1、什么是膠合板?
膠合(he)(he)(he)板(ban)(ban)(ban)(ban)(ban)是(shi)一種人造(zao)板(ban)(ban)(ban)(ban)(ban),是(shi)將原木沿年輪方(fang)向旋切成大(da)張單板(ban)(ban)(ban)(ban)(ban),經干燥(zao)、涂膠后(hou)按(an)相鄰(lin)單板(ban)(ban)(ban)(ban)(ban)層(ceng)(ceng)木紋方(fang)向相互(hu)垂直的原則組坯、膠合(he)(he)(he)而成的板(ban)(ban)(ban)(ban)(ban)材(cai)。單板(ban)(ban)(ban)(ban)(ban)層(ceng)(ceng)數(shu)為(wei)奇數(shu),一般為(wei)三層(ceng)(ceng)至十三層(ceng)(ceng),常見的有三合(he)(he)(he)板(ban)(ban)(ban)(ban)(ban)、五合(he)(he)(he)板(ban)(ban)(ban)(ban)(ban)、九(jiu)合(he)(he)(he)板(ban)(ban)(ban)(ban)(ban)、和十三合(he)(he)(he)板(ban)(ban)(ban)(ban)(ban)(市場上俗(su)稱為(wei)三厘(li)(li)板(ban)(ban)(ban)(ban)(ban),五厘(li)(li)板(ban)(ban)(ban)(ban)(ban),九(jiu)厘(li)(li)板(ban)(ban)(ban)(ban)(ban),十三厘(li)(li)板(ban)(ban)(ban)(ban)(ban))。外層(ceng)(ceng)的正面單板(ban)(ban)(ban)(ban)(ban)稱為(wei)面板(ban)(ban)(ban)(ban)(ban),反面的稱為(wei)背板(ban)(ban)(ban)(ban)(ban),內層(ceng)(ceng)板(ban)(ban)(ban)(ban)(ban)稱為(wei)芯(xin)板(ban)(ban)(ban)(ban)(ban)。
2、分類:
一類膠(jiao)(jiao)合(he)板(ban)為耐(nai)氣候、耐(nai)沸水(shui)膠(jiao)(jiao)合(he)板(ban),由(you)此(ci)及彼有耐(nai)久、耐(nai)高溫,能蒸汽處理的優點;
二類(lei)膠合(he)板(ban)(ban)為耐水(shui)膠合(he)板(ban)(ban),能在冷水(shui)中(zhong)浸(jin)漬(zi)和短時(shi)間熱水(shui)浸(jin)漬(zi);
三類膠合(he)板(ban)為耐潮膠合(he)板(ban),能(neng)在冷(leng)水中短時間(jian)浸漬,適于(yu)室內常溫下(xia)使用(yong)(yong)(yong)。用(yong)(yong)(yong)于(yu)家具和一般(ban)建筑用(yong)(yong)(yong)途(tu);
四類合(he)板(ban)為不耐潮膠合(he)板(ban),在室內常態下(xia)使用,一(yi)般用途膠合(he)板(ban)用材(cai)有(you)櫸木、椴木、水曲(qu)柳、樺木、榆木、楊木等(deng)。
3、對稱原則:
對稱(cheng)中心(xin)平(ping)面兩(liang)側(ce)的單(dan)(dan)板(ban)(ban)(ban),無論樹(shu)種,單(dan)(dan)板(ban)(ban)(ban)厚度、層(ceng)數、制造方法、纖維方向(xiang)(xiang)和(he)單(dan)(dan)板(ban)(ban)(ban)的含水(shui)率都應該互相(xiang)對應,即對稱(cheng)原則。膠(jiao)(jiao)合板(ban)(ban)(ban)中心(xin)平(ping)面兩(liang)側(ce)各對應層(ceng)不同(tong)方向(xiang)(xiang)的應力(li)(li)大小相(xiang)等。因此(ci),當膠(jiao)(jiao)合板(ban)(ban)(ban)含水(shui)率變化時(shi),其(qi)結構穩(wen)定,不會產生(sheng)變形,開(kai)裂等缺陷(xian);反之,如果對稱(cheng)中心(xin)平(ping)面兩(liang)側(ce)對應層(ceng)有某些(xie)差異,將會使對稱(cheng)中心(xin)平(ping)面兩(liang)側(ce)單(dan)(dan)板(ban)(ban)(ban)的應力(li)(li)不相(xiang)等,使膠(jiao)(jiao)合板(ban)(ban)(ban)產生(sheng)變形、開(kai)裂。
4、奇數層原則:
由于膠(jiao)(jiao)合板(ban)(ban)的(de)(de)(de)結構是相(xiang)鄰層(ceng)(ceng)單(dan)板(ban)(ban)的(de)(de)(de)纖維方(fang)向(xiang)互(hu)相(xiang)垂,又必(bi)須(xu)符合對(dui)稱原(yuan)則,因此它的(de)(de)(de)總層(ceng)(ceng)數必(bi)定是奇數。如(ru):三層(ceng)(ceng)板(ban)(ban)、五層(ceng)(ceng)板(ban)(ban)、七層(ceng)(ceng)板(ban)(ban)等(deng)。奇數層(ceng)(ceng)膠(jiao)(jiao)合板(ban)(ban)彎曲時(shi)大(da)的(de)(de)(de)水平剪(jian)應力(li)作用(yong)(yong)在(zai)中心單(dan)板(ban)(ban)上,使(shi)其有較大(da)的(de)(de)(de)強度。偶數層(ceng)(ceng)膠(jiao)(jiao)合板(ban)(ban)彎曲時(shi)大(da)的(de)(de)(de)水平剪(jian)應力(li)作用(yong)(yong)在(zai)膠(jiao)(jiao)層(ceng)(ceng)上而不是作用(yong)(yong)在(zai)單(dan)板(ban)(ban)上,易使(shi)膠(jiao)(jiao)層(ceng)(ceng)破壞,降低了膠(jiao)(jiao)合板(ban)(ban)強度。