竹展平板拉伸剪切胶合性能

竹展平板是竹筒最大化利用的一种方式,以竹展平板为单元制备竹质人造板可减少胶黏剂使用量,还有利于加工,具有良好的应用前景。然而,竹材是一种天然梯度复合材料,纤维含量在竹壁径向呈现梯度变异,不同纤维含量的胶合面对竹展平板的胶合性能有重要影响。以无刻痕竹展平板为研究对象,参照拉伸剪切强度测试方法,探讨不同纤维含量的竹展平板胶合面在湿态和干态条件下的拉伸剪切强度和破坏方式;同时,分别研究热压压力和施胶量对不同组坯方式下竹展平板胶合性能的影响。结果表明:热压胶合的竹展平板胶合性能主要由基材性能决定,纤维含量较高的竹青?竹青组坯时的拉伸剪切强度高于其他两种组坯方式。基于不同纤维含量基材的干缩湿胀不一致,纤维含量较高的竹青面与纤维含量较低的竹黄面胶合时的湿态拉伸剪切强度保留率最低。竹黄?竹黄组坯时拉伸剪切强度随热压压力的增大而逐渐增加,而竹青?竹青和竹青?竹黄组坯时则先增大后减小。此外,竹黄?竹黄组坯时的干态剪切强度随施胶量的增大而增加。

The tensile shear bonding property of flattened bamboo sheet

Flattened bamboo sheet is made from bamboo culm in processes of softening,flattening,pressing,drying,etc.It is the method for maximum use of bamboo culm.At present,the flattened bamboo sheet is mainly used in chopping block.However,because of its large size,the flattened bamboo sheet has a good application prospect in glued laminated bamboo,which would be a large unit and can reduce the consumption of adhesive and facilitate the processing.Bamboo is a natural graded bio?composite,and the fiber content is gradient in bamboo culm wall in the ra?dial direction.The fiber content in different flattened bamboo sheet surface is a key factor affecting its bonding per?formance and properties.In this study,the flattened bamboo sheets were taken as the research objects.According to the tensile shear bonding strength test method,the tensile shear bonding strength and fracture modes of different fiber content bonding surfaces in dry and wet condition were discussed.Moreover,the effects of hot?pressing pressure and resin content on the different fiber content surface bonding strengths were also studied.The results indicated that the tensile shear bonding strengths of flattened bamboo sheets were determined by the properties of flattened bamboo sheets.For different assemble patterns,the tensile shear bonding strengths in both dry and wet condition were as outer?outer>outer?inner>inner?inner.When it was in wet condition,the tensile shear strength in three assemble patterns all decreased largely.Based on the different drying shrinkages and wet expansions of the substrates with different fiber contents,the uniform fiber content and properties of the flattened bamboo sheets were beneficial to the wet tensile shear bonding strength.Retention rate of inner?inner assemble pattern with low fiber content was 46.12%,which was the largest.In this study,the high hot?pressing pressure made the two bonding surfaces closer,which increased the tensile shear bonding strength.The tensile shear bonding strength of inner?inner assemble pattern increased,which was due to the close fitting of bonding surface.However,the tensile shear bonding strength of the other two assemble pat?terns increased firstly and then decreased because of the adhesive extrusion in dense fiber bonding surface.Likewise,the dry tensile shear bonding strength of inner?inner assemble pattern increased with the increase of resin content,while the dry tensile shear bonding strength of the other two assemble patterns increased firstly and then decreased.Therefore,the fiber content in different flattened bamboo sheets not only influenced its properties but also greatly af?fected the adhesive permeation and bonding strength.