CAJ | 학술논문

为了定量表征不同壳层材料对芯壳结构竹塑复合材料冲击断口复杂程度的影响，以造纸剩余物竹屑和高密度聚乙烯（high density polyethylene，HDPE）作为芯层材料，以纯HDPE、竹浆纤维/HDPE、纳米碳酸钙/HDPE和白泥/HDPE分别作为壳层材料，采用熔融共挤工艺制备芯壳结构竹塑复合材料。在室温（23℃）环境下，测试了复合材料无缺口冲击强度，采用扫描电镜对4种不同壳层材料断口进行形貌分析，基于分形理论和图像处理技术，运用像素点法计算了复合材料的冲击断口表面分形维数，考察了复合材料断口表面分形维数和冲击强度的关系。结果表明，不同壳层材料的芯壳结构竹塑复合材料冲击断口表面分形维数存在一定差异，壳层为HDPE的复合材料断口表面分形维数最大，为2.2204，壳层为白泥/ HDPE的分形维数最小，为2.2075。不同壳层复合材料冲击断口表面分形维数拟合曲线的决定系数均大于0.98，说明复合材料断口表面分形特征显著。并且，复合材料断口表面分形维数与冲击强度之间拟合曲线的决定系数为0.9857，近似呈指数函数关系。研究结果为进一步深入研究芯壳结构竹塑复合材料的表面微观结构提供参考。
위료정량표정불동각층재료대심각결구죽소복합재료충격단구복잡정도적영향，이조지잉여물죽설화고밀도취을희（high density polyethylene，HDPE）작위심층재료，이순HDPE、죽장섬유/HDPE、납미탄산개/HDPE화백니/HDPE분별작위각층재료，채용용융공제공예제비심각결구죽소복합재료。재실온（23℃）배경하，측시료복합재료무결구충격강도，채용소묘전경대4충불동각층재료단구진행형모분석，기우분형이론화도상처리기술，운용상소점법계산료복합재료적충격단구표면분형유수，고찰료복합재료단구표면분형유수화충격강도적관계。결과표명，불동각층재료적심각결구죽소복합재료충격단구표면분형유수존재일정차이，각층위HDPE적복합재료단구표면분형유수최대，위2.2204，각층위백니/ HDPE적분형유수최소，위2.2075。불동각층복합재료충격단구표면분형유수의합곡선적결정계수균대우0.98，설명복합재료단구표면분형특정현저。병차，복합재료단구표면분형유수여충격강도지간의합곡선적결정계수위0.9857，근사정지수함수관계。연구결과위진일보심입연구심각결구죽소복합재료적표면미관결구제공삼고。
In order to study the rupture mechanism of the bamboo plastic composites (BPCs) with core-shell structure, in this paper bamboo residue fibers and high density polyethylene (HDPE) were used as materials of core layer; HDPE, bamboo pulp fibers/HDPE, nano-CaCO3/HDPE and white mud/HDPE, were respectively used as materials of shell layer to manufacture the BPCs with core-shell structure by coextrusion technology. The ratios of bamboo pulp fibers, nano-CaCO3 and white mud to HDPE in the shell layer structure were to be 10:90 respectively. To present the theoretical relationship between fractal dimensions (D) and the impact strength (δ), and analyze the effects of different shell layer materials on the impact strength in the BPCs with core-shell structure, Charpy non-notched impact strength of the BPCs with core-shell structure was measured at room temperature according to ASTMD6110-2010. The fractographs of the BPCs with core-shell structure that had different shell layer materials were observed by scanning electron microscope (SEM). The impact fracture surface topography of BPCs manifested self-similarity. Based on fractal theory and computer image processing technology, a MATLAB program which computed the fracture’s box-counting dimension of the BPCs with core-shell structure was designed. The digital image was transformed into factual image, and the charpy impact fracture surface fractal dimensions of the BPCs with core-shell structure that had different shell layer materials were measured by pixel-covering method, to investigate the relationship between impact strength and fractal dimension of the BPCs with core-shell structure. Results showed that the BPCs fracture possessed fractal characteristics and there were differences for the fractal dimensions of the BPCs with core-shell structure that had different shell layer materials. The fractal dimensions of the fracture surface were within the range of from 2.2075 to 2.2204, the linear degree of fitted beeline of MATLAB program was high and the correlation coefficients obtained were more than 0.98. The strong linear correlation indicated that impact fracture surface of the BPCs with core-shell structure had significant fractal characteristics. The impact fracture topography of HDPE in the shell layer was the most complicated in 4 kinds of fractures of the BPCs with core-shell structure, and the fractal dimension was up to 2.2204; the impact fracture topography of white mud/HDPE in the shell layer was more regular, and the fractal dimension was the smallest. The results accorded with the observed results by human eyes. The impact strength of the BPCs with core-shell structure containing HDPE shell layer material was the best and that containing white mud/HDPE had the worst performances. And the relationship between impact strength and fracture surface fractal dimension of the BPCs with core-shell structure obeyed exponential function roughly. Thus using the fractal dimensions to describe the impact fracture surface morphology of the BPCs with core-shell structure may provide a new approach to investigate the inherence rule between fractal characteristics and charpy impact strength of the BPCs with core-shell structure.