碳纤维杆--碳纤维的结构介绍

        碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)是(shi)含(han)碳(tan)(tan)(tan)量高(gao)于(yu)90%的(de)(de)(de)(de)无机高(gao)分子纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)。其中含(han)碳(tan)(tan)(tan)量高(gao)于(yu)99%的(de)(de)(de)(de)称石墨纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)。碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)的(de)(de)(de)(de)微观结(jie)构类似(si)人(ren)造石墨，是(shi)乱层(ceng)(ceng)石墨结(jie)构。碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)各(ge)层(ceng)(ceng)面(mian)(mian)间(jian)(jian)(jian)的(de)(de)(de)(de)间(jian)(jian)(jian)距约为(wei)3.39到3.42A，各(ge)平行层(ceng)(ceng)面(mian)(mian)间(jian)(jian)(jian)的(de)(de)(de)(de)各(ge)个(ge)碳(tan)(tan)(tan)原(yuan)子，排列不(bu)如石墨那样(yang)规整(zheng)，层(ceng)(ceng)与(yu)层(ceng)(ceng)之间(jian)(jian)(jian)借范德华力(li)(li)连(lian)接在一起。 通(tong)常也把碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)的(de)(de)(de)(de)结(jie)构看(kan)(kan)成由两维(wei)(wei)(wei)(wei)(wei)(wei)有序(xu)的(de)(de)(de)(de)结(jie)晶和(he)(he)孔(kong)(kong)(kong)(kong)洞组成，其中孔(kong)(kong)(kong)(kong)洞的(de)(de)(de)(de)含(han)量、大(da)(da)(da)小和(he)(he)分布(bu)(bu)对(dui)碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)的(de)(de)(de)(de)性(xing)能(neng)(neng)影(ying)响(xiang)(xiang)较大(da)(da)(da)。当(dang)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)低于(yu)某个(ge)临界(jie)(jie)值(zhi)时(shi)，孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)对(dui)碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)复(fu)合材料(liao)的(de)(de)(de)(de)层(ceng)(ceng)间(jian)(jian)(jian)剪(jian)切强(qiang)度、弯曲强(qiang)度和(he)(he)拉伸强(qiang)度无明显(xian)的(de)(de)(de)(de)影(ying)响(xiang)(xiang)。有些(xie)研(yan)究(jiu)指出，引(yin)起材料(liao)力(li)(li)学(xue)性(xing)能(neng)(neng)下(xia)(xia)降(jiang)的(de)(de)(de)(de)临界(jie)(jie)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)是(shi)1%-4%。孔(kong)(kong)(kong)(kong)隙(xi)(xi)体积(ji)含(han)量在0-4%范围内时(shi)，孔(kong)(kong)(kong)(kong)隙(xi)(xi)体积(ji)含(han)量每增(zeng)加1%，层(ceng)(ceng)间(jian)(jian)(jian)剪(jian)切强(qiang)度大(da)(da)(da)约降(jiang)低7%。通(tong)过(guo)对(dui)碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)环氧树(shu)脂和(he)(he)碳(tan)(tan)(tan)纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)双(shuang)马(ma)来亚胺树(shu)脂层(ceng)(ceng)压(ya)板(ban)(ban)的(de)(de)(de)(de)研(yan)究(jiu)看(kan)(kan)出，当(dang)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)超过(guo)0.9%时(shi)，层(ceng)(ceng)间(jian)(jian)(jian)剪(jian)切强(qiang)度开(kai)始下(xia)(xia)降(jiang)。由试验得(de)知，孔(kong)(kong)(kong)(kong)隙(xi)(xi)主要(yao)分布(bu)(bu)在纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)束之间(jian)(jian)(jian)和(he)(he)层(ceng)(ceng)间(jian)(jian)(jian)界(jie)(jie)面(mian)(mian)处(chu)(chu)。