1、什么是膠合板？

膠(jiao)合板(ban)(ban)(ban)是(shi)一種(zhong)人(ren)造板(ban)(ban)(ban)，是(shi)將原木(mu)沿年輪方向旋切成大張單(dan)(dan)板(ban)(ban)(ban)，經干燥、涂膠(jiao)后按(an)相(xiang)(xiang)鄰單(dan)(dan)板(ban)(ban)(ban)層(ceng)木(mu)紋方向相(xiang)(xiang)互垂直(zhi)的(de)(de)原則組坯(pi)、膠(jiao)合而成的(de)(de)板(ban)(ban)(ban)材。單(dan)(dan)板(ban)(ban)(ban)層(ceng)數為(wei)(wei)(wei)奇(qi)數，一般為(wei)(wei)(wei)三層(ceng)至十三層(ceng)，常(chang)見(jian)的(de)(de)有三合板(ban)(ban)(ban)、五合板(ban)(ban)(ban)、九合板(ban)(ban)(ban)、和十三合板(ban)(ban)(ban)（市場上俗稱為(wei)(wei)(wei)三厘(li)板(ban)(ban)(ban)，五厘(li)板(ban)(ban)(ban)，九厘(li)板(ban)(ban)(ban)，十三厘(li)板(ban)(ban)(ban)）。外層(ceng)的(de)(de)正面(mian)(mian)單(dan)(dan)板(ban)(ban)(ban)稱為(wei)(wei)(wei)面(mian)(mian)板(ban)(ban)(ban)，反面(mian)(mian)的(de)(de)稱為(wei)(wei)(wei)背板(ban)(ban)(ban)，內層(ceng)板(ban)(ban)(ban)稱為(wei)(wei)(wei)芯板(ban)(ban)(ban)。

2、分類：

一(yi)類膠(jiao)合(he)板為耐(nai)(nai)氣候、耐(nai)(nai)沸水膠(jiao)合(he)板，由(you)此及彼有耐(nai)(nai)久(jiu)、耐(nai)(nai)高溫，能蒸汽處理的優點(dian)；

二類(lei)膠(jiao)合板(ban)(ban)為耐水膠(jiao)合板(ban)(ban)，能在冷水中浸(jin)漬和短時間熱水浸(jin)漬；

三類(lei)膠合(he)板為耐(nai)潮膠合(he)板，能在冷(leng)水中(zhong)短(duan)時間浸漬，適(shi)于(yu)室內常溫(wen)下使用(yong)。用(yong)于(yu)家具和一般建筑(zhu)用(yong)途；

四類合板為不耐潮膠合板，在室內常態下使(shi)用(yong)(yong)，一般用(yong)(yong)途(tu)膠合板用(yong)(yong)材有櫸木(mu)、椴木(mu)、水曲柳、樺(hua)木(mu)、榆木(mu)、楊木(mu)等。

3、對稱原則：

對稱(cheng)中(zhong)心(xin)平面兩側的(de)單(dan)板(ban)，無論樹種，單(dan)板(ban)厚(hou)度(du)、層(ceng)數、制造(zao)方法、纖維方向和單(dan)板(ban)的(de)含(han)水(shui)率都應(ying)該互相(xiang)對應(ying)，即對稱(cheng)原(yuan)則。膠(jiao)(jiao)合(he)板(ban)中(zhong)心(xin)平面兩側各對應(ying)層(ceng)不(bu)同(tong)方向的(de)應(ying)力大(da)小相(xiang)等(deng)。因此(ci)，當膠(jiao)(jiao)合(he)板(ban)含(han)水(shui)率變(bian)化(hua)時，其(qi)結構穩定，不(bu)會產生變(bian)形，開裂等(deng)缺(que)陷；反之，如果對稱(cheng)中(zhong)心(xin)平面兩側對應(ying)層(ceng)有某些差異，將會使對稱(cheng)中(zhong)心(xin)平面兩側單(dan)板(ban)的(de)應(ying)力不(bu)相(xiang)等(deng)，使膠(jiao)(jiao)合(he)板(ban)產生變(bian)形、開裂。

4、奇數層原則：

由于膠(jiao)(jiao)合(he)(he)板(ban)(ban)(ban)的(de)(de)結構是相鄰層(ceng)單(dan)板(ban)(ban)(ban)的(de)(de)纖維方向互(hu)相垂，又必(bi)須符合(he)(he)對稱原則(ze)，因此它的(de)(de)總(zong)層(ceng)數必(bi)定是奇(qi)數。如：三層(ceng)板(ban)(ban)(ban)、五層(ceng)板(ban)(ban)(ban)、七(qi)層(ceng)板(ban)(ban)(ban)等。奇(qi)數層(ceng)膠(jiao)(jiao)合(he)(he)板(ban)(ban)(ban)彎曲時大的(de)(de)水平(ping)剪應力作(zuo)用在(zai)中心(xin)單(dan)板(ban)(ban)(ban)上，使(shi)其有較大的(de)(de)強度。偶數層(ceng)膠(jiao)(jiao)合(he)(he)板(ban)(ban)(ban)彎曲時大的(de)(de)水平(ping)剪應力作(zuo)用在(zai)膠(jiao)(jiao)層(ceng)上而不是作(zuo)用在(zai)單(dan)板(ban)(ban)(ban)上，易使(shi)膠(jiao)(jiao)層(ceng)破壞，降低了(le)膠(jiao)(jiao)合(he)(he)板(ban)(ban)(ban)強度。