capability, thereby differentiating between specimens that reach a maximum load at low deformation (such as, the unreinforced composite and the unidirectional reinforced composite) and those that show significant deformation prior to attainment of peak load (such as, the specimens reinforced with the braid and leno-weave).

The matrix material is generically more brittle than the fiber and usually has a lower ultimate strain. Thus, as the specimen bends the matrix is likely to develop a series of cracks with the initiation and propagation of cracks depending not just on the type and positioning of the reinforcement, but also on the strain capacity of the neat resin areas. It is thus of use to compute the strain in the composite under flexural load and this can be determined as

Click to view the MathML source (3)

where D is the midspan displacement.

The toughness of a material can be related to both its ctility and its ultimate strength. This is an important performance characteristic and is often represented in terms of strain energy, U, which represents the work done to cause a deformation. This is essentially the area under the load-deformation curve and can be calculated as

Click to view the MathML source (4)

where P is the applied load and x is the deformation. In the case of the present investigation, two levels of strain energy are calculated to enable an assessment of the two response types. In the first, strain energy is computed to the deformation level corresponding to peak load (which is also the fracture load for sets A and D). In the case of specimens that show significant inelastic deformation (sets B and C) strain energy is also computed till a point corresponding to a deformation of 11.5 mm at which point the load shows a 15% drop from the peak. Post-peak response in flexural has earlier been reported by Alander et al. [8].

3. Results

The application of flexural loading was seen to result in two different macroscopic forms of response. In the case of specimens from sets A and D (reinforced with a unidirectional fabric and unreinforced) failure was catastrophic, in brittle fashion, at peak load, whereas in the case of specimens from sets B and C the attainment of peak load was followed by a very slow decrease in load with increasing displacement, representative of inelastic or plastic, deformation. Typical response curves are shown in Fig. 1 as an example.

Display Full Size version of this image (24K)

Fig. 1. Typical flexural response.

The variation in flexural strength (plotted here in terms of stress at peak load) with type of specimen and load introction method is shown in Fig. 2. The highest strength was achieved by specimens with the braided fabric wherein on average a 125% increase over the unreinforced specimens was attained. Statistical analysis with ANOVA and Tukey's post hoc test revealed that method of load introction did not affect the results and that further there were no significant differences in overall peak strength results between sets A and B (specimens containing the unidirectional and braided fabrics). Significant differences (p < 0.003) were noted between sets B and C. It is, however, noted that in sets B and C, failure did not occur at the peak load, with load slowly decreasing with increase in midpoint deflection. A comparison of flexural stresses for these systems at peak load and load corresponding to a deflection of 11.5 mm is shown in Fig. 3. As can be seen the two systems show significant inelastic deformation with drops of only 12.8, 12.1, 11.7 and 9.5% from the peak, emphasizing the stable, ctile and non-catastrophic, post-peak response in these systems.

Display Full Size version of this image (28K)

Fig. 2. Flexural strength at peak load.

Display Full Size version of this image (50K)

Fig. 3. Comparison of flexural stresses in specimens having non-catastrophic failure modes.

A comparison of secant molus (measured to the peak load) for the different sets is shown in Fig. 4. As can be seen, with the exception of the unidirectional system, the apparent moli were lower than that of the unreinforced specimens. It is also noted that although the Tukey post hoc tests do not show a significant difference e to orientation of load indenter, the level for the unidirectionals is only 0.1022 compared to 1 for the others. Removal of a single outlier from P1 results in p < 0.007 indicating a strong effect of orientation of the indenter with the secant molus being 17.7% lower with the indenter placed parallel to the fibers, which results in splitting between fibers and uneven fracture with less pullout.

Display Full Size version of this image (25K)

Fig. 4. Comparison of secant moli under flexural loading.

As was noted previously, both the unreinforced samples (set D) and the unidirectional prepreg reinforced specimens (set A) failed in catastrophic fashion at deformation levels significantly less than those at which the other two sets reached the inelastic peak. Since sets B and C did not fracture but showed large deformation with some partial depth cracking through the matrix it is important to be able to compare the levels of strain attained on the tension face using Eq. (3). This comparison is shown in Fig. 5 at the level of peak load (which is the fracture/failure load for sets A and D). While the addition of the unidirectional to the matrix resulted in an average strain of 0.06 mm/mm which is 50% greater than the capacity of the unreinforced matrix, the addition of the braid and leno-weave resulted in increases of 119 and 126%, respectively, emphasizing the higher capacity of both the UHMW polyethylene fibers and the architectures to hold together without rupture under flexural loading. It should be noted, as a reference, that the strain at the point at which the tests on sets B and C were stopped, at a midpoint deflection of 11.5 mm, was 0.135 mm/mm, which represents a 233% increase over the level attained by the unreinforced matrix. The us