1、什么是膠合板？

膠合板(ban)(ban)(ban)(ban)(ban)是一種人造板(ban)(ban)(ban)(ban)(ban)，是將原木沿年輪方(fang)向旋切成(cheng)(cheng)大張(zhang)單板(ban)(ban)(ban)(ban)(ban)，經干燥、涂膠后按(an)相鄰單板(ban)(ban)(ban)(ban)(ban)層(ceng)木紋(wen)方(fang)向相互垂直的原則(ze)組坯(pi)、膠合而成(cheng)(cheng)的板(ban)(ban)(ban)(ban)(ban)材(cai)。單板(ban)(ban)(ban)(ban)(ban)層(ceng)數為(wei)(wei)奇數，一般為(wei)(wei)三(san)(san)(san)層(ceng)至十(shi)三(san)(san)(san)層(ceng)，常(chang)見的有三(san)(san)(san)合板(ban)(ban)(ban)(ban)(ban)、五合板(ban)(ban)(ban)(ban)(ban)、九合板(ban)(ban)(ban)(ban)(ban)、和(he)十(shi)三(san)(san)(san)合板(ban)(ban)(ban)(ban)(ban)（市場(chang)上俗稱(cheng)(cheng)為(wei)(wei)三(san)(san)(san)厘(li)板(ban)(ban)(ban)(ban)(ban)，五厘(li)板(ban)(ban)(ban)(ban)(ban)，九厘(li)板(ban)(ban)(ban)(ban)(ban)，十(shi)三(san)(san)(san)厘(li)板(ban)(ban)(ban)(ban)(ban)）。外層(ceng)的正面單板(ban)(ban)(ban)(ban)(ban)稱(cheng)(cheng)為(wei)(wei)面板(ban)(ban)(ban)(ban)(ban)，反面的稱(cheng)(cheng)為(wei)(wei)背板(ban)(ban)(ban)(ban)(ban)，內(nei)層(ceng)板(ban)(ban)(ban)(ban)(ban)稱(cheng)(cheng)為(wei)(wei)芯板(ban)(ban)(ban)(ban)(ban)。

2、分類：

一類膠合板為耐氣候、耐沸(fei)水膠合板，由此及彼有耐久、耐高溫，能蒸汽處理(li)的優點；

二類(lei)膠(jiao)合板為耐(nai)水膠(jiao)合板，能在冷水中浸漬(zi)和(he)短時間熱水浸漬(zi)；

三類(lei)膠(jiao)合(he)板(ban)為耐(nai)潮膠(jiao)合(he)板(ban)，能在冷水中(zhong)短時間(jian)浸漬，適(shi)于室內常溫(wen)下(xia)使用(yong)。用(yong)于家具和一般(ban)建(jian)筑用(yong)途(tu)；

四類合(he)板(ban)為不耐潮(chao)膠合(he)板(ban)，在室內常(chang)態下使用(yong)，一般(ban)用(yong)途膠合(he)板(ban)用(yong)材有櫸木(mu)(mu)、椴(duan)木(mu)(mu)、水曲柳、樺木(mu)(mu)、榆木(mu)(mu)、楊(yang)木(mu)(mu)等。

3、對稱原則：

對(dui)(dui)稱中(zhong)心(xin)(xin)(xin)平(ping)面(mian)(mian)兩側的(de)(de)單(dan)板(ban)，無論樹種，單(dan)板(ban)厚度、層數、制造方法、纖維方向和單(dan)板(ban)的(de)(de)含(han)水率(lv)都應(ying)該互(hu)相(xiang)對(dui)(dui)應(ying)，即對(dui)(dui)稱原則。膠(jiao)合(he)板(ban)中(zhong)心(xin)(xin)(xin)平(ping)面(mian)(mian)兩側各對(dui)(dui)應(ying)層不(bu)同方向的(de)(de)應(ying)力大小相(xiang)等(deng)(deng)。因此(ci)，當膠(jiao)合(he)板(ban)含(han)水率(lv)變化(hua)時，其(qi)結構穩(wen)定，不(bu)會(hui)產生變形，開裂(lie)等(deng)(deng)缺陷；反之，如果對(dui)(dui)稱中(zhong)心(xin)(xin)(xin)平(ping)面(mian)(mian)兩側對(dui)(dui)應(ying)層有某些差異，將會(hui)使(shi)對(dui)(dui)稱中(zhong)心(xin)(xin)(xin)平(ping)面(mian)(mian)兩側單(dan)板(ban)的(de)(de)應(ying)力不(bu)相(xiang)等(deng)(deng)，使(shi)膠(jiao)合(he)板(ban)產生變形、開裂(lie)。

4、奇數層原則：

由于膠合板(ban)(ban)(ban)的結構是(shi)(shi)相(xiang)鄰(lin)層(ceng)(ceng)單板(ban)(ban)(ban)的纖維方向互相(xiang)垂(chui)，又必(bi)須(xu)符合對稱原(yuan)則，因此它的總層(ceng)(ceng)數(shu)必(bi)定是(shi)(shi)奇數(shu)。如：三層(ceng)(ceng)板(ban)(ban)(ban)、五(wu)層(ceng)(ceng)板(ban)(ban)(ban)、七層(ceng)(ceng)板(ban)(ban)(ban)等。奇數(shu)層(ceng)(ceng)膠合板(ban)(ban)(ban)彎曲(qu)(qu)時大的水平剪應力(li)作(zuo)用(yong)在(zai)中心單板(ban)(ban)(ban)上(shang)，使其有較大的強度(du)(du)。偶數(shu)層(ceng)(ceng)膠合板(ban)(ban)(ban)彎曲(qu)(qu)時大的水平剪應力(li)作(zuo)用(yong)在(zai)膠層(ceng)(ceng)上(shang)而不是(shi)(shi)作(zuo)用(yong)在(zai)單板(ban)(ban)(ban)上(shang)，易使膠層(ceng)(ceng)破(po)壞，降低了膠合板(ban)(ban)(ban)強度(du)(du)。