并(bing)且孔(kong)(kong)(kong)(kong)隙(xi)(xi)含(han)量越高(gao)，孔(kong)(kong)(kong)(kong)隙(xi)(xi)的(de)(de)(de)(de)尺寸越大(da)(da)(da)，并(bing)显(xian)著降(jiang)低了层(ceng)(ceng)合板(ban)(ban)中层(ceng)(ceng)间(jian)(jian)(jian)界(jie)(jie)面(mian)(mian)的(de)(de)(de)(de)面(mian)(mian)积(ji)。当(dang)材料(liao)受力(li)(li)时(shi)，易沿层(ceng)(ceng)间(jian)(jian)(jian)破坏，这(zhei)也是(shi)层(ceng)(ceng)间(jian)(jian)(jian)剪(jian)切强(qiang)度对(dui)孔(kong)(kong)(kong)(kong)隙(xi)(xi)相对(dui)敏(min)感(gan)的(de)(de)(de)(de)原(yuan)因(yin)(yin)。另外孔(kong)(kong)(kong)(kong)隙(xi)(xi)处(chu)(chu)是(shi)应力(li)(li)集中区，承载能(neng)(neng)力(li)(li)弱，当(dang)受力(li)(li)时(shi)，孔(kong)(kong)(kong)(kong)隙(xi)(xi)扩大(da)(da)(da)形成长裂纹，从而遭到破坏。即使两种具有相同(tong)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)的(de)(de)(de)(de)层(ceng)(ceng)压(ya)板(ban)(ban)（在同(tong)一养护周期运(yun)用(yong)不(bu)同(tong)的(de)(de)(de)(de)预(yu)浸方法和(he)(he)制造方式(shi)），它们也表现(xian)(xian)处(chu)(chu)完全不(bu)同(tong)的(de)(de)(de)(de)力(li)(li)学(xue)行为(wei)。力(li)(li)学(xue)性(xing)能(neng)(neng)随孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)的(de)(de)(de)(de)增(zeng)加而下(xia)(xia)降(jiang)的(de)(de)(de)(de)具体数值(zhi)不(bu)同(tong)，表现(xian)(xian)为(wei)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)对(dui)力(li)(li)学(xue)性(xing)能(neng)(neng)的(de)(de)(de)(de)影(ying)响(xiang)(xiang)离散(san)性(xing)大(da)(da)(da)且重(zhong)复(fu)性(xing)差。由于(yu)包含(han)大(da)(da)(da)量可变因(yin)(yin)素，孔(kong)(kong)(kong)(kong)隙(xi)(xi)对(dui)复(fu)合材料(liao)层(ceng)(ceng)压(ya)板(ban)(ban)力(li)(li)学(xue)性(xing)能(neng)(neng)的(de)(de)(de)(de)影(ying)响(xiang)(xiang)是(shi)个(ge)很复(fu)杂的(de)(de)(de)(de)问题。这(zhei)些(xie)因(yin)(yin)素包含(han)：孔(kong)(kong)(kong)(kong)隙(xi)(xi)的(de)(de)(de)(de)形状、尺寸、位(wei)置；纤(xian)维(wei)(wei)(wei)(wei)(wei)(wei)、基(ji)体和(he)(he)界(jie)(jie)面(mian)(mian)的(de)(de)(de)(de)力(li)(li)学(xue)性(xing)能(neng)(neng)；静态或者动态的(de)(de)(de)(de)荷载。相对(dui)于(yu)孔(kong)(kong)(kong)(kong)隙(xi)(xi)率(lv)和(he)(he)孔(kong)(kong)(kong)(kong)隙(xi)(xi)长宽比，孔(kong)(kong)(kong)(kong)隙(xi)(xi)尺寸、分布(bu)(bu)对(dui)力(li)(li)学(xue)性(xing)能(neng)(neng)的(de)(de)(de)(de)影(ying)响(xiang)(xiang)更(geng)大(da)(da)(da)些(xie)。并(bing)发现(xian)(xian)大(da)(da)(da)的(de)(de)(de)(de)孔(kong)(kong)(kong)(kong)隙(xi)(xi)（面(mian)(mian)积(ji)>0.03mm2）对(dui)力(li)(li)学(xue)性(xing)能(neng)(neng)有不(bu)利影(ying)响(xiang)(xiang)，这(zhei)归因(yin)(yin)于(yu)孔(kong)(kong)(kong)(kong)隙(xi)(xi)对(dui)层(ceng)(ceng)间(jian)(jian)(jian)富胶区的(de)(de)(de)(de)裂纹扩展的(de)(de)(de)(de)产(chan)生影(ying)响(xiang)(xiang)。